NO792326L - NAVIGATION NAVIGATION SYSTEM. - Google Patents

Description

Navigation system for the sail led.

IN

The present invention relates to a navigation system for. the sailing guide of the type that includes a log, time measuring device and radar system arranged on a vessel. !

The purpose of the invention is to produce a navigation system which, with the help of a computer system, enables accurate navigation of the vessel in narrow waters using very limited information about the conditions surrounding the route the vessel is to cover. In this way, the requirements that must be placed on the computer system in terms of capacity and computer program are very reasonable, which in turn entails considerably lower costs and makes the system attractive also for vessels of smaller size.

The characteristic of the system according to the invention is evident from the paterite requirements.

The invention must be described in more detail in connection with the accompanying drawings, where:

figure 1 shows a block diagram of the system,

figure 2 schematically shows a laid out route for a vessel with charts drawn with dotted lines, and

figure 3 shows a picture screen with a map and fed radar echo.

The block diagram according to Figure 1 comprises a computer system 10 with a built-in time measuring device, to which a gyrocompass 11, a log 12, a radar system 13, a cassette device 14 and a video screen 15 are connected.

From the gyrocompass 11, respectively the log 12, the computer system 10 receives information about the vessel's course, respectively speed, and can from this information about the speed and time successively calculate the vessel's position while traveling with a predetermined route.

In the cassette device 14 there is pre-arranged information about the maps in the immediate vicinity of certain pre-determined and well-separated points along the mentioned route. This information is latently available to the computer system, and as the vessel passes said points on the route, the relevant maps are successively fed into the computer system 10 and displayed on the fcilled screen. 15.

The radar system 13 is arranged to indicate, at the same time as a map is displayed, a plurality, limited number of radar echoes on the map just displayed. Wood suppression of not

desired radar echoes from the radar system, a limitation j is achieved in the requirement for the computer system's program volume, without reducing the precision in the position indication. The limitation of the radar echo is done in conjunction with the program description from available, previously recorded echo position information.

More specifically, the navigation system works as follows. When one of the positions calculated by the computer system 10 corresponds to a certain distance from any of the mentioned points Pn on the route to the nearest subsequent point Pn+1 on the route, the computer system shows the corresponding map to said subsequent point Pn+1, and at the same time the radar system shows the radar echo on the image screen 15. These map images and radar echoes remain on the image screen 15 until its next map image and associated radar echo corresponding to the calculated position for the point Pn+2 on the route is displayed on the screen 15.

The control information determined for the radar system's 13 operation is arranged in advance and available in the computer system. This control information refers to said predetermined and well-separated points P]_, V21P3 P fi Pn+ifpn+2 along the said route, and is arranged to be activated point by point depending on which information about the map images over the route is displayed successively by the computer facility on screen 15.

In the computer system, speed and time are integrated, whereby the distance covered is obtained. This is fed into a comparison circuit, which is also fed with the previously calculated program corresponding to the road task. If there is a match, channels are opened for radar information to the image screen as well as channels for map information from the program.

In Figure 2, the dashed line 20 denotes the ideal path for a vessel, and the solid line 21, respectively 22, the tolerance limits between which the vessel must be navigated so that the risk of grounding does not occur with respect to the land formations 23, 24, 25, 26 and 28. On the Ii route 20, a number of points P-^ Pg are indicated, whereby the distance between these points is dependent on the distance between the tolerance limits 21

and 22. Narrow passages require less distance between points,

see e.g. the distance between points P4|and P5, while open water allows longer distances, see e.g. the distance between the points V± and P2 or Py and Pg. j

To the point P^corresponds to e-; map image limited by the dotted line 27, to the point P2 belongs the map image limited by the dash-dotted line 29. and to the point P7 belongs a map image limited by the longitudinal and transverse line 30. For position determination using the radar system when the vessel is in or near the point P-^, three targets located in the three direction indications 271, 272 and 273 are used. The echo from other goals are thus suppressed. Similarly

for the point V 2 there are three measurements with the directions 291, 292 and 293,

as well as for point P7 three measures with the directions 301, 302 and 303.

In these cases, each of the three consecutive map images will therefore contain three geographical points or rather small circular surfaces, whose center corresponds to the points' (target) exact position (target value), and whose periphery indicates the tolerance limit for where far from the said centre, the corresponding radar echo (er value) must be received so that the vessel can be said to be within specified tolerance limits in the sail direction. In Figure 3, three such circular surfaces, denoted by 31, 32 and 33, are shown on the screen 15.

Incoming radar echoes (crosses) are denoted by 311, 321

and 331. The vessel is marked with an arrow 34 (target value). Crossings 311, 321 and 331 are well within the respective circles, i.e. the vessel is well within the specified tolerance limits, but not on the ideal route line 20, because the crossings are one distance from the center of the respective circles, diagonally to the right. The helmsman can now, guided by the deviation on the screen, change the course somewhat, to compensate for the deviation, and continue to follow the vessel's course.

It is advantageous to implement the system with an indicating means arranged to also emit an audible sound when a radar

echo falls outside a target area shown on the map image.

in

In order to obtain such a "clean" map image as appears in figure 3, it is required that the control information determined for the radar system 13 is arranged in advance and available in the computer system. This control information must relate to the mentioned points P, PQ on the route according to figure 2,

and must be activated point by point according to which the information about the map images over the route is displayed successively by the computer system 10 on the image screen 15. Through this control information j the radar system is brought into operation only during the short moments of time, and at the distances corresponding to the pre-selected targets for each point.

Instead, as used to be common, to show a map of a very large area and let the radar system work

more or less continuously, is shown in this system map-

the images above only the smaller parts that are relevant in connection with the previously determined points. This also requires significantly smaller amounts of information on the cassette which is already recorded on the route the vessel is to take. It is important that there is synchronism between the presentation of the chart images and the passage of the vessel on the particular route. This is provided e.g. through the cassette device 14 being started in connection with the vessel reaching the first point among said predetermined points on the route.

Between the points P^ and P^ in Figure 2, the route shows a course change. It is appropriate to have a special program for the radar system here, so that you e.g. with the help of target 25, you get information about the distance to target 2 5 when you get closer and closer to the course change point, at the same time you also get information about the situation around the vessel during the actual course change, as the radar system is then not locked on e.g. only three goals at once.

As soon as the course change is carried out, the system returns to the previously described map image radar echo principle.

It is appropriate to have as a complement to the now described navigation system a kind of course monitor, with the help of which the helmsman can monitor the course during speed between two immediately following points in the indicated route.

This increases the helmsman's opportunities to keep the vessel on the right course.

Claims (4)

1. Navigation system which includes a log arranged on a vessel, a time measuring device, a radar system and a computer system, characterized in that the computer system (10) is arranged to receive information about the speed, respectively time from the log (12), respectively the time measuring device (i 10) followed by calculation of the vessel's position while underway along a predetermined route, that pre-arranged geographical information about predetermined targets, which constitute map images of the immediate surroundings of certain pre-determined pg well-separated points (P-^, P2 Pg) along the said route (20), are readily available to the computer system (10), and that when a calculated position of the computer system (10) in terms of distance corresponds to the position for it from some of the mentioned points (e.g. Pj_) on the route iji (20) closest subsequent points (P2 ) on the route, the computer system (10) is partly arranged to show the map image belonging to said subsequent point (P2 ) among said arranged map images, partly the radar unit (13) is arranged to simultaneously indicate a plurality of radar echoes from the predetermined targets on the map images, whereby these radar echoes indicated by the radar system (13) can be compared with the predetermined targets' position on the map shown by the computer system (10). 2. Navigation system according to patent claim 1, characterized in that an indicating device is arranged to indicate when a radar echo (321) indicated by the radar system (13) on the map image falls outside a corresponding to said radar echo (321), and by the computer system (10) on the map image displayed target area (32). 3. Navigation system according to claim 1 or 2, characterized in that the control information for the operation of the radar system (13) is arranged in advance and available in the computer system (10), where the control information refers to said predetermined and well-separated points ( P-1,P2 Pg) along the mentioned route (20), and is arranged to activate point by point according to how the map images over the route (20) are successively displayed by the computer system (10). 4. Navi.gas.jons.system According to claim 3, characterized in that the said control information is designed and arranged to enable the position determinations for each one of said p,points (P]_, P2 Pgl' along said route ( 20), and with the use of three predetermined radar targets in connection with travel <p> ective points.