WO2011130861A1

WO2011130861A1 - Object proximity warning system and method

Info

Publication number: WO2011130861A1
Application number: PCT/CH2010/000106
Authority: WO
Inventors: Peter Arnold Stegmaier; Urs Martin Rothacher
Original assignee: Safemine Ag
Priority date: 2010-04-19
Filing date: 2010-04-19
Publication date: 2011-10-27
Also published as: AU2010351500A1; AU2010351500A2; CA2796846C; CA2796846A1; AU2010351500B2

Abstract

A system and a method are disclosed for generating a proximity warning. Based on two different sensing principles proximate objects can be detected by respective monitoring devices (12, 40). The warning system is designed such that each monitoring device (12, 40) issues a warning via a common output device (19).

Description

Object proximity warning system and method

Technical Field

The invention relates to a system and a method for issuing proximity warnings. Background Art

Surface mines and similar sites or areas are generally operated by means of a large number of vehicles, some of which may be exceedingly large and diffi- cult to control and have very limited visibility for the operator .

It has been proposed to use GNSS-devices (GNSS = global navigation satellite system, such as GPS) on board of the vehicles and other objects, such as cranes, to generate proximity warnings in order to reduce the risk of collisions between vehicles. Such a system is e.g. described in WO 2004/047047. The system is based on devices mounted to the objects. Each device comprises a GNSS receiver, a control unit deriving positional data using the signal of the GNSS receiver, a radio circuit for wireless exchange of the positional data with the other devices, and an output device for outputting proximity warnings.

Another approach based on GNNS receivers is disclosed in the International Application No.

PCT/CH2009/000200 incorporated herein by reference.

Other approaches for extra-large vehicles are introduced in "Avoiding accidents with mining vehicles", retrieved and accessed from/on the Internet at

http: //www. flir.com/uploadedFiles/Eurasia/MMC/Appl_Storie s/AS_0020_EN.pdf on February 2, 2010. Accordingly, some of the vehicles are equipped with an 8m radar system which warns the driver when something is in his path. In addition to the radar system GPS traffic alert systems can be installed which warns the driver of any possible accidents .

Disclosure of the Invention

Hence, the problem to be solved by the inven- tion is to provide an improved warning mechanism.

This problem is solved by the system and the method according to the independent claims.

According to a first aspect of the present invention, a system is provided for generating a prox- imity warning. The system comprises a first monitoring device comprising a receiver for a radio based positioning system for determining the position of an object the first monitoring device is mounted to. The system further comprises a second monitoring device - preferably mounted to the same object as the first monitoring device - for measuring the distance to another object, preferably in the vicinity of the present object. A common output device is provided for issuing a first proximity warning in dependence of positional data supplied by the first moni- toring device, and for issuing a second proximity warning in dependence of distance data supplied by the second monitoring device.

Consequently, the common output device is as^¬ signed to both monitoring devices. An "output device" in the context of the present invention is a device for issuing warnings comprising one or more output elements such as visual elements, acoustic elements, or others. Preferably, the output device comprises an interface to a control unit, which processes the outputs of both moni- toring devices thereby triggering the warnings to be issued by the output elements of the output device. Such interface my be at least a unidirectional interface, or may be a bi-directional interface, and may, for example, be implemented as a bus system. The control unit may be arranged remote to the output device or may be integrated into the output device. The control unit itself may com- prise an interface to the two or more monitoring devices which feed their signals into the control unit common to all monitoring devices. Preferably, the control unit may be enabled for evaluating the signals from the multiple monitoring devices in combination. The control unit may be arranged in a common housing with one or more of the output elements. In such scenario, the control unit of the output device receives the signals from the monitor^¬ ing devices directly by means of suitable interfaces. Again, in such a scenario, the control unit may be en- abled for evaluating the signals from the multiple monitoring devices in combination.

By providing a common output device to the monitoring devices, a first step of integrating monitor^¬ ing devices working along different monitoring principles into a single monitoring system is achieved. Irrespective of the signals from the monitoring devices and/or infor^¬ mation in the signals being combined, the output device is embodied as a component in which the output elements are combined. This also holds if the control unit for evaluating the signals from the monitoring devices is em^¬ bodied as part of the output device itself and controls the output elements of the output device.

In a preferred embodiment, the first proximity warning is different to the second proximity warn- ing. This in particular includes that a physical appearance of the first warning differs from a physical appearance of the second warning. Hence, the person in charge is in a position to derive from which kind of monitoring device the warning is basically triggered. For the reason that the two monitoring devices rely on different measuring principles, they inherently provide different kind of information, which may bring the person in charge in a position to better react to potentially dangerous situations. While in an embodiment a GNSS based receiver allows for determining the position of the object the GNSS receiver is mounted to, and, preferably in combination with positional information delivered by GNSS based receivers mounted on other objects, allows for determining the distance to such other objects and preferably the di^¬ rection, it is known that such monitoring device needs to rely on other objects being tagged with a GNSS based re- ceiver, too. This also holds for an embodiment where the current position of the present object determined by means of the GNSS receiver is mapped to a map electronically stored, such map showing possible immobile (or temporarily immobile) obstacles in the vicinity. On the other hand, the second monitoring device may detect proximate objects in a different range, e.g near-by objects, e.g. within the range of 10 meters, which do not need to be tagged. For example, radar, lidar, or ultrasonic sensing can provide such distance information with respect to near-by and untagged objects. Whenever such second monitoring device raises a warning, such warning provides additional information to the person in charge based on the knowledge of the different sensing principles. This is why it may be advantageous for any operator of e.g. large vehicles in a mine to be in a position to distinguish a warning stemming from a GNSS based proximity measurement system to a warning from a non-GNSS distance measurement system, preferably based on runtime evaluation. In case, only the second proximity warning is issued but not the first, the operator can derive that there potentially is an object close by not being

equipped with a GNSS based receiver such that it may be necessary to stop immediately. On the other hand, in case only the GNSS based receiver indicates a - tagged - ob- ject but the second monitoring device does not - provided both devices look into the same direction - the operator can derive that the situation may not be of immediate danger (yet) .

Other preferred embodiments of the present invention are stipulated in the dependent claims. Such embodiments refer to the appearances which enable the warnings to be differentiated, or refer to a possible cross-relationship between warnings and monitoring units. Other dependent claims refer to the various embodiments of the second monitoring device.

According to another aspect of the present invention, a method is provided for generating a proximity warning. The method comprises determining the position of an object to which a first monitoring device with a receiver for a radio based positioning system is mounted to, measuring the distance to another object by means of a second monitoring device, issuing a first proximity warning in dependence of the determined position, and issuing a second proximity warning in dependence of said measured distance, wherein said first prox- imity warning and said second proximity warning are issued by a common output device.

In another aspect of the present invention, a method is provided directed to deploying the disclosed system to an entire area such as a mining site. A plural- ity of first monitoring devices are provided, wherein at least some of said first monitoring devices are installed on objects operating in said area, wherein at least part of said first monitoring devices comprise a receiver for a radio based positioning system and a radio circuit, and at least one second monitoring device installed on one of the objects comprising at least one of said first monitoring devices, wherein said second monitoring device measures the distance to another object. In such environment, by means of said first monitoring device, a first device status dataset depending on a position of said first monitoring device is generated and emitted through the radio circuit of said first monitoring device. A de- vice status datasets from monitoring devices installed on other objects is received by said first monitoring de^¬ vice. From said first device status dataset and at least one of the received device status datasets a distance and an orientation between the present object to the other object is determined such that based on the determined distance a first proximity warning may be issued. A sec^¬ ond proximity warning may be issued in dependence of a distance measured by the second monitoring device. Again, first and second proximity warnings are issued by a common output device.

Consequently, a system and a method are disclosed for generating a proximity warning. Based on two different sensing principles proximate objects can be detected by respective monitoring devices. The warning system is designed such that each monitoring device issues a warning via a common output device being fed by signals originating from the monitoring devices.

The described embodiments similarly pertain to the system, the method, and the apparatus. Synergetic effects may arise from different combinations of the embodiments although they might not be described in detail.

Further on it shall be noted that all embodiments of the present invention concerning a method might be carried out with the order of the steps as described, nevertheless this has not to be the only essential order of the steps of the method all different orders of orders and combinations of the method steps are herewith described.

Brief Description of the Drawings

The aspects defined above and further as- pects, features and advantages of the present invention can also be derived from the examples of embodiments to be described hereinafter and are explained with reference to examples of embodiments. The invention will be described in more detail hereinafter with reference of examples of embodiments but to which the invention is not limited.

Fig. 1 shows a schematic representation of a site .

Fig. 2 is a block diagram of a system according to an embodiment of the present invention.

Fig. 3 is a schematic top view on a vehicle equipped with four second monitoring devices according to an embodiment of the present invention.

Fig. 4 illustrates an optical display according to an embodiment of the present invention. Modes for Carrying Out the Invention

Similar or relating components in the several figures are provided with the same reference numerals.

A "movable object" is any object that can change and is expected to change its position and/or orientation or configuration in space. It may e.g. be a truck or any other vehicle that moves from place to place and changes its orientation in respect to the general north-south direction, e.g. by steering, or it may be an object positioned at a fixed location but able to rotate about its axis or to change its physical configuration, e.g. by extending an arm, in such a manner that the volume of safety space attributed to it varies in significant manner.

The term GNSS stands for "Global Navigation

Satellite System" and encompasses all satellite based navigation systems, including GPS and Galileo.

The term "radio based positioning system" stands for a GNSS or for any other type of positioning system based on radio signals, such as a pseudolite system, a WiFi based Real Time Location System (RTLS) , etc. Fig. 1 schematically depicts a site 1, such as a surface mine, to be monitored by the present system. The figure primarily shows the components relevant in the context of the present invention. Typically, such a site covers a large area, in the case of a surface mine e.g. in the range of square kilometers, with a network of roads 2 and other traffic ways, such as rails 3. A plurality of objects is present in the mine, such as:

- Large vehicles, such as haul trucks 4a, cranes 4b or diggers 4c. Vehicles of this type may easily weigh several 100 tons, and they are generally difficult to control, have very large breaking distances, and a large number of blind spots that the driver is unable to visually monitor without monitoring aids, such as e.g. cameras.

- Medium sized vehicles 5, such as regular trucks. These vehicles are easier to control, but they still have several blind spots and require a skilled driver .

- Small vehicles 6. Typically, vehicles of this type weigh 3 tons or less. They comprise passenger vehicles and small lorries.

- Trains 7.

A further type of object within the mine is comprised of stationary obstacles, such as temporary or permanent buildings 9, open pits, boulders, non-movable excavators, stationary cranes, deposits, etc.

The risk of accidents in such an environment is high. In particular, the large sized vehicles can eas- ily collide with other vehicles, or obstacles.

For this reason, the mine 1 is equipped with a monitoring equipment that allows to generate proximity warnings for the personnel of the site, thereby reducing the risk of collisions and accidents.

Basically, the each of the objects comprises at least one first monitoring device 12 which includes a radio based positioning system interacting with satel- lites 16. These devices 12 communicate in wireless manner, in particular by radio signals.

The first monitoring devices 12 are e.g. installed on the objects 4 - 7, and 9.

An exemplary system according to an embodiment of the present invention is shown in a block diagram in Fig. 2. The system comprises a control unit 14, such as a microprocessor system, which controls the operations of the system, and in particular controls an output de- vice 19.

The system 15 further comprises a first monitoring device 15 in form of a GNSS receiver. Although it is called a GNSS receiver in the following, it can also be a receiver interoperating with any other radio based positioning system for determining its position. The present invention can be used on various types of radio based positioning systems.

The system 15 further comprises a second monitoring device 40. The second monitoring device 40 is a radar device for determining the distance to a near by object, such as within the range of e.g. 10 - 20 meters, by means of the radio detection and ranging concept as known to those skilled in the art.

The system 15 further comprises a radio transceiver or circuit 17 for exchanging data with other parts of the monitoring apparatus, e.g. with other systems 12.

A control unit 14 accesses a memory 18 that comprises programs as well as various parameters, such as a unique identifier of the monitoring devices 12 and 40.

The output device 19 advantageously comprises output elements such an optical display 20 using LED's, LCD's, etc. as well as an acoustic signal source 21, such as a beeper. In addition, such output device 19 may com- prise another speaker via which electronically generated voice messages may be issued as warnings. Proximity warnings can, e.g. be issued by the optical display 20 that can be observed by the user and/or an acoustic signal. In addition, the acoustic signal source 21 can generate voice data and/or other types of sound. The control unit 14 may also be part of the output device 19. Output device 19 including output elements 20, 21 and control unit 14 in an embodiment can be arranged in a common housing. In another embodiment, only the output elements are arranged in a common housing, and the control unit may be located remotely. The control unit 14 may evaluate the data received from the monitoring devices 12 and 40 and may generate signals supplied to the output device 19 for generate or triggering the warnings. In another embodiment, the common output device may be embodied such that at least one of the output elements is designed for issuing both, the first and the second proximity warning.

The primary purpose of the system 15 is to generate proximity warnings in case that there is a danger of collision. As mentioned in the introduction, this is achieved by receiving at least positional signals through GNSS receiver and exchanging data derived therefrom with other systems in order to calculate relative positions and probabilities for collisions, and by receiving distance signals through the radar device. Any data supplied by the monitoring devices in general, or subject to specific thresholds, may be logged in a log 60. The log 60 may also be integral part of the memory 18. In the log, different data may be recorded: It may be such that the positional data and/or the distance data may be recorded continuously or triggered by one of the data fulfilling a criterion such as the distance being less than a threshold which may indicated an upcoming crash. And/or, the signals generated by the control unit 14 for triggering the warnings may be recorded. Any log may help in later verifying why a crash may have happened, and may verify the proper operation of the system.

In addition, in a preferred embodiment, a detection device for detecting fatigue of the operator / driver may be provided and integrated into the overall system such that the first warning and / or the second proximity warning may depend on a signal from such fatigue detection device. In another embodiment, such fa- tigue detection device may be in a position to issue a separate warning itself.

The operation of the first monitoring devices can be basically as in conventional systems of this type, such as e.g. described in WO 2004/047047 and need not be described in the very detail herein. In short, in a simple approach, each device obtains positional data derived from a signal from GNSS receiver. This positional data allows determining the position of the device and is stored in a "device status dataset". The device status dataset also contains a unique identifier (i.e. an identifier unique to each of the first monitoring devices 12 used on the same site) . The device status dataset is emitted as a radio signal through transceiver 17. At the same time, the device receives the corresponding signals from neighboring devices and, for each such neighboring device, it calculates the relative distance d by subtracting its own coordinates from those of the neighboring device.

A proximity warning triggered by the posi- tional information - which for the first monitoring device includes distance information with respect to another object, too for the reason that the distance is determined by differences in the position of the two objects in question - can be generated by means of various algorithms. Examples of such algorithms are described in the following. In a very simple approach, it can be tested if the absolute value of the relative distance d is below a given threshold. If yes, a proximity warning will be issued. This corresponds to the assumption that a circular volume in space is reserved for each object. The radius of the circular volume attributed to an object can e.g. be encoded in its device status dataset. A more ac- curate algorithm can e.g. take into account not only the relative position, but also the driving velocities and directions of the vehicles. An improvement of the prediction of collisions can be achieved by storing data in- dicative of the size and/or shape of the vehicle that a monitoring device is mounted to. This is especially true for large vehicles, which may have non-negligible dimensions. In a most simple embodiment, a vehicle can be modeled to have the same size in all directions, thereby de- fining a circle/sphere "covered" by the vehicle. If these circles of spheres of two vehicles are predicted to intersect in the near future, a proximity warning can be issued. Instead of modeling an object or vehicle by a simple circle or sphere, a more refined modeling and therefore proximity prediction can be achieved by storing the shape (i.e. the bounds) of the vehicle in the dataset or by determining the same dynamically as in the embodiments described below. In addition, not only the shape of the vehicle, but also the position of the GNSS-receiver (or its antenna) in respect to this shape or bounds can be stored in memory 18.

The second monitoring device 40 - which is not shown in Figure 1 but is assumed to be present on many of the vehicles for monitoring the vicinity in at least one direction - may issue e.g. via a control unit for evaluating the measured distances a warning signal which triggers the output device to issue the second proximity warning when the distance is less than a threshold, e.g. less than 5 meters. Subject to the meas- uring principle used and the range of interest to be scanned the maximum range within which another object can be detected, e.g. in a runtime measurement measuring the time between issuance of a signal, be it a radio signal, a light signal - in particular a laser signal-, or a sonic signal - in particular an ultrasonic signal -, and the receipt of the signal reflected at the remote object, may be preferably less than twenty meters. The advantage of such monitoring devices is that in contrast to the GNSS based devices the remote object needs not to be tagged or equipped with any detection unit. This is why such a monitoring device ideally complements the GNSS based monitoring device. Preferably, the second monitoring device is based one of radar, lidar and sonic technology for determining the distance to a near-by object.

Alternatively, or in addition to evaluating the distance to other objects by means of these objects having GNSS receivers installed, too, the corresponding positional information of these objects being transmitted to the present object, and a distance value being derived from the positional information of the present and the other object, the positional information of the present object can also be compared to positional information of preferably stationary objects electronically stored in a map 50 as shown in Figure 2. The map 50 may include information on stationary objects of a site, and the control unit 14 may be designed for determining a distance between the current position of the present object from e.g. stationary objects derived from such map 50. The output device 19 may be designed for issuing the first proximity warning when such distance is less than a threshold .

When it comes to the arrangement of the second monitoring device (s) at an object, it is advantageous to address each side of the object with a second monitoring device. In this sense, Figure 3 illustrates a schematic top view on a vehicle 6 equipped with four second monitoring devices 40 in form of lidar devices, one located at each side of the vehicle 6. Alternatively, the lidar devices 40 can be located at the edges of the vehicle 6. Both arrangements are beneficial for covering a large area in the vicinity of the mobile object for prox- imity and/or collision detection purposes.

In such arrangement, the warnings based on information delivered by one of the second monitoring de- vices 40 may preferably allow for an indication which one of the several second monitoring devices 40 has detected an object near-by resulting in the warning. Preferably, the warnings issued by the several second monitoring de- vices 40 can be distinguished. For example, the warning assigned to the second monitoring devices 40 is an optical warning issued by an optical display 20 in form of multiple LEDs (light emitting diode) , as shown in Figure . An output device - understood as combination of sev- eral output elements be it visual or acoustic including speech based warning elements - may include the optical display 20 including four LEDs 200, 201, 202, 203 arranged in the corners of a virtual square or on a virtual ring by this indicating a direction, for example in rela- tion to a forward moving direction of the vehicle. Whenever the radar device to the right hand side in Figure 3 causes issuing a second warning the corresponding LED 201 to the right hand side of the optical display 20 is flashing. Whenever the radar device to the left hand in Figure 3 causes issuing a second warning the corresponding LED 203 is flashing, etc. By this the operator is aware to which side of the vehicle another object is close by. In addition to the four LEDs 200 - 203 representing warnings triggered by the second monitoring^■ de- vices 40, the first monitoring device 12 is assigned two more rings /squares of LEDs 300 - 303 and 400-403 in the optical display 20. Provided the first monitoring device 12 is capable for identifying other tagged objects not only with respect to the distance but also with respect to the direction, the middle ring of LEDs 300-303 is assigned to the first monitoring device detecting a tagged object in the mid-range, and the outer ring of LEDs 400 - 403 may be assigned to an object detected in a far range by the first monitoring device 12. Overall, such visual warning system may comprise three LEDs per direction, two of which are assigned / connected to the first monitoring device 12, the last one being assigned to the second monitoring device 40 such that the operator always is in a position to determine which monitoring device 12, 40 is issuing a warning. In addition, each ring of LEDs may have a different colour than another ring of LEDs. For example, the LEDs 200 - 203 of the inner ring may flash in a warning colour such as red, while the LEDs 400 - 403 of the outer ring may flash in a colour different to red, such as green, indicating that no immediate action may be required, while the colour of the LEDs 300 - 303 in the middle ring may be yellow for example, indicating medium risk. Instead, or in addition, the LEDs may flash with different frequencies, the higher the risk, the higher the frequency. Instead of the LEDs, there may be provided other visual elements, such as warning symbols, text, or other signs, arranged as individual elements, or, combined, on a display.

Also, the position of the first and the second visual proximity warnings may be differently arranged, e.g. on a common flat panel display.

In general, the first and the second proximity warnings are preferably different in their appear^¬ ance for better enabling an operator to immediately assess the risk associated. This not only holds for the warnings being embodied as visual warning. Instead the first proximity warning may be a visual warning, whereas the second proximity warning may include an acoustic warning in addition to a visual warning, or an acoustic warning exclusively. An acoustic warning may be a beep or any other sound drawing attention to the monitoring sys- tern. In another embodiment, it may even be that both proximity warnings include acoustic warnings. Again, such acoustic warnings then differ, for example, in their volume, their frequency, their beeping frequency, their sound, etc.

According to another aspect of the present invention, there is provided that an appearance of the first proximity warning is variable subject to said loca- tion/distance data. Such embodiment is already described with respect to the above LED display. The same may apply to an appearance of second proximity warnings which may be variable subject to said distance data. In an optical display such as the one above, there may be provided another ring of four LEDs arranged as a very inner ring which for example flashes at high frequency whenever an object detected by the second monitoring device is, for example, closer than two meters from the object holding the first and the second monitoring devices 12, 40.

According to another preferred embodiment, the second and/or first proximity warning may be modified in its appearance subject to the positional data supplied by said first monitoring device.

Similar to the above, said first and/or second proximity warning can also be modified in its appearance subject to said distance data supplied by said second monitoring device.

In another embodiment, the second proximity warning is modified in its appearance subject to previous distance data. For example, in a scenario, where a digger is digging close to a wall which most often is not equipped with the first kind of a monitoring device, the second monitoring device will cause issuance of warnings each time the digger approaches the wall, although the operator is already aware of this obstacle. In order not to distract the operator by ongoing warnings, the system may be embodied such that whenever the distance to an object frequently appears within a certain time period, it can safely be assumed that the operator is aware of such obstacle such that the second warning is suppressed or modified such that its intensity decreases with each new approach. Such logic in particular can be combined with the positional information received from the first moni- toring device: Whenever the position of the digger remains in about the same area and the above approach scenario occurs, it can even more safely be assumed that the obstacle is a permanent one being noticed by the operator already.

Such concept may also apply to a modification of the first warning, e.g. whenever a huge building is equipped with a GNSS based receiver, and a vehicle is being run in an area close to such building, the first proximity warning may be modified in its appearance subject to previous positional data allowing for an interpretation that the vehicle currently is operating near and such building and the operator is aware of this.

In general, such modification of a proximity warning may, e.g. include a complete suppression of the warning, or, in case of an acoustic warning include one of a decrease and an increase in at least one of the vol- ume and the alternating frequency and the frequency spectrum of said respective acoustic warning, or in case of a visual warning include one of a decrease and an increase in one at least one of the intensity, the color, the flashing frequency, the representation of warning sym- bols, the position on the output device, and the appearance of said respective visual warning.

While there are shown and described presently preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited the- reto but may be otherwise variously embodied and practiced within the scope of the following claims.

Claims

1. A system for generating a proximity warning, comprising

a first monitoring device (12) comprising a receiver for a radio based positioning system for determining the position of an object the first monitoring device (12) is mounted to,

a second monitoring device (40) for measuring the distance to another object, and

a common output device (19) for issuing a first proximity warning in dependence of positional data supplied by said first monitoring device (12), and for issuing a second proximity warning in dependence of dis- tance data supplied by said second monitoring device (40) .

2. A system according to claim 1, wherein said second monitoring device (40) is designed for measuring the distance to said other object not being

equipped with a monitoring device corresponding to said first monitoring device (12) .

3. A system according to claim 1 or claim 2, wherein said output device (19) is designed for issuing said first proximity warning in dependence of said posi- tional data derived from a signal from said first receiver and of device status datasets received from other devices .

4. A system according to any one of the preceding claims, wherein said first proximity warning is different to said second proximity warning.

5. A system according to any one of the preceding claims, wherein at least one of said first proximity warning and said second proximity warning includes a visual warning.

6. A system according to claim 5, wherein said first and said second proximity warning each includes a visual warning, and wherein said first and said second proximity warning differ in at least one of their color, their flashing frequency, their representation of warning symbols, their position on said output device

( 19 ) , and their appearance.

7 . A system according to any one of the preceding claims, wherein at least one of said first and said second proximity warning includes an acoustic warning .

8 . A system according to any one of the pre- vious claims, wherein an appearance of at least one of said first proximity warning and said second proximity warning is variable subject to said distance data.

9 . A system according to any one of the preceding claims, wherein said second proximity warning is modified in its appearance subject to said positional data supplied by said first monitoring device ( 12 ) .

10 . A system according to any one of the pre^¬ ceding claims, wherein said first proximity warning is modified in its appearance subject to said distance data supplied by said second monitoring device ( 40 ) .

11 . A system according to any one of the preceding claims, wherein at least one of said first proximity warning and said second proximity warning is modified in its appearance subject to previous distance data.

12 . A system according to any one of the pre^¬ ceding claims, wherein at least one of said first proximity warning and said second proximity warning is modi^¬ fied in its appearance subject to previous positional data .

13 . A system according to any one of the preceding claims 9 to 12 , wherein said modification includes a suppression of said respective warning.

14 . A system according to any one of the preceding claims 9 to 12 , wherein said modification includes at least one of a decrease and an increase in at least one of the volume and the alternating frequency and the frequency spectrum of said respective acoustic warning.

15. A system according to any one of the preceding claims 9 to 12, wherein said modification includes a modification in at least one of the color, the intensity and the flashing freguency, the representation of

₅ warning symbols, the position on said output device (19) , and the appearance of said respective visual warning.

16. A system according to any one of the preceding claims, wherein said second monitoring device (40) comprises a runtime measurement device.

o 17. A system according to any one of the preceding claims, wherein said second monitoring device comprises (40) at least one of a radio detection and ranging device, a light detection and ranging device, and a sound detection and ranging device.

s 18. A system according to any one of the preceding claims, comprising multiple second monitoring devices (40) for measuring distances to other objects in various directions with respect to the object said second monitoring devices (40) are mounted to.

o 19. A system according to any one of the preceding claims, comprising a map (50) including information of stationary objects of a site, wherein said output device (19) is designed for issuing said first proximity warning in dependence of said positional data derived₅ from a signal from said first receiver and of stationary object data derived from said map (50) .

20. A system according to any one of the preceding claims, comprising a control unit (14) for receiving signals from said first and said second monitoring0 device (12, 40) and for generating signals resulting in said first and said second proximity warning.

21. A system according to claim 20, wherein said output device (19) comprises said control unit 21.

22. A system according to any one of the pre-5 ceding claims, wherein said output device (19) comprises multiple output elements (20, 21) designed for issuing said proximity warnings.

23. A system according to claim 21 or claim 22, wherein said output device (19) comprises a housing, and wherein at least one of said control unit (14) and said output elements (20, 21) are arranged in/at said housing.

24. A system according to any one of the preceding claims, comprising a control unit (14) for generating device status datasets, wherein said device status datasets comprise positional data derived from a signal of said receiver, and comprising a radio circuit (17) for broadcasting said device status datasets to other monitoring devices.

25. A system according to claim 20, wherein said control unit (14) is designed for generating said signal resulting in said second proximity warning when said distance data shows a distance less than a predetermined threshold.

26. A system according to claim 20 in combination with claim 3, wherein said control unit (14) is designed for generating said signal resulting in said first proximity warning when said positional data in combination with said device status datasets received from other devices indicates a distance to another object less than a predetermined threshold.

27. A system according to any one of the preceding claims, comprising a log (60) for logging at least one of said positional data, said distance data, and said signal resulting in one of said first and said second proximity warning.

28. A movable object, comprising a system of any of the preceding claims, wherein said first and said second monitoring devices (12, 40) are mounted to said movable object, and wherein said movable object is one of the group consisting of vehicles (5, 6), cranes (4b), draglines, haul trucks, diggers (4c) and shovels.

29. A method for generating a proximity warning, comprising determining the position of an object to which a first monitoring device (12) with a receiver for a radio based positioning system is mounted to,

measuring the distance to another object by means of a second monitoring device (40),

issuing a first proximity warning by a common output device (19) in dependence of the determined position,

issuing a second proximity warning by said common output device (19) in dependence of said measured distance .