CA2212240A1 - Guidance system with target line generation in virtual reality display - Google Patents

Abstract

A guidance apparatus including a mapping data receiver for receiving mapping data representing the coordinates of various points identifying a surface contour of at least one object in the space, memory for storing the coordinates, a position signal receiver operable to move in a path in the space and for receiving position signals indicative of at least first and second spacial positions of the position signal receiver, and a processor in communication with the mapping data receiver, the memory, and the position signal receiver. The processor is programmed to compute point positions of a plurality of respective target line segments, relative to the first and second spacial positions, to produce a representation of a target line extending from at least one of the first and second spacial positions. The point positions are computed such that the target line segments associated with respective point positions do not extend between the points representing the contour of any object represented by the mapping data stored in the memory at the time at least one point position is computed, such that each of the point positions is computed using mapping data available at the time when it is calculated. The processor further produces a signal representing a prediction of the path of the receiver as indicated by the point positions.

Description

GUIDANCE SYSTEM WITH TARGET LINE G~N~TION IN vlkluAL
REALITY DISPLAY

BACKGROUND OF THE lNv~NllON

This invention relates to devices for providing guidance to an operator of a vehicle to precisely navigate the vehicle over a work area. The invention may be used with agricultural machines such as sprayers, spreaders, seeders, etc., and for machines used in land planing and profiling such as graders, scrapers and bulldozers. The invention can also be applied in the forest industry, mining industry and in marine applications.

Currently, to navigate a vehicle over a field in order to spray pesticides or fertilizer over crops a vehicle operator must be careful not to re-spray a sprayed area and not to overestimate or underestimate the overlap of the spray on successive passes~
Some of the chemicals used for spraying are very difficult to see, which forces vehicle operators to try to remember the exact path and spray widths used for each pass over the field. When the field includes obstacles that must be avoided while driving, or, if the operator has few landmarks with which to navigate, the chances of over-spraying or under-spraying areas of the field are greatly increased, resulting in wastage of chemicals and un-sprayed areas.
If the vehicle operator stops work due to weather or time constraints and returns to spraying the field at a later date or time, the operator has no way of knowing exactly which areas have already been sprayed.
The agricultural industry has addressed this problem by using a foam dispenser positioned on a distal end portion of a boom to dispense foam to mark an outer edge of a work area traversed by the sprayer or other agricultural implement. An operator of the implement can then see lines of foam marking sprayed or worked boundaries. Foam markers, however, are affected by weather conditions such as rain and the like and have only a temporary presence.
In addition, foam markers can only be used when there is enough light to enable the operator to see them and, therefore, they may be unsatisfactory at night.
Other solutions include GPS-based navigation systems, which compute the position of the vehicle or implement from satellite signals. Computations are then performed to present the vehicle operator with guidance information.
Currently available systems provide guidance information by suggesting a system of parallel paths to cover a work area.
Such systems are ineffective in work areas where driving paths will be not parallel to each other. Non-parallel path operation can be important for irregularly shaped work areas with obstacles.

In addition, some GPS systems include only a digital map display, which presents the position of the vehicle, completed work, work to be completed, and work area landmarks. This type of display is useful for navigation in the field, but is difficult to use for guidance because it is difficult to make decisions about future directions and turns.

Other systems employ a light bar display. A light bar display indicates to the vehicle operator any deviation of the current vehicle position relative to a path that the vehicle should follow. This type of indicator also fails to notify the operator of upcoming turns, which is important if the path is not straight. This can lead to operator fatigue.

object derived from the coordinates of various points on the surface of the object.

Preferably, the processor is programmed to produce a virtual reality representation of the space, as seen from the viewpoint in the direction of the heading, the virtual reality representation including a representation of at least one object, derived from the coordinates of various points on the surface of the object.
Preferably, the processor is programmed to simultaneously produce the virtual reality representation and a plan view of the space.

Preferably, the processor is programmed to receive mapping data representing the coordinates of various points on respective surfaces of a plurality of objects in the space, to store the coordinates in memory and to produce respective representations of each of the objects in the visual representation such that the user can view the respective representations simultaneously.

Preferably, the processor is programmed to identify coordinates of an area representing at least a portion of the space, to identify objects within the area, and to send to the display commands including the coordinates of surfaces of objects within the area.

Preferably, the processor is programmed to compute point positions of a plurality of respective target line segments, relative to the first and second spacial positions, to produce a representation of a target line extending at a first pre-defined distance from at least one of the first and second spacial positions, the point positions being computed such that the target line segments associated with respective point positions do not extend between points representing the surface of an object.

It would therefore be desirable to have a device which allows the vehicle operator to observe a graphical representation of the work area, including completed work, the path the operator should follow to complete the work, area landmarks and a representation of further directions and turns. It would also be desirable for the device to be capable of providing guidance in irregularly shaped areas and for the device to be able to provide guidance for different driving modes, including parallel and spiral modes. It would also be desirable for the vehicle operator to observe a graphical representation of areas that have been sprayed and areas to be sprayed by providing a path on which to take the vehicle to optimize the spraying of a field to reduce over-spray and avoid un-sprayed areas. The present invention addresses this need.

BRIEF SU~$ARY OF THE l~v~;NllON
In accordance with one aspect of the invention, there is provided an apparatus for displaying a representation of an area in a space. The apparatus includes a mapping data receiver for receiving mapping data representing the coordinates of various points identifying a surface contour of at least one object in the space, memory for storing the coordinates, a position signal receiver operable to move in a path in the space and for receiving position signals indicative of at least first and second spacial positions of the position signal receiver, a display and a processor.
The processor is in communication with the mapping data receiver, the memory, the position signal receiver, and the display and is programmed to compute a heading of the receiver from the position signals. The processor is programmed to compute a viewpoint relative to at least one of the first and second spacial positions, and to produce commands recognizable by the display for causing the display to produce a visual representation of the space, as seen from the viewpoint in the direction of the heading.
The visual representation includes a representation of the Preferably, the processor is programmed to compute the point positions such that the point positions are no nearer than a safety distance to the object.

Preferably, the processor is programmed to compute the point positions such that the target line generally follows the contour of an object.

Preferably, the processor is programmed to produce a visual representation of the target line.

Preferably, the processor is programmed to update the visual representation as the receiver moves in the space.

lS In accordance with another aspect of the invention, there is provided guidance apparatus. The guidance apparatus includes a mapping data receiver for receiving mapping data representing the coordinates of various points identifying a surface contour of at least one object in the space, memory for storing the coordinates, a position signal receiver operable to move in a path in the space and for receiving position signals indicative of at least first and second spacial positions of the position signal receiver, and a processor in communication with the mapping data receiver, the memory, and the position signal receiver.
The processor is programmed to compute point positions of a plurality of respective target line segments, relative to the first and second spacial positions, to produce a representation of a target line extending from at least one of the first and second spacial positions. The point positions are computed such that the target line segments associated with respective point positions do not extend between the points representing the contour of any object represented by the mapping data stored in the memory at the time at least one point position is computed, such that each of the point positions is computed using mapping data available at the time at it is calculated. The processor further produces a signal representing a prediction of the path of the receiver as indicated by the point positions.

Preferably, the processor is programmed to receive and store new mapping data after at least one point position is computed such that the calculation of subsequent point positions is performed using the initial mapping data and the new mapping data.

Preferably, the processor is programmed to accumulate, in a completed work record, position points of the receiver, the position points representing positions which the receiver has traversed.

Preferably, the processor is programmed to accumulate a pre-defined number of position points in the completed work record and store the completed work record in a completed work list when the completed work record contains the pre-defined number of position points and to include the completed work list in the new mapping data.

Preferably, the processor is programmed to divide the initial mapping data and the new mapping data into sub-portions of coordinates of points representing the contours of surfaces of objects, where the surfaces of the objects are within a corresponding sub-portion of the space.

Preferably, the processor is programmed to compute the point positions such that the point positions are no nearer than the safety pre-defined distance to the object.

Preferably, the processor is programmed to compute the position of a viewpoint relative to at least one of the first and second spacial positions.
Preferably, the processor is programmed to compute from the position signals, a heading of the receiver.

Preferably, apparatus further includes a display and preferably the processor is programmed to produce display commands for causing the display to produce a visual representation of the target line.

Preferably, the visual representation includes a virtual reality representation of the space, as seen from the viewpoint in the direction of the heading, the virtual reality representation including the representation of the target line.

Preferably, the virtual reality representation includes a representation of at least one object derived from the coordinates of the various points representing the contour of the surface of the object.

Preferably, the processor is programmed to produce display commands which cause the display to simultaneously produce the virtual reality view and a plan view of the target line.

Preferably, the processor is programmed to update the prediction as the receiver moves in the space.

Preferably, the processor is programmed to compute the point positions such that the target line generally follows the contour of an object.

Preferably, the processor is programmed to receive and store in a mapping data list a plurality of pairs of coordinates identifying the surface of an object within the space, the pairs of coordinates representing heads and tails respectively of obstacle line segments approximating the surface of the object.
Preferably, the processor is programmed to identify coordinates of an area representing at least a portion of the space and identify pairs of coordinates in the mapping data list which are associated with objects within the area.

Preferably, the processor is programmed to identify coordinates of obstacles within the area and within a second pre-defined distance of a current point position.

Preferably, the processor is programmed to compute the point positions such that the target line segments associated with respective point positions do not cross obstacle line segments within the second pre-defined distance of the current position point.

Preferably, the processor is programmed to compute coordinates of a plurality of possible target line segments, to compare each target line segment with obstacle line segments within the second pre-defined distance of the current position point to determine whether any target line segment crosses an obstacle line segment, and to eliminate from the plurality of possible target line segments target line segments which cross obstacle line segments within the second pre-defined distance of the current position point.

Preferably, the processor is programmed to eliminate from the plurality of possible target line segments, each target line segment having a headpoint no nearer than a safety distance to the object.

Preferably, the processor is programmed to select coordinates identifying a target line segment nearest at least one obstacle line segment of the object as coordinates which identify a target line head segment.

Preferably, the processor is programmed to determine which of the target line segments has a head point corresponding to a position in space nearest to at least one of the first ~NI ~Y:YANCOUVER ;10- 9-97 ; 3:26PM ; 650 W. GEORGIA ST.~ 819 953 9538;# 2~ 9 and second spacial position~ of the receiver, a~ compared to the position~ in space of headpoints of remaining target line segment~.

Preferably, the proCe~Bor is proyrammed to determine coordinates of a new target line head segment when the di~tance between the point nearest to the spacial position o~ the receiver an~ the di~tal point i~ les~ than said fir~t pre-defined di~tance.
Preferably, ~he proce~or i~ programmed to delete the coordinates of a tar~et line tail ~egment of the target line when the coardinates of a new target line head ~3egrnent are deter~ined to maintain a target line having a pre-defined length.

In accordance with another aspect of the invention, there i~ provided a method of displaying ~ repre~entation of an area in a ~pace, the method i~cluding the ~teps of:
a) re~eiving m~pping data representing coordinate~
o~ va~iou~ point~ on a surface of at least one o~ject in the space and 6toring the coordinate~
in memory;
b) receivin~ po~ition signal~ indicative of at least fir~t and ~econd ~pacial position~ of a receiver operable to move and to rec~ive the po~ition ~ignals in the ~pace;
c) cornputing a heading o~ the receiver from the po~ition ~ignal~i ~ computing a viewpoint relative to at least one of 35the fir~t and ~econd ~pacial position~i and e) producing a visual representation of the space, as seen from the viewpoint in the direction of the heading, the visual representation including a representation of the object derived from the coordinates of various points on the surface of the object.

In accordance with another aspect of the invention, there is provided a method of guidance in a space, the method comprising the steps of:

a) receiving and storing in memory mapping data representing the coordinates of various points identifying a surface contour of at least one object in the space;

b) receiving position signals indicative of at least first and second spacial positions of a receiver operable to move in a path in the space, and operable to receive the position signals;

c) computing point positions of a plurality of respective target line segments, relative to the first and second spacial positions, to produce a representation of a target line extending from at least one of the first and second spacial positions, the point positions being computed such that the target line segments associated with respective point positions do not extend between the points representing the contour of any object represented by the mapping data stored in the memory at the time at least one point position is computed, such that each of the point positions is computed using mapping data available at the time at which the point positions are calculated; and d) producing a signal representing a prediction of the path of the receiver as indicated by the point positions.

In effect, the apparatus and method according to the invention provide a way of guiding a vehicle or even a hand-held receiver by predicting a path the vehicle or receiver is to take, on the basis of obstacle information which may be previously stored and which may be gathered during operation of the apparatus. The invention contemplates including a worked area as obstacle information, which allows the path of a farm vehicle, for example, to be predicted with the knowledge of where the vehicle has been, allowing the path to be predicted in such a manner that the vehicle avoids areas already traversed.
This has applications in spraying crops, for example, where the vehicle operator can be guided to avoid spraying areas already sprayed, without the need for markers and the like which are subject to weather conditions for visibility.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

In drawings which illustrate embodiments of the invention, Figure 1 is an overhead plan view of the work area according to the first embodiment of the invention;

Figure 2 is a block diagram of an apparatus according to the first embodiment of the invention;

Figure 3 is a view of a display showing a perspective view of a work area according to the first embodiment of the invention;

Figure 4a is a schematic diagram of a mapping data record format, according to the first embodiment of the invention;

Figure 4b is a schematic diagram of a target line list, according to the first embodiment of the invention;

Figure 4c is a schematic diagram of an obstacle list, according to the first embodiment of the invention;

Figure 4d is a schematic diagram of a heading list, according to the first embodiment of the invention;

Figure 4e is a schematic diagram of a target ray list, according to the first embodiment of the invention;
Figure 5 is a flow chart illustrating a main algorithm, according to the first embodiment of the invention;
~5 Figures 6a and 6b depict a flow chart of a previous work algorithm called by the main algorithm, according to the first embodiment of the invention;
~0 Figure 7 is a flow chart of a target line algorithm called by the main algorithm, according to the first embodiment of the invention;

Figure 8 is a flow chart of a closest segment algorithm called by the target line algorithm, according to the first embodiment of the invention;

Figure 9 is a flow chart of a point/segment distance algorithm according to the first embodiment of the invention;

Figure 10 i8 a flow chart of a target line segment algorithm called by the target line algorithm, according to the first embodiment of the invention;

Figure 11 is a schematic representation of a calculation of a new target line head segment according to the target line algorithm;

Figures 12a 12b, and 12c depict a flow chart of an obstacle routine called by the target line segment algorithm, according to the first embodiment of the invention;

Figure 13 is a flow chart of a segment crossing algorithm called by the obstacle routine, according to the first embodiment of the invention;

Figures 14a and 14b depict a flowchart of a bounding rectangle algorithm according to the first embodiment of the invention; and Figure 15 is a flowchart of a visible square algorithm according to the first embodiment of the invention.
DETAI~ED DESCRIPTION

Fiqure 1 Referring to Figure 1, a field is shown generally at 10.
The field is bounded by a ditch 12, a fence 14, a grove of trees 16 and a road 18. Within the field, there is a work CA 022l2240 l997-08-Ol area 20 in which a crop 22 is planted and in which there is a weed area 15.

The crop 22 is sprayed by employing a vehicle 24 such as a tractor to transport a spray boom 26 operable to spray insecticide, for example, over the work area 20 until the entire work area has been sprayed. It will be appreciated that the ditch 12, fence 14 and grove of trees 16 are landmarks which must be avoided by the vehicle and therefore must be treated as obstacles while the road 18, crop 22 and weed area 15 landmarks may be traversed by the vehicle 24 and are not considered obstacles. The spray boom 26 acts as a working device and may be replaced with other implements without departing from the scope of the invention.

According to this embodiment of the invention, the vehicle 24 is provided with a guidance apparatus 28 which guides an operator of the vehicle to transport the spray boom 26 over the work area 20 such that portions 29 of the work area already sprayed are not re-sprayed on successive passes over the work area.

Figure 2 Referring to Figure 2, a block diagram of the guidance apparatus 28, according to a first embodiment of the invention, is shown. The apparatus includes a GPS receiver shown generally at 32 and a computer 34.
The GPS receiver 32 includes a processor 36, an antenna 38, a position output 40, a time output 42 and a status output 44. The antenna 38 is operable to receive signals from a plurality of satellites in the conventional manner. These signals are then used by the processor 36 to determine geographical position coordinates of the antenna and to determine a quality value associated with the geographical position coordinates. The processor provides at the position output 40, position signals providing a digital representation of the geographical position coordinates in the World Geodetic System (1984) datum, provides at the time output 42 a digital representation of the time the position coordinates that were derived and provides at the status output 44 a digital representation of status information which allows the quality of the geographical position coordinates to be estimated.
The computer 34 includes a microprocessor 46, an Input/Output (I/O) port 48, a Random Access Memory (RAM) 50, a Read Only Memory (ROM) 52, a keypad 54, a display interface 56, and a display 58, all in communication with the microprocessor 46.

In this embodiment, the keypad 54 has a work control key 60, a driving mode key 62, a landmark control key 64, a map control key 66, a perspective view control key 67, a field control key 68 and a plurality of alphanumeric keys 69. The keypad also has a selection output 70. The keypad 54 is operable to provide signals representing an actuated key, at the selection output 70.

The display interface 56 includes a display control input 72 for receiving display command signals from the I/O port 48 under the control of the microprocessor 46 running a program entitled OpenGL, licensed by Microsoft Corporation.
The display interface 56 is operable to control the display 58 to simultaneously display a perspective view and an overhead mapping view of the work area, as will be explained below.

The I/O port 48 includes a display control output 74, a position input 76, a time signal input 78, a status signal input 80 and a selection input 82. The display control output 74 is connected to the display control input 72 to CA 022l2240 l997-08-Ol communicate display command signals from the I/O port 48 to the display control input 72 of the display interface 56.
The position input 76 is connected to the position output 40 for receiving the representation of the geographical position data from the GPS receiver 32. The time signal input 78 is connected to the time output 42 to receive the time signal from the GPS receiver 32 and the status signal input 80 is connected to the status output 44 for receiving from the GPS receiver 32 the representation of the quality of the position data. The selection input 82 is connected to the selection output 70 for receiving signals representing an actuated key of the keypad 54. The I/O
port thus acts as a receiver for receiving position signals indicative of a spacial position of the vehicle.
The I/O port 48 is in communication with the microprocessor 46 by a conventional address and data bus 47. The I/O port 48 has read and write registers 84, 86, 88, 90, and 92 which are associated with display control output 74 and inputs 76-82 respectively. By reading registers 86-90 in the I/O port 48, the microprocessor 46 is operable to read the geographical position data received at the position input 76, to read the time data received at the time signal input 78, to read the representation of the status received at the status signal input 80 and to read the signals representing an actuated key, received at the selection input 82. By writing to register 84, the microprocessor 46 is operable to provide display command signals at the display control output 74.
The ROM 52 has a plurality of registers in which are stored blocks of program instruction codes for directing the processor 46 to execute various algorithms. The stored blocks of code implement a main algorithm 94, a coordinate conversion algorithm 95 and a Kalman filter algorithm 96.
Within the blocks of code implementing the main algorithm are included sub-blocks which implement a previous work algorithm 98, a target line algorithm 100, a closest segment algorithm 104, a point/segment distance algorithm 106, a target line segment algorithm 108, an obstacle algorithm 110, a segment crossing algorithm 112, a bounding rectangle algorithm 111, and a visible square algorithm 116.

The coordinate conversion algorithm 95 is implemented by blocks of code which direct the microprocessor 46 to read data representing a latitude and a longitude coordinate in the World Geodetic System (1984) datum from the position register 86 and to apply a conversion function, as disclosed in ~GPS Satellite Surveying", 2nd Edition, by Alfred Leick, published by John Wiley & Sons, Inc., and incorporated herein by reference. The conversion function provides UTM coordinate data representing vehicle position in northing and easting coordinates, in the UTM coordinate system.

The Kalman filter algorithm 96 is of the type described in a book entitled "Applied Optimal Estimations", by Arthur Gelb et al., available from the I.T. Press, Cambridge Massachusetts incorporated herein by reference. In this embodiment, the Kalman filter algorithm uses an internal threshold distance value of one meter and, therefore, ignores any position data received from the GPS receiver, representing a change in position of less than one meter from an immediately previous position.

The microprocessor 46 is in communication with the ROM 52 and is operable to execute the program instructions of respective blocks of code to effect the functionality of the algorithms indicated.

Fiqure 3 Referring to Figure 3, the instruction codes according to the algorithms indicated in Figure 2 cooperate to direct the microprocessor to send signals to the display 58 to depict a perspective view 41 of the work area 30 to be sprayed by the spray boom 26. The perspective view 41 includes representations of physical landmarks including 5 the ditch 12, fence 14, weed 15 and grove of trees 16. The user identifies such landmarks prior to using the apparatus and enters information regarding these landmarks through the alphanumeric keys 69 on the keypad 54. In addition, such information may be entered while the apparatus is in use to cause the processor to store information relating to landmarks and to generate display commands to cause representations of such landmarks to be displayed on the display. Such display commands are provided in a format compatible with the OpenGL forming part of the display interface.

In addition to the display of landmarks, the instruction codes stored in the ROM 52 cooperate to direct the microprocessor 46 to produce display commands which cause the display to depict an indication of an area which has already been sprayed, in this embodiment, portion 29, so the operator can ascertain areas completed and areas which are yet to be completed. This is particularly important in spraying as typically, the operator cannot determine which areas have been sprayed simply by looking at the ground, as many sprays are invisible.

The instruction codes stored in the ROM 52 also cooperate to direct the microprocessor 46 to produce display commands which cause the display to depict a target pattern which, in this embodiment, includes a target line 43 having a plurality of target line segments 45, 55 including a head segment 49 and a tail segment 51. The target line 43 provides a visual indication to the operator, of a path on which to take the vehicle in order to spray the work area in view of work already completed. The target line segments 45, 55, etc., are calculated and displayed for an area sufficiently far ahead of the vehicle to provide advance notice to the operator, of any upcoming turns to avoid landmarks or obstacles.

Referring back to Figure 2, the RAM 50 is in communication with the microprocessor 46 and has a plurality of registers or buffers which the microprocessor uses to store data characterized and structured as positioning information 113, initial vehicle parameter list 114, a target line parameter list 118, a perspective view parameter list 120, an initial mapping data list 121, a user-inputted landmarks list 124, a completed work list 128, a mapping data list 122, a target line point list 126, a working device width buffer 130, a work control flag buffer 132, a smoothed position buffer 134, a smoothed heading buffer 136, an obstacle list 140, a heading list 142, a target ray list 146, temporary storage buffers 148, and a standard deviation limit buffer 149.

Positioninq Information The positioning information buffer 113 is used to store the representations of the GPS position, time and status information as received from the GPS receiver 32.

Initial Vehicle Parameter List The initial vehicle parameter list 114 includes fields (not shown) for storing data relating to vehicle width, position of driver~s seat, position of the centre of the working device, GPS antenna position, physical working device width and overlap. Overlap is calculated as the working device width less the actual distance between adjacent completed work. Overlap must be less than one-half all of the working device width. Generally, the initial vehicle parameter list fields are filled by the microprocessor 46 with data supplied by the user, which the user determines from known specifications of the vehicle, and which are entered by the user at the keypad. This is done before the CA 022l2240 l997-08-Ol main algorithm is executed. The driver's seat, the centre of the working device and the GPS antenna position data is provided in a Cartesian coordinate reference frame in meters utilizing the GPS antenna 38 as the origin with the 5 normal, forward direction of travel of the vehicle coincident with the positive y-axis.

Tarqet Line Parameter List The target line parameter list 118 includes fields (not shown) for storing data relating to the width of target line segments, segment length, forward length of target line, maximum target line length, number of rays, ray spacing, maximum deviation distance, initial observation angle and additional observation angle. The segment width 15 data specifies the width of the target line in relation to other physical objects to be displayed. The segment length data specifies the distance between the two end points of a target line segment, which in this embodiment, is one meter. In general, the segment length should be 20 approximately equal to the internal threshold distance used in the Kalman filter which effectively sets the resolution of the apparatus, indicating the minimum distance between points in the space to be represented on the display. The forward length of target line specifies the minimum 25 distance between the nearest segment to the vehicle and to the head of the target line, along the path of the target line, before a new segment is added to the target line.
The maximum target line length data specifies the maximum length of the target line in relation to other physical 3 0 objects to be displayed. The number of rays sets the number of rays that will be considered before constructing the target line and must always be an odd number. The ray spacing is automatically calculated by the microprocessor 46 when the user enters an initial observation angle, by 35 taking the quotient of the initial observation angle and the number of rays according to the following relation:

CA 022l2240 l997-08-Ol Observation Anqle = angular spacing value (a) (Number of Rays - 1) The maximum deviation distance sets a threshold on the distance the GPS antenna can move from the target line 5 before a new target line will be generated. The additional observation angle specifies an additional angle in which additional rays are calculated, beyond the initial observation angle. The target line parameter list is filled by the user before the main algorithm is executed, by entering data through the keypad 54. Generally data in the target line list is set according to the type of work and user preferences for the display of the target line.

Perspective View Parameter List 15 The perspective view parameter list 120 includes fields (not shown) for storing data relating to the distance from the viewer to the far clipping plane, the field of view angle in degrees in the horizontal direction, sky colour, ground colour, ground grid colour and grid spacing.

Initial MaPDinq Data List Referring to Figure 4a, the initial mapping data list 121 includes a plurality of records each having at least an identification field 91, position fields 93, attribute fields 102, and bounding rectangle fields 97. The ID field 91 is used to identify whether the record relates to a tree, rock, pole, building, surface, fence, previous work, etc. The position data fields 93 are used to store a plurality of x and y coordinates, or pairs of coordinates identifying a surface of an object within the space, the pairs of coordinates representing heads and tails respectively of landmark line segments approximating the surface and representing points no less than approximately one meter apart in this embodiment. In general, the distance between points need not be any less than the internal threshold distance used by the Kalman filter algorithm 96. The RAM 50 thus acts as a receiver for receiving and storing pairs of coordinates in a mapping data list. The attribute fields 102 include fields for storing geometrical attributes, in this embodiment sizes and safety distances and for storing physical attributes, for example colour, contrast and barrier/non-barrier information. Barrier/non-barrier information relates to whether or not the object to which the record relates acts as a barrier to the vehicle. The bounding rectangle fields 97 are used to store maximum northing, minimum northing, maximum easting, minimum easting values as boundary values describing a bounding rectangle encompassing the object.
These are determined by locating the maximum and minimum northing and easting value of all of the coordinates in the record and storing the greatest northing value, greatest easting value, least northing value and least easting value and the boundary values. The processor is thus programmed to compute and store in memory, the coordinates of a bounding rectangle encompassing the surface of the object.
The memory thus acts as a mapping data receiver for receiving and storing mapping data representing the coordinates of various points identifying a surface contour of at least one object in the space.

User Inputted Landmark List The user-inputted landmarks list 124 includes a plurality of records having fields of the type described above for storing information regarding landmarks the user wishes to view on the display and/or may wish to avoid while driving.
While the apparatus is in use, information regarding landmarks is accumulated in the user-inputted landmark list. Thus, the processor is programmed to receive mapping data representing the coordinates of various points on a surface of an object in the space.

Completed Work List The completed work list 128 includes a plurality of completed work records having fields of the type described above for storing information regarding completed work.
S Each completed work record, however, is operable to store only a maximum of twenty-five position points. While the apparatus is in use, information regarding completed work is accumulated in the completed work list 128.

MapPinq Data List The mapping data list 122 includes a collection of records including the initial mapping data records, landmark records from previous operations of the apparatus and work records from previous operations of the apparatus.
Tarqet Line Point List Fiqure 4b Referring to Figure 4b, the target line point list 126 is used to store a plurality 127 of target line point records 129, 131, 133, each record having fields 135 and 137 for storing number pairs (X1, Y1) representing northing and easting coordinates respectively of a point. Each number pair represents a target line segment of the target line.
A finite number of number pairs are stored, this number depending on the forward length of the target line. The target line list further includes a target line headpoint index buffer 138 for storing a value identifying the target line point record in which is stored a number pair identifying the head of the target line. The target line list further includes a target line point index buffer 139 which is used to store a value representing a currently addressed target line point record. The target line point list further includes a target line heading buffer 119 used to store a number representing the current heading of the target line represented by the target line point records.

Workinq Device Width Buffer The working device width buffer 130, is used to store a value representing the width of the working device operated by the vehicle to work the work area. In this embodiment, the working device includes the spray boom 26.

Work Control Flaq Buffer The work control flag buffer 132, is used to store a value representing whether or not the working device is active.
The work control flag is set to active or inactive by the actuation of the work control key 60, in conjunction with the previous work algorithm 98.

Smoothed Position Buffer The smoothed position buffer 134 is used to store a number pair representing the current spacial position of the vehicle as derived by filtering raw position data from the positioning information buffer 113 under the Kalman filter algorithm 96.

Smoothed Headinq Buffer The smoothed heading buffer 136 is used to store a number derived by filtering raw position data from the positioning information buffer 113 under the Kalman filter algorithm 96.

Obstacle List Referring to Figure 4c, the obstacle list 140 includes an index field and plurality of obstacle segment records having first and second point fields for storing first and second points respectively, identifying a line segment of an obstacle.

Headinq List Referring to Figure 4d, the heading list 142 includes a plurality of heading fields 143 for storing values representing headings of the vehicle.

Tarqet RaY List Referring to Figure 4e, the target ray list 146 includes a ray index buffer 147 and a plurality of ray line point records 145, 151, etc, the actual number of rays being 5 specified by the contents of the number of rays field in the target line parameter list 118. Each ray line point record has fields 153, 155, for storing a number pair (xl,yl) representing an end point of a ray line segment.
The ray index buffer is used to hold a ray index value pointing to a currently addressed ray line point record.

Temporary Storaqe Buffers The temporary storage buffers 148 include first, second, third, fourth, fifth, and sixth temporary buffers. The 15 microprocessor 46 is operable to read and write data to each of these buffers.

Standard Deviation Limit Buffer The standard deviation limit buffer 149 is used to store a value representing a standard deviation limit for use in calculating whether or not a calculated standard deviation value exceeds the standard deviation limit.

The microprocessor 46 is programmed to follow a start-up 2 5 algorithm (not shown) under which the microprocessor is directed to store predetermined data into the buffers described above, and to clear the contents of the work control flag buffer 132. The processor is then directed to the blocks of code implementing the main algorithm 94.
Main Alqorithm Fiqure 5 Referring to Figure 5, generally, the main algorithm 94 directs the microprocessor to accept new position data from 35 the GPS receiver, accept new landmark data from the user, update the completed work list, produce a new target line segment if required, and update the display with the above information.

Referring to Figures 2 and 5, upon entry into the code implementing the main algorithm 94, block 150 directs the microprocessor 46 to read the position data from the position register 86, to read the time data from the time input register 88, and to read the status data from the status input register 90.
Block 157 then directs the microprocessor 46 to execute code implementing the coordinate conversion algorithm 95 using the position data obtained in block 150. The coordinate conversion algorithm 95 generates data representing the northing and easting coordinates, in the UTM position system, from the position data obtained in block 150.

Block 152 then directs the microprocessor 46 to execute code implementing the Kalman filter algorithm 96 using the position data obtained in block 157 and the time data and status data obtained in block 150. The Kalman filter algorithm 96 generates data representing a smoothed vehicle position and data representing a smoothed heading of the vehicle, based on current and past position data. As part of the Kalman filter algorithm, the microprocessor 46 stores the smoothed position data in the smoothed position buffer 134 and stores the heading data in the smoothed heading buffer 136. If the vehicle moves in reverse, the microprocessor 46 calculates the heading as the forward heading less 180 degrees and stores the calculated heading value in the smoothed heading buffer 136. If the vehicle stops, although the GPS will produce random positions due to the nature of GPS, the Kalman filter algorithm will recognize when the vehicle has stopped and will maintain the last heading before the vehicle stopped, in the smoothed heading buffer 136 and will maintain the last position value obtained before the vehicle stopped in the smoothed position buffer 134.

Block 154 then directs the microprocessor 46 to read the selection input register 92 to determine whether or not the landmark control key 64 has been actuated. If so, then block 156 directs the microprocessor 46 to store user-inputted landmark data in the user-inputted landmarks list 124, of Figure 4a. If the landmark control key 64 is not actuated, the microprocessor 46 is programmed to proceed with block 158 which directs the microprocessor 46 to read the contents of the work control flag buffer 132 to determine whether or not the work control flag is active.
If the work control flag is active the microprocessor 46 is programmed to proceed to block 160 which directs the microprocessor to call the previous work algorithm 98.
Otherwise, the microprocessor 46 is programmed to proceed to block 162 to again read the selection input register 92 to determine if the work control key 60 has been actuated.
If the work control key has been actuated, the microprocessor 46 is directed to proceed to block 160 where it calls the previous work algorithm 98. If the work control key has not been actuated or the previous work algorithm 98 has just been completed, the target line algorithm 100 is called at block 164 to produce a new target line.

Upon completion of the target line algorithm 100, block 166 directs the microprocessor 46 to call the visible s~uare algorithm 116 which directs the processor to send display commands to the display interface to cause the display of the perspective view 41 of at least a portion of the work area in a space, as viewed from the present position as determined from the smoothed position data and the smoothed heading data stored in the smoothed position and smoothed heading buffers 134 and 136 respectively. The display commands also cause the display of an overhead plan view, including the target line such as shown in Figure 1, of the area shown in the perspective view 41. The display is thus operable to simultaneously display the perspective view and a plan view of the target line. The main algorithm 94 is then repeated.

Previous work alqorithm Fiqures 6a and 6b Generally, the previous work algorithm 98 directs the microprocessor to load the completed work list with position and boom width information which is displayed, according to the main algorithm 94, as a sprayed or worked area in the overhead and perspective views shown in Figures 1 and 3 respectively.
Referring to Figures 2 and 6a, the previous work algorithm is shown generally at 98 and begins with block 168 which directs the microprocessor 46 to read the contents of the work control flag buffer 132 and to determine whether or 20 not it contains data representing an active state. If it does not, block 169 directs the processor to write data representing an active state into the work control flag buffer 132 to active. Referring to Figures 4a and 6b, block 171 then directs the processor to create a new 2 5 completed work record.

Block 173 then directs the processor to read the contents of the smoothed position buffer 134 and the contents of the working device width buffer 130 and to store these values in the first position field and in the attribute field respectively. Block 175 then directs the processor to clear the heading list 142. Block 177 then directs the processor to read the contents of the smoothed heading buffer 136 and to store the contents in the heading list 142. The previous work algorithm 98 is then ended. In other words, if the work control flag has not been previously set, a new work record is created and the heading list is initialized.

If at block 168 of Figure 6a, the work control flag buffer contains data representing an active state, block 170 directs the microprocessor 46 to read the contents of the selection input register 92 to determine whether or not the work control key has been actuated. If the work control key has been actuated, the microprocessor 46 is directed to proceed to block 174 which directs the microprocessor 46 to write data representing an inactive state into the work control flag buffer 132. Otherwise, if the work control key has not been actuated the microprocessor 46 is directed to proceed to block 179 which directs the microprocessor 46 to count the number of position data points stored in the current work record and to determine whether or not twenty-four points of position data are contained therein.

If there are twenty-four position data points in the work record, block 178 directs the processor to read the contents of the smoothed position buffer 134 and store the position stored therein in the work record. The work record then contains 25 positions and is considered to be a complete work record. Block 180 then directs the processor to compute bounding rectangle maximum and minimum points and store these points in thè completed work record. To do this, the processor is directed to determine the maximum X
value Xmax of all the points in the work record and the maximum Y value YmaX of all the points in the work record and to determine the minimum X value Xmin of the points in the work record and to determine the minimum Y value Ymin of all the points in the work record to produce two points identifying a bounding rectangle, the first point being specified by Xmin and Ymin and the second point being specified by Xmax and YmaX. The boundary points are then stored in the completed work record. Thus, the processor is programmed to compute bounding rectangle points SENT BY:VANCOUVER ;10- 9-97 ; 3:26~M ; 650 W. GEORGIA ST.~ 819 953 9538;# 3 repre~enting the coordinate~ of a bounding re~tangle encompa6sing the points in the completed work record and to ~tore the bounding rectan~le point~3 in as~30ciation with the c~mpleted work reco~d.

~lock 182 then direct~ the proce~or to ~tore t~e work re~o~d by appending it to the completed work list 128 of Figure 4a. The proce~sor i~ then directed to blocks 171 thr~ugh 177 shown in Figure 6b which set ~p a new ~lank completed work record, and the algori'chrn i8 ended. The ef~ect of block~ 17~, 178, 180, lB~ and 171-177 is to limit completed work re~ord~ ~o cont~in a maxi~um of twenty-five po~ition point~, to append completed work records having twenty-five po~ition points to the co~pleted work li~t and to create a new ~o~pleted work record each time a completed work record i8 appended to the completed work list. Thu~, the proce6~0r i~ pro~ra~med to accumulate, in a completed work record, poYition points of the vehicle, the po~ition poin~s repre~enting positions ~hich the vehicle ha~
traver~ed. In other word~, the proces~or i~ programmed to accumulate a predefined number of po6ition points in the completed work record and ~tore the completed work record in a completed work list when the completed work record colltaill~ the predefined number of po~ition point~.
Referring back to Figure ~, if at block 17~, there are les~ than 25 lap po~ition points in the completed work record, the proce~or i~ ~irected to block 176 which directs the proce~o~ to copy the heading ~t~red in the ~moothed heading buffer 136 into the heading li~t 142.
Block 184 ~hown in Figure 6~, then directs the proce~60r to calculate ~he ~tandard deviation of the content~ o~ the heading li~t 142 a~d to determine whethe~ or not such standard deviation is le~ than or equal to the content~ of the ~andard deviation limit buffer 149. If ~o, then the perviou~ work algorithm is ende~ and the current ~moothed pc~ition is not added to ~he co~pleted work record. If the standard deviation is not less than the limit, the processor is directed to blocks 173 through 177 which direct the processor to add the current smoothed position to the completed work record, clear the heading list 142 and add the current smoothed heading to the heading list 142. The algorithm is then ended.

Referring back to block 170 in Figure 6a, if at block 170 the work control key has been actuated then block 174 directs the processor to clear the work control flag by writing a null value to the work control flag buffer 132.

slock 188 then directs the processor to copy the contents of the smoothed position buffer 134 to the current completed work record.

Block 189 then directs the processor to determine the maximum X value Xm~ of all the points in the work record and the maximum Y value YmaX of all the points in the work record and to determine the minimum X value Xmin of all of the points in the work record and to determine the minimum Y
value Ymin of all the points in the work record to produce two points identifying a bounding rectangle, the first point being specified by Xmin and Yminand the second point being specified by X~ax and YmaX. The boundary points are then stored in the completed work record.

Block 191 then directs the processor to store the work record by appending it to the completed work list 128. The pervious work algorithm is then ended. Thus, the processor is programmed to accumulate points indicated by the position signals, the points representing an area traversed by the vehicle and the processor is programmed to accumulate the points in a work record having a finite length, the points identifying line segments of a work swath produced by the vehicle and the processor is programmed to store the work record in the completed work list, which is included in the mapping data list.

Tarqet Line Alqorithm Figure 7 Generally, the target line algorithm directs the microprocessor to produce a new target line if one has not already been produced. In addition, a segment will be added to a current target line if a headpoint of that segment does not lie within a predefined distance of an obstacle, as determined by the obstacle algorithm. When a target line is near an obstacle, any new segments will be added such that the segments follow the contour of the obstacle. In this embodiment, previous work is considered to be an obstacle and, therefore, if the apparatus is used in a field with an obstacle such as a retangular fence which acts as a boundary between which the vehicle is driven, the proximity of the previous work and the fence as obstacles will result in the target pattern being generated as a rectangular serpentine line. If the vehicle position is such that the vehicle is surrounded by obstacles, target line generation is halted. This situation may occur when all work in the field has been completed. Finally, if the vehicle's position exceeds a predefined distance from the target line, a new target line beginning at the vehicle's position will be initiated. This could occur if the vehicle makes a 180-degree turn to pursue a new direction at the boundary of the field and continues to proceed in that new direction until the vehicle's position exceeds the predefined distance from the target line headpoint.

Referring to Figures 2, 4b and 7, in the target line algorithm 100, block 190 directs the microprocessor 46 to determine whether or not a target line has already been produced by reading the contents of the target line point list 126 to determine whether or not the target line point record addressed by the target line headpoint index buffer 138 shown in Figure 4b, contains a null value. If so, then it is considered that no valid data is stored in the target line point list 126 and the microprocessor 46 is directed to block 192 which directs the microprocessor 46 to initialize the target line by storing the contents of the smoothed heading buffer 136 in the target line heading buffer 119, storing the contents of the smoothed position buffer 134 in the first target line point record 129 of the target line point list 126 and by setting the contents of the target line headpoint index buffer 138 and the contents of the target line point index field to point to the first target line point record 129.

If at block 190 the target line point record addressed by the target line headpoint index buffer 138 does not contain a null value, block 194 directs the microprocessor 46 to call the closest segment algorithm 104 shown in Figure 8, to determine which target line segment is nearest the vehicle's position.
Closest Seqment Alqorithm The closest segment algorithm directs the microprocessor to determine which of the line segments forming the target line is closest to the present position of the vehicle.
Referring to Figure 8, the closest segment algorithm 104 begins with block 300 which sets the contents of the target line point index buffer 139 to that of the target line headpoint index buffer 138. Block 302 then directs the processor to retrieve from the target line point list 126 a first point addressed by the target line point index buffer 139 and a second point immediately preceding the point addressed by the target line point index buffer 139.
The first and second points thus represent a head and tail respectively of a target line segment. In addition, the microprocessor 46 is directed to retrieve and store in a the first temporary buffer of the temporary storage buffers 148, the number pair representing the vehicle's position, from the smoothed position buffer 134. Block 304 then directs the microprocessor to call the point/segment distance algorithm 106 shown in Figure 9.

Point/Seqment Alqorithm Fiqure 9 Referring to Figure 9, the point/segment distance algorithm 106 directs the microprocessor to calculate the distance between a given point and a given line segment, where the line segment may be a line segment of an obstacle or a segment of the target line.

Referring to Figure 9, the point/segment distance algorithm 106 begins with block 204 which directs the microprocessor 46 to calculate a difference in X-coordinates, and a difference in Y-coordinates for the segment, a segment length and a distance value from the segment to the point.
The difference in X-coordinates, DX is calculated according to the relation:

X=X2-X1 where X1 is the contents of the temporary register holding the X-coordinate of the first point of the segment; and X2 is the contents of the temporary register holding the X-coordinate of the second point 3 0 of the segment.

The difference in X-coordinates, DX, is stored in the second temporary buffer of the temporary storage buffers 148. The difference in Y-coordinates is calculated according to the equation:

DY=Y2-Y1 where Y1 is the content of the temporary register holding the Y coordinate of the first part of the segment; and Y2 is the content of the temporary register holding the Y coordinate of the second point of the segment.
The difference in Y-coordinates, DY, is stored in the third temporary buffer of the temporary storage buffers 148.

The segment length, L, is calculated from the difference in Y-coordinates of the segment and the difference is X-coordinates of the segment, using the following relation:

L=sqrt (DX*DX+DY*DY) The calculated segment length value, L, is stored in the fourth temporary buffer of the temporary storage buffers 148.
The distance, D, from the line segment to the point is calculated according to the following relation:
D=(X-X1) *DX/L+(Y-Yl)*DY/L

The calculated distance value, D, is stored in the fifth buffer of the temporary storage buffers 148.
Block 206 then directs the microprocessor 46 to determine whether or not the distance value stored in the fifth buffer of the temporary storage buffers 148 is less than or equal to zero. If the distance is less than or equal to zero, the nearest point on the segment to the point under consideration is the tail point (X1, Y1) of the segment.
The microprocessor 46 is therefore directed to block 208 in which a distance value is calculated according to the following equation:

distance=sqrt((X1-X)A2 + (Yl-Y)A2) If, at block 206, the distance value stored in the fourth temporary register is not less than or equal to zero, block 210 directs the microprocessor 46 to read the distance stored in the fifth temporary buffer of the temporary storage buffers 148 and to read the segment length stored in the third temporary register and determine whether or not the distance value is greater than the segment length value and if so, the nearest point on the segment to the point under consideration is the headpoint (X2, Y2) of the segment. The microprocessor is therefore directed to proceed to block 212 which directs the microprocessor 46 to calculate a distance value according to the relation:

distance=sqrt((X2-X)A2 + (Y2-Y)A2) This distance value is stored in the fourth temporary register.

If at block 210, the distance value is not greater than the segment length value, the point under consideration is considered to lie between the end points of the segment and the perpendicular distance to the segment is calculated.
In this regard, block 214 directs the microprocessor 46 to calculate a distance value according to the following equation:

distance= (Y-Yl) *DX/L + (X-Xl) *DY/L

After calculating a distance value, block 216 directs the microprocessor to store the calculated distance value in a sixth temporary buffer of the temporary storage buffers 148. The microprocessor 46 is then directed to exit the point/segment distance algorithm 106 and return to the closest segment algorithm 104 shown in Figure 8.

Referring back to Figure 8, when the Point/Segment distance algorithm is completed at block 304, block 221 directs the microprocessor 46 to compare the distance calculated by the point segment distance algorithm stored in the sixth temporary buffer of the temporary storage buffers 148, with the contents of a smallest distance register not shown and to store the lesser of the distance calculated by the point segment distance algorithm and the contents of the smallest distance register (not shown), and to store the target line point index value associated with the headpoint of the target line segment associated with the smallest distance value in a smallest index register not shown.

Block 219 then directs the processor to repeat blocks 300, 302, 304 and 221 until each target line segment has been considered. This has the effect of updating the smallest distance register to ultimately contain the smallest distance value of all segments considered and the smallest index register to contain the index or the associated segment.

Block 223 then directs the microprocessor 46 to store the smallest distance value in the second temporary buffer and to store the target line point index value associated with the smallest distance value in the third temporary buffer of the temporary storage buffers 148. The closest segment algorithm 104 is then ended and processing returns to the target line algorithm 100 shown in Figure 7.

Referring back to Figure 7, upon calculating the distance from the vehicle to the target line, and identifying the nearest target line point, block 196 directs the microprocessor 46 to read the maximum deviation distance data stored in the target line parameter list 118, and the data representing the smallest distance stored in the second temporary buffer of the temporary storage buffers 148. If the data representing the smallest distance value is greater than the data representing the maximum deviation 5 distance, the microprocessor 46 is directed to proceed to block 192, which initializes the target pattern as described above. Otherwise, the microprocessor 46 is directed to proceed to block 198 which directs the microprocessor 46 to calculate the distance from the nearest target line point as addressed by the contents of the third temporary buffer of the temporary storage buffers 148 to the point addressed by the target line headpoint index buffer 138 shown in Figure 4b, i.e., the point representing the head of the target line head segment.
This is done by multiplying the segment length stored in the target line parameter list by the number of points in the target line list, between the nearest target line point, i.e., the point representing the head of the target line segment associated with the smallest distance and the point representing the head of the target line.

Block 200 then directs the microprocessor 46 to determine whether or not the distance calculated in block 198 is less than the forward length of target line value stored in the 25 target line parameter list 118. If it is, the vehicle position is considered to be near the headpoint of the target line and block 202 directs the microprocessor 46 to call the target line segment algorithm 108 shown in Figure 10 to generate a new target line segment. Otherwise, the 30 target line algorithm 100 is completed and the microprocessor 46 returns to block 166 of the main algorithm 94 shown in Figure 5. Thus, the processor is programmed to determine which of the target line segments has a headpoint corresponding to a position in space 35 nearest to the spacial position of the vehicle, as compared to the positions in space of headpoints of the remaining target line segments. In addition, the processor is CA 022l2240 l997-08-Ol programmed to determine the coordinates of a new distal point, i.e. target line head segment when the sum of the predefined distances between the point nearest to the spacial position of the vehicle and the distal point is 5 less than a first predefined distance, the first predefined distance corresponding to the forward length of target line value stored in the target line parameter list 118.

Tarqet Line Seqment Alqorithm Fiqure 10 Referring to Figure 10, the target line segment algorithm 108 directs the microprocessor to identify a safety square, and to identify records having bounding rectangle fields bounding areas common to the safety square, and to call the 15 obstacle algorithm to produce a new head segment of the target line, where the head segment does not interfere with obstacles within the safety square.

Fiqure 11 Referring to Figures 10 and 11, upon entry into the target line segment algorithm 108, block 218 directs the microprocessor 46 to read the target line head position 53 from the target line headpoint record stored in the target line point list 126, to read the segment length stored in 25 the target line parameter list 118, and to read the maximum working device width stored in the initial vehicle parameter list 114. Block 224 directs the microprocessor 46 to call the bounding rectangle algorithm shown in Figures 14a and 14b.

Boundinq Rectanqle Alqorithm Fiqures 14a and 14b Referring to Figure 14a, Block 293 directs the processor to write data representing an active state into a last 35 inputted segment flag buffer (not shown). Block 262 then directs the processor to address the mapping data list 122 to locate a first record having an attribute field having a barrier flag set to active. Upon finding such a record, block 263 then directs the microprocessor 46 to calculate a safety width by adding the safety distance to the target line segment length stored in the target line parameter 5 list and one-half of the maximum working device width stored in the maximum working device width buffer 130. The result is stored as the safety width, in the first temporary buffer of the temporary storage buffers 148.

Referring to Figures 11 and 14a, Block 267 then directs the microprocessor 46 to determine and store in temporary registers Xmin, Xmax and Ymin, YmaX coordinates 252, 254, 256 and 258 of a safety square 259 centred at the distal point or target line head position 53 and having sides of length 15 equal to twice the safety width. Thus, the processor is programmed to compute the coordinates of a safety square having a centre coincident with the distal point and sides having a length of a-t least twice the first predefined distance.
Block 264 then directs the processor to load the bounding rectangle values of the record under consideration into further temporary registers (not shown).

25 Block 266 directs the processor to compare the safety square maximum X,max, Y1maX and minimum (X,min, Y,min) coordinates to the maximum (X2max and Y2maX) and minimum coordinates of the bounding rectangle of the record under (X2max Y2max) consideration. If either of the maximum safety square X1max 30 and YlmaX coordinates is less than the respective values representing the minimum X2min and Y2min or if either value representing the minimum safety square X,min and Y,min coordinate is greater than the respective values representing the maximum X2max and Y2maX of the bounding 35 rectangle, the landmark associated with the record under consideration is considered to be out of the range of the safety square and is ignored, whereupon the processor is CA 022l2240 l997-08-Ol directed to block 278. Otherwise, the processor is directed to block 268 of Figure 14b. Thus, the processor is programmed to compare coordinates of the bounding rectangle of the object with the coordinates of the safety square to determine whether or not any portion of the object is within the safety square.

Referring to Figure 14a, Block 278 directs the processor to determine whether or not all records in the mapping data list 122 have been examined. If all records have been examined the processor is directed to exit the bounding rectangle algorithm. Otherwise, the processor is directed back to block 262 to examine the next record.

Referring to Figure 14b, at block 268 the processor is directed to retrieve a pair of points from the position data field 93 of the record under consideration. The pair of points represent a line segment head and tail of a line segment associated with the landmark or work swath associated with the record under consideration. Block 270 then directs the processor to load the identified line segment head and tail points into temporary registers (not shown).

Block 272 then directs the processor to determine whether or not either point of the identified line segment is contained within the safety square, by comparing the head and the tail points of the line segment to the minimum and maximum X and Y coordinates of the safety square. If at block 272, either point of the identified line segment is contained within the safety square, block 283 directs the processor to write data representing an inactive state into the last inputted segment flag buffer and the processor is directed to block 276. Otherwise, if neither of the points identifying the line segment is contained within the safety square, the processor is directed to block 287 which directs the processor to determine whether or not the last CA 022l2240 l997-08-Ol inputted segment flag buffer contains data representing an inactive state. If the data represents an active state the processor is directed to block 276. If the data represents an inactive state, the processor is directed to block 274 which directs the microprocessor 46 to place the coordinates of the line segment under consideration and the safety distance associated with the segment under consideration in an obstacle record and to append this obstacle record to the obstacle list 140 shown in Figure 4c. Thus, the processor is programmed to, for objects having bounding rectangle coordinates within the safety square, determine pairs of coordinates of successive points, representing heads and tails respectively of respective obstacle line segments approximating the surface 15 of the object, and determine whether or not either of the pairs of coordinates representing an obstacle line segment is within the safety square, the safety square representing at least a portion of the space. In addition, the processor is programmed to place the coordinates of 20 obstacle line segments having at least one coordinate within the safety square in respective obstacle records and append the obstacle records to an obstacle list. If the line segment is associated with initial mapping data, the safety distance is obtained from the associated attribute 25 field whereas if the line segment is associated with completed work, the safety distance is obtained from the vehicle parameter list. Thus, line segments of the work swath are treated as obstacle line segments. Block 276 directs the processor to consider whether or not all line segments identified by the points stored in the record under consideration have been considered and, if so, the processor is directed to proceed to block 278 of Figure 14a and continue processing.

Otherwise, the processor is directed to return to block 268 whereupon the next segment associated with the record under consideration is considered. Thus, the bounding rectangle CA 022l2240 l997-08-Ol algorithm acts to direct the processor to append to the obstacle list 140 a plurality of pairs of points which identify segments of landmarks, which lie within the bounding rectangle and which are to be considered obstacles 5 or barriers to the vehicle. It also directs the processor to store with each landmark the safety distance associated with the landmark.

Upon completion of the bounding rectangle algorithm after block 278 thereof, the processor is directed back to the block 227 of the target line segment algorithm 108 shown in Figure 10.

Referring back to Figure 10, block 227 of the target line 15 segment algorithm 108 directs the processor to read the obstacle list to determine whether or not the obstacle list includes any records. If not, then block 229 directs the processor to calculate a new target line head position according to the relations:

X~ew = segment length * Cos (heading) + X
Ynew = segment length * Sin (heading) + Y1 2 5 where X1, Y1 represent the headpoint of the target line head segment;
heading is the heading value stored in the buffer target line heading buffer;
Xnew, Ynew is the new target line headpoint Thus, the processor is directed to determine the coordinates of a first point in space disposed at a second predefined distance from the spacial position, where the 40 second predefined distance is the segment length. Each time the target line algorithm is run, the processor effectively determines the coordinates of a successive point in space spaced apart from the first point by the second predefined distance, the successive point representing a target line ray.

The new target line head position Xnew, YneW is then stored in the target line record and the target line point index buffer 139 is updated to contain the location of the new target line head position. A new target line head segment has thus just been added to the target line list.

If the obstacle list 140 is not empty, block 228 of the target line segment algorithm 108 then directs the microprocessor to call the obstacle algorithm 110 shown in Figure 12, which directs the microprocessor 46 to determine whether or not an obstacle is located within user-defined observation angles on opposite sides of the target line heading.

Obstacle alqorithm Fiqure 12 Referring to Figure 12, the obstacle algorithm 10 directs the microprocessor to produce a plurality of possible target line head segments, that is, possible distal target line segments most distal to the current position, or view point of the vehicle. The possible target line head segments are produced at various angles to the current target line heading and then segments which cross a line segment of an obstacle or which extend beyond a predetermined distance to a line segment of an obstacle are eliminated, leaving only possible target line segments which do not interfere with nearby obstacles. Of these possible target line segments, the target line segment having a headpoint disposed at the least distance from the nearest line segment of the nearest obstacle is selected as the new target line segment.
Referring to Figures 11 and 12, the obstacle algorithm begins with block 230 which directs the microprocessor to CA 022l2240 l997-08-Ol retrieve the heading of the target line from the target line heading buffer 119.

Block 232 then directs the microprocessor 46 to calculate 5 possible rays from the headpoint of the target line head segment identified by the target line headpoint index buffer 138 by reading the segment length, the number of rays, ray spacing, and the initial observation angle from the target line parameter list 118.
In this embodiment, the initial observation angle is 60 degrees and, therefore, has boundaries 288 and 290 between which the possible rays are calculated. In this embodiment, the number of rays is five and, therefore, the 15 angular spacing value is 15 degrees. The rays thus extend at multiples of 15 degrees on opposite sides of the heading and, directly on the heading. Thus, the processor is programmed to produce a list of points such that the headpoints identify headpoints of target line rays at 20 multiples of a predefined angle to the current heading of the distal target line segment.

Distal end points of respective rays 280, 281, 282, 284, 285 are calculated according to the following relations:

For N = 1 to Number of Rays X~w =segment_length* cos(heading angle + Na) + X
Y~w =segment_length* sin(heading angle + Na) + Yl where Xnew, YneW is end point of ray, segment 3 5 length is a value obtained from the target line buffer, heading angle is the smoothed heading value stored in the smoothed heading buffer 136, N is an integer between 0 and 2 and Xl, Y1 is the current headpoint of the target line.
(a) is the angular spacing value Each of the rays has a common tail point, namely the end point (Xl, Y1) of the target line head segment.

Using the end points of respective rays and the common tail point, the microprocessor stores a plurality of sets of number pairs in the target ray list 146 shown in Figure 4e, where each set corresponds to a distal end point of a respective ray. Thus, the processor is programmed to produce a target ray list of points representing respective headpoints of target line rays representing possible distal target line segments, each of the points including an x coordinate and a y coordinate.

Block 231 then directs the microprocessor to write data representing an active state into a first obstacle flag buffer (not shown).

Block 233 then directs the processor to retrieve a ray point from the target ray list and to clear the first temporary buffer of the temporary storage buffers 148. The ray retrieved from the target ray list is addressed by the contents of the ray index buffer 147 and, at this point in the algorithm, the first ray line point record 145 is addressed.
Block 235 then directs the processor to set the obstacle list index to address the first obstacle record. Block 237 then directs the processor to call the segment crossing algorithm shown in Figure 13.

Seqment Crossinq Alqorithm Fiqure 13 Referring to Figure 13, the segment crossing algorithm 112 directs the microprocessor to use linear algebra principles to find an intersection point of a line identified by the end points of a segment under consideration and a line identified by the end points of a target line segment. If the intersection point is within the limits of the coordinates of the points identifying each line, the segments are considered to cross and the segment under consideration is eliminated from consideration.

Referring to Figures 11 and 13, if the ray under consideration is ray 285 and the landmark line segment under consideration is segment 275, block 246 directs the microprocessor to produce linear equations representing the ray 284 and the object line segment 275 respectively, by applying conventional mathematical methods to respective end points of ray 284 as obtained from the target ray list 146 in Figure 4e and the object line segment 275 as determined from the obstacle list 140 shown in Figure 4c.
After producing such equations, the equations are solved using linear algebra, to obtain a solution which is a pair of coordinates representing an intersection point 291 of the lines represented by the equations, if an intersection point exists.

Block 248 of the segment crossing algorithm then directs the microprocessor 46 to determine whether or not the intersection point 291 is between the coordinates of the ray line and the object line respective segment, by determining whether or not the X-coordinate of the solution is between both X-coordinates of the ray 285 and both X-coordinates of the object line segment 275 and by determining whether or not the Y-coordinate of the solution is between both Y-coordinates of the ray 285 and both Y-coordinates of the object line segment 275. Thus, the processor is programmed to determine whether or not a target line ray crosses the obstacle line segment by producing linear equations representing the target line ray and the obstacle line segment, and by solving the linear equations to determine a point of intersection of the target line ray and the obstacle line segment, and by determining whether or not the point of intersection is within respective X coordinates and respective Y
coordinates of the points identifying the target line ray and the obstacle line segment. If the X and Y-coordinates of the solution are within the indicated bounds, the ray and object line segments are considered to cross and block 250 directs the microprocessor to remove the number pairs representing the ray under consideration from the target ray list 146 to eliminate the ray from further consideration and directs the processor to write data representing an active state into a ray eliminated flag buffer (not shown). Thus, in Figure 11, the number pair corresponding to ray 285 is eliminated from the target ray list 146. Thus, the processor is programmed to eliminate from the target ray list of points, headpoints identifying target line rays which cross an obstacle line segment identified by coordinates stored in the obstacle list. In other words, the processor is programmed to eliminate from the plurality of possible target line segments target line segments which cross obstacle line segments within the second pre-defined distance of the current position point.

If either the X or Y-coordinate of the solution is not within the indicated bounds such as in the case of rays 280, 281, 282, 284 with respect to object line segment 275, these rays and segment are considered not to cross and the number pairs representing these rays are left intact in the target ray list 146 for further consideration. The number pairs associated with rays 280, 281, 282 and 284 are therefore left intact in the target ray list 146 and the segment crossing algorithm is ended. Effectively, the segment crossing algorithm and the obstacle algorithm code direct the processor to compare each target line segment with obstacle line segments within the second pre-defined distance of the current position point to determine whether any target line segment crosses an obstacle line segment.

Upon completion of the segment crossing algorithm 112, the processor is directed back to block 239 of the obstacle algorithm shown in Figure 12a, block 239 directs the processor to read the ray elimination flag to determine whether or not a ray has been eliminated. If so, block 241 directs the processor to increment the ray index and proceed back to block 233 where the next ray in the target ray list 146 is addressed.
If at block 239, the microprocessor finds that the ray elimination flag has not been set, block 243 directs the processor to calculate the distance between the end point of the ray, as specified by the contents of the ray line point record 145, and the segment under consideration.
Block 243 directs the microprocessor to pass the two points identifying the current obstacle segment under consideration and the end point of the current ray under consideration to the point/segment distance algorithm 106 shown in Figure 9. As described above, the point/segment distance algorithm 106 returns a distance value. Block 245 then directs the processor to compare this distance value against the sum of the safety distance attributed to the obstacle segment associated with the object and one-half of the current boom width stored in the working device width buffer, to determine whether or not the distance value is less than this sum. If so, then block 247 directs the processor to remove the number pair associated with the current ray under consideration from the target ray list 146 to eliminate the ray from further consideration. The processor is then directed to block 241 which directs the processor to increment the ray index to point to the next ray in the target ray list. If at block 245, the distance value is not less than the sum indicated then the number pair associated with the current ray under consideration is left intact in the target ray list 146. Thus, the processor is programmed to eliminate from the target ray list, headpoints identifying target line rays having headpoints which are disposed nearer than a second predefined distance to an obstacle line segment identified by coordinates stored in the obstacle list. In other words, the processor is programmed to eliminate from the plurality of possible target line segments, each target line segment having a headpoint no nearer than the safety distance to the object. In the example shown in Figure 11, rays 281, 282 and 284 have endpoints too close to the object, therefore, the number pairs associated with rays 281, 282 and 284 are removed from the target ray list 146 leaving only the number of pairs associated with ray 280.
Thus, the processor is programmed to determine whether or not the target line ray crosses any of the obstacle line segments and whether or not the end point of the target line ray, is within a second predefined distance of any of the obstacle line segments where the second predefined distance is the sum of the safety distance attributed to the obstacle segment associated with the object and one-half of the current boom width stored in the working devicewidth buffer 130.

Referring to Figure 12b, block 249 then directs the processor to read the first obstacle flag buffer to determine whether or not this is the first obstacle segment considered. If so, block 251 directs the processor to store the distance calculated in block 243 in the first temporary buffer of the temporary storage buffers 148 and to set the first obstacle flag to inactive.
If at block 249, the obstacle segment under consideration is not related to the first obstacle, i.e., the first obstacle flag is not set, block 253 directs the processor to determine whether the distance calculated in block 243 is less than the distance value stored in the first temporary buffer. If so, then the current distance is transferred to the first temporary buffer. If not, then block 255 directs the processor to review the current obstacle record to determine whether or not all line segments have been considered by the algorithm. If not, then the processor is then directed to block 238 which directs the processor to increment the obstacle list index to point to the next record in the obstacle list. The processor is then returned to block 235 of Figure 12a, where the next segment identified by the currently addressed obstacle list record is retrieved and considered in the algorithm as described above.

Referring back to Figure 12b, if at block 255 all segments have been considered, block 257 directs the processor to determine whether or not the ray under consideration is the first ray to be addressed by this portion of the algorithm.
If so, then block 260 directs the processor to transfer the distance value stored in the first temporary buffer to the second temporary buffer of the temporary storage buffers 148 and to store the current ray index value in the third temporary buffer of the temporary storage buffers 148.

If at block 257, the ray under consideration is not the first ray to be addressed by this part of the algorithm, block 261 directs the processor to determine whether or not the distance stored in the first temporary buffer is less than the distance stored in the second temporary buffer and if so, to proceed to block 260 to transfer the contents of the first temporary buffer into the second temporary buffer and to store the current ray index in the third temporary buffer. After completion of block 260 or if the distance contained in the first temporary buffer is not less than the distance contained in the second temporary buffer, block 265 of Figure 12c directs the processor to determine whether or not all rays left in the target line list have been considered. If not, then block 241 directs the processor to increment the ray index and the processor is 5 directed back to block 233 to retrieve the next ray in the target ray list.

If at block 265, all rays have been considered, block 269 directs the processor to determine whether or not the third temporary buffer has any contents, i.e., is undefined.
This would be the case where there are no rays left in the target ray list. If the contents of the third temporary buffer are defined, then block 279 directs the processor to select as the new target segment, the ray identified by the 15 contents of the third temporary buffer, as this ray is disposed at the least distance from an obstacle line segment. The processor is then returned back to the target line segment algorithm, shown in Figure 10. Thus, the processor is programmed to select as the distal target line 20 segment, a target line ray having a headpoint disposed at the least distance from an obstacle line segment.
Otherwise, at block 269 if the contents of the third temporary buffer are undefined, block 271 directs the processor to calculate two extra rays extending at plus and 25 minus 5 degrees respectively from respective boundaries 288 and 290 of the observation angle. As, in this embodiment, the initial observation angle stored in the target line parameter list 118, is 60 degrees, the two extra rays adjacent the first observation angle boundary would extend at 35 and -35 degrees respectively relative to the target line heading. The extra rays so calculated are stored in the target ray list.

Each time the processor encounters block 269, if no ray points are stored in the target ray list 146, block 271 directs the processor to calculate two new rays at a further 5 degree increment from the initial observation angle boundaries. Block 273 then directs the processor to determine whether or not the new rays calculated extend at angles greater than the additional observation angle limit stored in the target line parameter list. If the newly calculated rays extend relative to the initial observation angle boundaries at angles greater than the additional observation angle limit, the algorithm is ended and the processor terminates generation of the target line.

If at block 273, extra rays have been generated and have been placed in the target ray list, block 277 directs the processor to calculate the heading for the extra rays and clears the first temporary buffer. The processor is then directed back to block 235 where subsequent portions of the algorithm are repeated.

The effect of block 271 and 273 is that new rays are produced at + 5 degrees, + 10 degrees, + 15 degrees, etc., from the initial observation boundaries until at least one ray is produced which allows the processor to reach block 269 with a ray point in the target ray list 146 or until the new rays calculated extend at an angle which exceeds the additional observation angle stored in the target line parameter list 118. In other words, the processor is programmed to determine whether or not the target ray list 146 is empty and if so, produce new target line rays having angles which are multiples of a pre-defined angle from boundaries of the initial observation angle until the target ray list 146 includes at least one headpoint identifying a target line ray which does not cross an obstacle line segment and which is not nearer than the second predefined distance to the obstacle line segment.

The effect of the obstacle algorithm is to store in the third temporary buffer of the temporary storage buffers 148, the ray index of a ray identified in the target ray list, such ray being the ray which will become the most distal target line segment. Thus, in effect, the processor is programmed to determine the coordinates of a successive point in space spaced apart from the first point by the second pre-defined distance, the successive point representing a target line ray. In other words, the processor is programmed to select coordinates identifying a target line segment nearest at least one obstacle line segment of the object as those which identify a target line head segment.
As the target line point list is only capable of storing a finite number of number pairs, each time a new target line head segment is added, a target line tail segment is deleted from the target line print list. Thus, the processor is programmed to delete the coordinates of a target line tail segment of the target line when the coordinates of a new target line head segment are determined to maintain a target line having a pre-defined length.
At any time, the processor may receive and store new mapping data in the mapping data list. This new mapping data is thus taken into account each time a new target line head segment is calculated. Thus, the processor is programmed to receive and store new mapping data after at least one point position is computed such that the calculation of subsequent point positions is performed using the initial mapping data and the new mapping data.

The algorithms implemented by code stored in the ROM, except the code for implementing the visible square algorithm, provide direction to the processor to compute point positions of a plurality of respective target line segments, relative to the first and second spacial positions, to produce a representation of a target line extending from at least one of the first and second spacial positions, the point positions being computed such that the target line segments associated with respective point positions do not extend between the points representing the contour of any object represented by the mapping data stored in the memory at the time at least one point position is computed, such that each of the point positions is computed using mapping data available at the time at which the point positions are calculated.

Visible Square Alqorithm Referring to Figure 15, the visible square algorithm 116 is called by block 166 of the main algorithm shown in Figure 5. Generally, the visible square algorithm acts to send to the display interface, information regarding landmarks and the target line which are with the field of view determined by the perspective view parameter list 120. The particular items to be viewed in the perspective display are determined according to the visible square algorithm shown in Figure 15, which determines which records of the user-inputted landmark list (124), completed work list (128) and mapping data list (122), have points located within the portion of the work area to be viewed and which forwards such points in OpenGL commands to the display interface.
This acts as a filtering procedure for filtering points to be sent to the display such that only those points within the required viewing area are sent to the display. This has the effect of relieving the display interface of the task of filtering, thereby more rapidly producing an updated perspective view.

Block 292 directs the microprocessor 46 to set variables Xlmax, X1min, YlmaX and Ylmin to variables representing the coordinates of the area to be viewed. These variables are determined from the present position of the vehicle (smoothed position buffer) and the parameters stored in the perspective view parameter list 120, and represent the viewing coordinates of the area to be depicted on the display.

CA 022l2240 l997-08-Ol Block 294 then directs the microprocessor 46 to retrieve a record from the mapping data list 122, the target line point list 126, the user-inputted landmarks list 124, or the completed work list 128. When a record is retrieved 5 from the completed work list, the processor calculates a swath width from the vehicle position stored in the completed work record and the contents of the working device width buffer 130. Effectively, two points are produced, on opposite sides of the vehicle position, at right angles to the direction of travel, or vehicle heading. The processor is thus programmed to compute, from the position points of the vehicle, position points traversed by a working device transported by the vehicle in the space.

Block 296 then directs the processor 46 to determine the minimum and maximum X values and the minimum and maximum Y
values in the record and to assign these values to variables X2min, X2max, Y2min, Y2maX respectively. This has the 20 effect of assigning the ranges of points within the record.

Block 298 then directs the processor to determine whether the maximum X point in the record is less than the minimum X viewing coordinate, or the minimum X point of the record 25 iS greater than the maximum X viewing coordinate, or the maximum Y point in the record is less than the minimum Y
point of the viewing coordinates, or the minimum Y point of the record is greater than the maximum Y viewing coordinate, and if so, to direct the processor to block 303 which directs the processor back to block 294. Otherwise, the processor is directed to block 301. Effectively, block 298 directs the processor to determine whether or not any landmarks indicated by the record under consideration lie outside the viewing coordinates and if so, to ignore such 3 5 landmarks.

Block 301 is reached when all points contained in the record under consideration lie within the viewing area.
This block directs the processor to send a display command, in the OpenGL language, to the display interface 56. The display interface further performs its own filtering of points to create the display. The display command includes a view point or point from which the perspective view is seen which is computed relative to a special position of the vehicle. Thus the processor is programmed to produce commands recognizable by the display for causing the display to produce a visual representation of the space, as seen from the viewpoint in the direction of the heading, the visual representation including a representation of the object derived from the coordinates of various points on the surface of the object.

The display command further includes instructions to display at least one target line segment extending at the heading between the view point and the headpoint. Thus, the processor is programmed to identify the coordinates of an area representing a sub-portion of the space and to send to the display commands including the coordinates of objects in the mapping data list, where the coordinates identify points within the area, such that representations of the objects are displayed in the perspective view.
Thus, the processor is programmed to divide the initial mapping data and the new mapping data into sub-portions of coordinates of points representing the surface contour of objects, where the surface contours are within a corresponding sub-portion of the space.

The display shown at 58 in Figure 3 thus acts as a display for displaying a visual representation of at least a portion of the space, in response to the target line display command, the visual representation including the viewpoint, the headpoint and the target line segment extending at the first heading between the viewpoint and the headpoint. The visual representation is effectively a virtual reality representation of the space and is seen as perspective view of the space, the perspective view including the viewpoint, the headpoint and the target line.
5 The target line acts as a prediction of the path of the vehicle in view of obstacles which may be in the path of the vehicle. The path is predicted on the basis of information available at the instant a new target line segment point position is calculated. Thus, the target line is dynamically generated.

It may also be said that the processor is programmed to produce commands to the display for the display to display in the perspective view, representations of the successive points in space and a target line having segments extending between respective pairs of the representations of successive points in space, the target line segments including a distal target line segment most distal to the viewpoint, the distal target line segment having a current heading.

It will be appreciated that blocks 294, 296, 298 and 303 form a loop which has the effect of directing the processor to examine each record in each list to determine whether or not it should be used in the display of the area viewed by the operator, and if so, to cause an appropriate display command to be sent to the display interface 56.

Alternatives Alternatively, the GPS receiver may be replaced with a GPS
receiver having a VHF receiver for receiving differential GPS signals used to correct the signal produced by conventional GPS to overcome selective tuning to produce more accurate position signals.

CA 022l2240 l997-08-Ol In effect, the apparatus and method according to the invention provide a way of guiding a vehicle or even a hand-held receiver by predicting a path the vehicle or receiver is to take on the basis of obstacle information 5 which may be previously stored and which may be gathered during operation of the apparatus. The invention contemplates including a worked area as obstacle information, which allows the path of the vehicle to be predicted with the knowledge of where the vehicle has been, allowing the path to be predicted in such a manner that the vehicle avoids areas already traversed. This has applications in spraying crops, for example, where the vehicle operator can be guided to avoid spraying areas already sprayed, without the need for markers and the like 15 which are subject to weather conditions for visibility.

While specific embodiments of the invention have been described and illustrated, such embodiments should be considered illustrative of the invention only and not as limiting the invention as construed in accordance with the accompanying claims.

Claims (68)

1. A method of displaying a representation of an area in a space, the method including the steps of:

a) receiving mapping data representing coordinates of various points on a surface of at least one object in said space and storing said coordinates in memory;

b) receiving position signals indicative of at least first and second spacial positions of a receiver operable to move and to receive said position signals in said space;

c) computing a heading of said receiver from said position signals;

d) computing a viewpoint relative to at least one of said first and second spacial positions; and e) producing a visual representation of said space, as seen from said viewpoint in the direction of said heading, said visual representation including a representation of said object derived from said coordinates of various points on said surface of said object.

2. A method as claimed in claim 1 further including the step of producing a virtual reality representation of said space, as seen from said viewpoint in the direction of said heading, said virtual reality representation including a representation of said at least one object derived from said coordinates of various points on said surface of said at least one object.

3. A method as claimed in claim 2 further including the step of simultaneously producing said virtual reality representation and a plan view of said space.

4. A method as claimed in claim 3 further including the step of receiving mapping data representing the coordinates of various points on respective surfaces of a plurality of objects in said space, storing said coordinates in memory and producing respective representations of each of said objects in said visual representation such that the user can view said respective representations simultaneously.

5. A method as claimed in claim 4 further including the steps of:

a) identifying coordinates of an area representing at least a portion of said space;

b) identifying objects within said area; and, c) sending to a display interface said coordinates of surfaces of objects within said area.

6. A method as claimed in claim 1 further including the step of computing point positions of a plurality of respective target line segments, relative to said first and second spacial positions, to produce a representation of a target line extending at a first pre-defined distance from at least one of said first and second spacial positions, said point positions being computed such that said target line segments associated with respective point positions do not extend between said points on said surface of said at least one object.

7. A method as claimed in claim 6 further including the step of computing said point positions such that said point positions are no nearer than a safety distance to said at least one object.

8. A method as claimed in claim 7 further including the step of computing said point positions such that said target line generally follows the contour of said at least one object.

9. A method as claimed in claim 6 further including the step of producing a visual representation of said target line.

10. A method as claimed in claim 1 further including the step of updating said visual representation as said receiver moves in said space.

11. A method of guidance in a space, the method comprising the steps of:

a) receiving and storing in memory mapping data representing the coordinates of various points identifying a surface contour of at least one object in said space;

b) receiving position signals indicative of at least first and second spacial positions of a receiver operable to move in a path in said space, and operable to receive said position signals;

c) computing point positions of a plurality of respective target line segments, relative to said first and second spacial positions, to produce a representation of a target line extending from at least one of said first and second spacial positions, said point positions being computed such that said target line segments associated with respective point positions do not extend between said points representing the contour of any object represented by said mapping data stored in said memory at the time at least one point position is computed, such that each of the point positions is computed using mapping data available at the time at which said point positions are calculated; and d) producing a signal representing a prediction of the path of said receiver as indicated by said point positions.

12. A method as claimed in claim 11 further including the step of receiving and storing new mapping data after at least one point position is computed such that the calculation of subsequent point positions is performed using said initial mapping data and said new mapping data.

13. A method as claimed in claim 12 further including the step of accumulating, in a completed work record, position points of said receiver, said position points representing positions which said receiver has traversed.

14. A method as claimed in claim 13 further including the step of accumulating a pre-defined number of position points in said completed work record and storing said completed work record in a completed work list when said completed work record contains said pre-defined number of position points and including said completed work list in said new mapping data.

15. A method as claimed in claim 14 further including the step of dividing said initial mapping data and said new mapping data into sub-portions of coordinates of points representing the contours of surfaces of objects, where said surfaces of said objects are within a corresponding sub-portion of said space.

16. A method as claimed in claim 11 further including the step of computing said point positions such that said point positions are no nearer than said safety distance to said at least one object.

17. A method as claimed in claim 16 further including the step of computing the position of a viewpoint relative to at least one of said first and second spacial positions.

18. A method as claimed in claim 17 further including the step of computing from said position signals, a heading of said receiver.

19. A method as claimed in claim 17 further including the step of producing a visual representation of said target line.

20. A method as claimed in claim 19 wherein said visual representation includes a virtual reality representation of said space, as seen from said viewpoint in the direction of said heading, said virtual reality representation including said representation of said target line.

21. A method as claimed in claim 20 wherein said virtual reality representation includes a representation of at least one object derived from said coordinates of said various points representing the contour of said surface of said at least one object.

22. A method as claimed in claim 21 further including the step of simultaneously producing said virtual reality view and a plan view of said target line.

23. A method as claimed in claim 11 further including the step of updating said prediction as said receiver moves in said space.

24. A method as claimed in claim 11 further including the step of computing said point positions such that said target line generally follows the contour of said at least one object.

25. A method as claimed in claim 11 further including the step of receiving and storing in a mapping data list a plurality of pairs of coordinates identifying said surface of an object within said space, said pairs of coordinates representing heads and tails respectively of obstacle line segments approximating said surface.

26. A method as claimed in claim 25 further including the steps of:

a) identifying coordinates of an area representing at least a portion of said space; and b) identifying pairs of coordinates in said mapping data list which are associated with objects within said area.

27. A method as claimed in claim 26 further including the step of, of said objects identified as being within said area, identifying coordinates of obstacles within a second pre-defined distance of a current point position.

28. A method as claimed in claim 27 further including the step of computing said point positions such that said target line segments associated with respective point positions do not cross obstacle line segments within said second pre-defined distance of said current position point.

29. A method as claimed in claim 28 further including the steps of:

a) computing coordinates of a plurality of possible target line segments;

b) comparing each target line segment with obstacle line segments within said second pre-defined distance of said current position point to determine whether any target line segment crosses an obstacle line segment; and c) eliminating from said plurality of possible target line segments target line segments which cross obstacle line segments within said second pre-defined distance of said current position point.

30. A method as claimed in claim 29 further including the step of eliminating from said plurality of possible target line segments, each target line segment having a headpoint no nearer than said safety distance to said at least one object.

31. A method as claimed in claim 30 further including the step of selecting coordinates identifying a target line segment nearest at least one obstacle line segment of said object as those which identify a target line head segment.

32. A method as claimed in claim 11 further including the step of determining which of said target line segments has a head point corresponding to a position in space nearest to at least one of said first and second spacial positions of said receiver, as compared to the positions in space of headpoints of remaining target line segments.

33. A method as claimed in claim 32 further including the step of determining coordinates of a new target line head segment when the distance between said point nearest to the spacial position of the receiver and said distal point is less than said first pre-defined distance.

34. A method as claimed in claim 33 further including the step of deleting the coordinates of a target line tail segment of said target line when the coordinates of a new target line head segment are determined to maintain a target line having a pre-defined length.

35. An apparatus for displaying a representation of an area in a space, the apparatus comprising:

a) a mapping data receiver for receiving mapping data representing the coordinates of various points identifying a surface contour of at least one object in said space;

b) memory for storing said coordinates;

c) a position signal receiver operable to move in a path in said space, for receiving position signals indicative of at least first and second spacial positions of said position signal receiver;

d) a display; and, e) a processor in communication with said mapping data receiver, said memory, said position signal receiver, and said display, said processor being programmed to:

i) compute a heading of said receiver from said position signals;

ii) compute a viewpoint relative to at least one of said first and second spacial positions;
and iii) produce commands recognizable by said display for causing said display to produce a visual representation of said space, as seen from said viewpoint in the direction of said heading, said visual representation including a representation of said object derived from said coordinates of various points on said surface of said object.

36. An apparatus as claimed in claim 35 wherein said processor is programmed to produce a virtual reality representation of said space, as seen from said viewpoint in the direction of said heading, said virtual reality representation including a representation of said at least one object derived from said coordinates of various points on said surface of said at least one object.

37. An apparatus as claimed in claim 36 wherein said processor is programmed to simultaneously produce said virtual reality representation and a plan view of said space.

38. An apparatus as claimed in claim 37 wherein said processor is programmed to:

a) receive mapping data representing the coordinates of various points on respective surfaces of a plurality of objects in said space;

b) store said coordinates in memory; and c) produce respective representations of each of said objects in said visual representation such that the user can view said respective representations simultaneously.

39. An apparatus as claimed in claim 38 wherein said processor is programmed to:

a) identify coordinates of an area representing at least a portion of said space;

b) identify objects within said area; and, c) send to said display commands including said coordinates of surfaces of objects within said area.

40. An apparatus as claimed in claim 35 wherein said processor is programmed to compute point positions of a plurality of respective target line segments, relative to said first and second spacial positions, to produce a representation of a target line extending at a first pre-defined distance from at least one of said first and second spacial positions, said point positions being computed such that said target line segments associated with respective point positions do not extend between said points on said surface of said at least one object.

41. An apparatus as claimed in claim 40 wherein said processor is programmed to compute said point positions such that said point positions are no nearer than a safety distance to said at least one object.

42. An apparatus as claimed in claim 41 wherein said processor is programmed to compute said point positions such that said target line generally follows the contour of said at least one object.

43. An apparatus as claimed in claim 40 wherein said processor is programmed to produce a visual representation of said target line.

44. An apparatus as claimed in claim 35 wherein said processor is programmed to update said visual representation as said receiver moves in said space.

45. A guidance apparatus comprising:

a) a mapping data receiver for receiving mapping data representing the coordinates of various points identifying a surface contour of at least one object in said space;

b) memory for storing said coordinates;

c) a position signal receiver operable to move in a path in said space, for receiving position signals indicative of at least first and second spacial positions of said position signal receiver;

d) a processor in communication with said mapping data receiver, said memory, and said position signal receiver and programmed to:

i) compute point positions of a plurality of respective target line segments, relative to said first and second spacial positions, to produce a representation of a target line extending from at least one of said first and second spacial positions, said point positions being computed such that said target line segments associated with respective point positions do not extend between said points representing the contour of any object represented by said mapping data stored in said memory at the time at least one point position is computed, such that each of the point positions is computed using mapping data available at the time at which said point positions are calculated;
and ii) produce a signal representing a prediction of the path of said receiver as indicated by said point positions.

46. An apparatus as claimed in claim 45 wherein said processor is programmed to receive and store new mapping data after at least one point position is computed such that the calculation of subsequent point positions is performed using said initial mapping data and said new mapping data.

47. An apparatus as claimed in claim 46 wherein said processor is programmed to accumulate, in a completed work record, position points of said receiver, said position points representing positions which said receiver has traversed.

48. An apparatus as claimed in claim 47 wherein said processor is programmed to accumulate a pre-defined number of position points in said completed work record and store said completed work record in a completed work list when said completed work record contains said pre-defined number of position points and to include said completed work list in said new mapping data.

49. An apparatus as claimed in claim 48 wherein said processor is programmed to divide said initial mapping data and said new mapping data into sub-portions of coordinates of points representing the contours of surfaces of objects, where said surfaces of said objects are within a corresponding sub-portion of said space.

50. An apparatus as claimed in claim 45 wherein said processor is programmed to compute said point positions such that said point positions are no nearer than a safety distance to said at least one object.

51. An apparatus as claimed in claim 50 wherein said processor is programmed to compute the position of a viewpoint relative to at least one of said first and second spacial positions.

52. An apparatus as claimed in claim 51 wherein said processor is programmed to compute from said position signals, a heading of said receiver.

53. An apparatus as claimed in claim 51 further including a display and wherein said processor is programmed to produce display commands for causing said display to produce a visual representation of said target line.

54. An apparatus as claimed in claim 53 wherein said visual representation includes a virtual reality representation of said space, as seen from said viewpoint in the direction of said heading, said virtual reality representation including said representation of said target line.

55. An apparatus as claimed in claim 54 wherein said virtual reality representation includes a representation of at least one object derived from said coordinates of said various points representing the contour of said surface of said at least one object.

56. An apparatus as claimed in claim 55 wherein said processor is programmed to simultaneously produce said virtual reality view and a plan view of said target line.

57. An apparatus as claimed in claim 45 wherein said processor is programmed to update said prediction as said receiver moves in said space.

58. An apparatus as claimed in claim 45 wherein said processor is programmed to compute said point positions such that said target line generally follows the contour of said at least one object.

59. An apparatus as claimed in claim 45 wherein said processor is programmed to receive and store in a mapping data list a plurality of pairs of coordinates identifying said surface of an object within said space, said pairs of coordinates representing heads and tails respectively of obstacle line segments approximating said surface.

60. An apparatus as claimed in claim 59 wherein said processor is programmed to:

a) identify coordinates of an area representing at least a portion of said space; and b) identify pairs of coordinates in said mapping data list which are associated with objects within said area.

61. An apparatus as claimed in claim 60 wherein said processor is programmed to identify coordinates of obstacles within said area, within said second pre-defined distance of a current point position.

62. An apparatus as claimed in claim 61 wherein said processor is programmed to compute said point positions such that said target line segments associated with respective point positions do not cross obstacle line segments within said second pre-defined distance of said current position point.

63. An apparatus as claimed in claim 62 wherein said processor is programmed to:

a) compute coordinates of a plurality of possible target line segments;

b) compare each target line segment with obstacle line segments within said second pre-defined distance of said current position point to determine whether any target line segment crosses an obstacle line segment; and c) eliminate from said plurality of possible target line segments target line segments which cross obstacle line segments within said second pre-defined distance of said current position point.

64. An apparatus as claimed in claim 63 wherein said processor is programmed to eliminate from said plurality of possible target line segments, each target line segment having a headpoint no nearer than a said safety distance to said at least one object.

65. An apparatus as claimed in claim 64 wherein said processor is programmed to select coordinates identifying a target line segment nearest at least one obstacle line segment of said object as those which identify a target line head segment.

66. An apparatus as claimed in claim 45 wherein said processor is programmed to determine which of said target line segments has a head point corresponding to a position in space nearest to at least one of said first and second spacial positions of said receiver, as compared to the positions in space of headpoints of remaining target line segments.

67. An apparatus as claimed in claim 66 wherein said processor is programmed to determine coordinates of a new target line head segment when the distance between said point nearest to the spacial position of the receiver and said distal point is less than said first pre-defined distance.

68. An apparatus as claimed in claim 67 wherein said processor is programmed to delete the coordinates of a target line tail segment of said target line when the coordinates of a new target line head segment are determined to maintain a target line having a pre-defined length.