WO2011010154A2

WO2011010154A2 - System and method for monitoring activity of an operating device on a geographical scale

Info

Publication number: WO2011010154A2
Application number: PCT/GB2010/051205
Authority: WO
Inventors: Stephen Paul Birdsall
Original assignee: Gaist Ltd
Priority date: 2009-07-24
Filing date: 2010-07-21
Publication date: 2011-01-27
Also published as: GB2472076B; WO2011010154A3; GB2472076A; GB0912864D0

Abstract

System and method for monitoring activity of an operating device on a geographical scale A method of monitoring activities on geographical scale is disclosed. In this context, "geographical scale" means a scale that would normally be represented on geographical maps, typically in the order of hundreds of meters to hundreds of kilometres. The method involves capturing a track to describe a path of a device that is performing an operation using a global navigation system receiver; associating with the track data that represents operational status of the device; and identifying elements within a segmented digital map that contain part of the captured track; wherein each element has zero or more attributes associated with it that define a set of activities to which the element can be subjected. The attributes indicate that the element can be subject to the operation performed by the tracked device, the element is tagged to indicate that the operation has been performed upon it. The device being tracked is typically carried on a vehicle. The method is typically performed in a software program that can display the map, the segments, and the processed information that describes the track on a visual display unit.

Description

System and method for monitoring activity of an operating device on a geographical scale

This invention relates to systems and methods for monitoring activity of an operating device on a geographical scale. In this context, "geographical scale" means a scale that would normally be represented on geographical maps, typically in the order of hundreds of meters to hundreds of kilometres. The development of cheap and robust location devices that can determine their position using signals from a global navigation satellite system (GNSS) has led to the widespread application of such devices to track the movements of a large range of objects on a geographical scale. The range of applications has extended far beyond those initially intended for such systems, and as a result, the limitations of such systems (at least insofar as their capabilities are made publicly available) have become apparent. In particular, the absolute positional accuracy may be insufficient for some applications.

One approach to improving the apparent accuracy of a GNSS is to use Kalman filtering, which attempts to synthesise a smooth track from a sequence of points that are known to include an element of random noise. Such a track can then be superimposed upon a map to describe a path in a geographical realm, as shown in Fig l. However, even when such an approach is used to provide improvements to a GNSS track, the result is still a one-dimensional line of, effectively, zero width. This is a limitation where the aim is to record an operation that is performed over a two- dimensional area. For example, if the aim is to track operation of a vehicle that carries a device for surveying a road surface, then the result should be a description of a two-dimensional area of road that has been surveyed. An aim of this invention is to provide systems and methods that can improve the usefulness of data derived from a GNSS.

From a first aspect, the invention provides a method for monitoring activities on geographical scale comprising: a. capturing a track to describe a path of a device that is performing an operation using a global navigation system receiver; b. associating with the track data that represents operational status of the device; c. identifying map elements within a segmented digital map that contain part of the captured track; wherein each element has zero or more attributes associated with it that define a set of activities to which the element can be subjected; and d. where the attributes indicate that the map element can be subject to the operation performed by the tracked device, the map element is tagged to indicate that the operation has been performed upon it.

The method ensures that only map elements that are capable of having a particular method performed on them are marked as having had that operation performed on them. For example, a map element that contains only an area of grass cannot be marked as having been cleaned by a street cleaner. Advantageously, the size of a map element can be less than the accuracy that can be reliably obtained from the global navigation receiver. This may mean that the track is sometimes identified as being in a map element that the device did not occupy, but the method does not allow this to result in meaningless data being added to that map element. In preferred embodiments, all of the map elements are of an identical shape and size. For example, they may all be squares. Each map element may have a side dimension of several metres, for example, 2m.

It is preferable that one or more additional elements adjacent to an element that contains a track are tagged to indicate that the operation has been performed upon them. This extends the one-dimensional track to an area. The additional elements are typically tagged only if they contain attributes that indicate that the element can be subject to the operation performed by the tracked device. Moreover, the additional elements are typically tagged only if they are less than a maximum distance from an element that contains the track. This distance corresponds to a maximum width of operation of the tracked device. Additional elements may be tagged only if they are adjacent to an element that contains the track or to an additional element that has already been tagged. Thus, the total marked area is contiguous. The cell may not be uniform. That is, different parts of the cell may have different attributes. Where this is the case, the cell may be subdivided into two or more smaller elements, each of which may have one or more different attributes. (In many cases, simply reducing the grid size used for all elements would increase the size of the data unnecessarily. Typical embodiments of the invention use a global navigation satellite system to capture the track. For instance, the Global Positioning System may be used.

From a second aspect, this invention provides apparatus to be carried on a vehicle for use in a method according to the first aspect of the invention, the apparatus comprising a global navigation system receiver, monitoring means for monitoring an operational system of the vehicle and data recording means for recording the output of the global navigation system receiver and of the monitoring means.

The apparatus may further include data transmission means for transmitting data recorded by the recording means to a data processing system. -A-

From further aspects, the invention may also provide a software program that can be executed to perform a method according to the first aspect of the invention, and a computer system that includes such a program and hardware for executing it.

A computer system embodying this aspect of the invention is typically operational to generate a display that represents the digital map. The representation of the map may further include an overlaid grid that indicates borders of the grid elements. The display may represent attributes of elements by applying to them a colour, a shading, or a hatching or another suitable graphical property.

An embodiment of the invention will now be described in detail, by way of example, and with reference to the accompanying drawings, in which:

Figure i shows a GNSS track superimposed on a geographical map, and has already been discussed;

Figure 2 is a screenshot of a street map that has been generated by an embodiment of the invention; Figure 3 shows, schematically, a vehicle equipped for use in an embodiment of the invention; and

Figure 4 is a flowchart that describes the process of the embodiment of the invention.

This embodiment of the invention provides a system for tracking the activities of a vehicle 10 that carries equipment 12 that can be operated to clean the carriageway of an urban road, as might typically be operated by a local authority. In order to demonstrate that the authority is meeting its statutory obligations, it is desirable that it can demonstrate that its cleaning of their highways has been carried out comprehensively. To this end, the vehicle is also provided with a receiver 20 that can periodically determine the position of the vehicle using a global navigation satellite system (GNSS) and log the position of the vehicle together with a time stamp in a database, along with other potentially relevant information, such as the speed or velocity of the vehicle 10 and the quality of the signal received from the GNSS (Step l). The vehicle is also provided with sensors 22 that can monitor aspects of its operation, such as whether it is cleaning or in transit. A controller 24 is provided that can capture and store data from the receiver 20 and sensors 22. The vehicle also carries a data transmitter 26 whereby the controller 24 can send its data to a remote processing centre using cellular telephony.

The data recorded while the vehicle is in operation to represent its track is compiled into a data set that further includes metadata to represent the identity of the vehicle, its crew and other aspects of the operational status of the vehicle (Step 2). For example, if the vehicle is a road sweeper, the metadata may specify its mode of operation at any given time - whether it is sweeping the road or in transit between sweeping locations. The data set is then returned to a central system for processing (Step 3). The data may be returned in real time (for example, using cellular telephony) or transferred in a batch once the vehicle has completed a period of operation.

Once the data has been received and stored (Step 4) by the central system, it can be processed using a multiplicity of techniques to extract relevant information from it. In a number of these techniques, the data received by the central system is associated with a geographical map before being presented to a user, whereby a user can gain an understanding of the geographical range over which the activities of the vehicle have taken place. For convenience, the geographical map is divided into a multiplicity of uniformly-shaped (in this example, 2m square) grid elements, each of which can have an associated set of attributes that make up a cell profile. For instance, an attribute may be set to indicate that a particular process (such as inspection of a road surface) has taken place within the grid element.

A technique implemented by this embodiment that will be referred to as the "navigation envelope method" (abbreviated as NEM) will now be described. The NEM is a method by which the embodiment processes the incoming data such that the system recognises the real-world activity associated with the incoming data. The aim of the NEM is to determine which elements in the grid are to have their attributes set in response to the track of the vehicle. This means that the NEM must transform the one-dimensional track (with its inherent noise and errors) into a two- dimensional area comprising multiple grid elements. By using a combination of Kalman filtering and an understanding of the cell profiles in the NEM, it is possible to map the data to a range of cells that are most likely to match up with the actual activity carried out.

In this embodiment of the NEM, positional information contained in the data representing the track is processed using a simple Kalman filter (Step 6) to provide an accurate, continuously updated description of the position and velocity of the vehicle given only a sequence of observations about its position, each of which includes some level of error. It is to be expected that the positional signal recorded by the GNSS will often be degraded by multi-path interference and other noise, therefore the use of Kalman filtering (or a functional equivalent of it) will be essential. The Kalman filter exploits the dynamics of the vehicle (and is modified in accordance with the expected properties of the vehicle (Step 5)), which govern its time evolution, to remove the effects of the noise and get a good estimate of the location of the vehicle at an instant in time (filtering), at a future time (prediction), or at a time in the past (interpolation or smoothing). The 'smoothed' track of the vehicle track obtained from the Kalman filtering operation is then processed along with associated metadata pertaining to the role of the vehicle (Step 7).

Returning to the example of a road sweeper, while its status is "in transit", it has no effect upon its environment, so those parts of the track that are identified as "in transit" do not cause associated parts of the map to be updated with a "cleaned" flag. For those parts of its track during which the status of road sweeper is "sweeping", associated grid elements should be flagged as having been swept at the time that the sweeper passed through it. This assumes that the track actually represents the real path of the vehicle. The aim of the NEM is to ensure that only grid elements that are pertinent to the activity are populated, even if the vehicle track plot is inaccurate to such a degree that might mean that its recorded track deviates by more than a whole grid element. In accordance with this embodiment, each grid element has associated with it one or more attribute flags that indicate the type of action that might meaningfully be performed upon it. In this example, a grid element that includes a vehicle carriageway would have a "can be cleaned by a road sweeper" flag associated with it (Step 8). In contrast, a grid element that contains only a grass lawn would not have such a flag set. Therefore, in this example a grid element is updated with a "cleaned" flag if a. the track of the road sweeper passes through it; b. the metadata indicates that the status of the sweeper is "sweeping"; and c. the grid element has a flag set that indicates it is an element that can be cleaned by a road sweeper. Such a cell is termed the "master cell" (Step 9).

Note that any cell may have an arbitrarily large number of flags associated with it. For example, a vehicle carriageway may have flags including "can be cleaned by a road sweeper", "can be inspected for potholes", "can be re-surfaced", and so forth.

In some cases, marking of serviced grid elements may extend to elements adjacent to the master cell in which the track is present where these elements have the appropriate flag. As an example, if a footway sweeper is being tracked, the marked cells will extend to the entire width of the footway, up to a maximum operational width of the sweeper (say, 5 m), provided that these adjacent cells are flagged as being capable of being swept by a footway sweeper (Step 10). It is safe to assume that the whole footway will be cleaned in one pass. In reality it may have missed some small areas of the footway, but this is not something that can be recorded with sufficient accuracy. In areas where the footway is wider than say 5 m, for example in shopping precincts, then the system will populate a swath of cells 2.5 m either side of the GPS position for the sweeper. In a similar manner, on carriageway sweepers and other devices that are carried on a road vehicle, the system can be configured to populate all the cells attributed to the carriageway, with an optional limit being placed on the maximum effective width of the operation. Extension of tagging beyond the master cell containing a track is shown at 34 in Figure 2. A grid element may incorporate areas that have several different types of content. Such a grid element is shown at 32 in Figure 2, which cell includes both footway and carriageway. In such cases, the grid element is split into separate representative elements that approximately map the shape of the areas within the cell. The system then only attributes the 'operational' information to the corresponding area within the cell. The embodiment includes rules so it only does this 'sub cell' calculation if the sub cells are less than a user definable size, say 0.3m x 0.3m. Effectively, the size of the grid is reduced locally where additional detail is required to present the data with sufficient accuracy. In practical implementations, the data generated by the methods described above will be stored in a database (Step 11). This allows the data to be used for a wide range of purposes. Since the data is logically associated with a geographic map, it can be presented to a user in the form of an annotated graphical map incorporated into a web page that can be accessed remotely. For example, by representing those cells that have been subject to an operation being represented in a different colour from those that have not. Since the data has encoded within it a geographical location, it can readily be associated with other sources of geographical information to increase its usefulness (Step 12).

The data can be represented in the form of a suitably annotated map, as shown in Figure 2 displayed on a computer screen. As will be seen in the Figure, the map shows the outline of streets in a residential area. The main map segments are represented as a rectilinear grid of fine lines superimposed upon the map. Attributes of the elements and sub-cells are represented by application of shading and/or colour to the representation. In Figure 2, the attribute "can be cleaned by a road sweeper" is represented by horizontal hatching, while those elements marked as "swept" are shown with diagonal hatching. In practice, this is likely to be indicated by use of different colours within the image. It will be seen that in the regions indicated at 36, the sweeper was operational only on the carriageway of a road, while at 38, the sweeper was operational on both the carriageway and the footway. The position of the vehicle is also represented at 40.

Claims

1. A method of monitoring activities on geographical scale comprising: a. capturing a track to describe a path of a device that is performing an operation using a global navigation system receiver; b. associating with the track data that represents operational status of the device; c. identifying elements within a segmented digital map that contain part of the captured track; wherein each element has zero or more attributes associated with it that define a set of activities to which the element can be subjected; and d. where the attributes indicate that the element can be subject to the operation performed by the tracked device, the element is tagged to indicate that the operation has been performed upon it.

2. A method according to claim i in which the size of a map element is less than the accuracy that can be reliably obtained from the global navigation receiver.

3. A method according to any preceding claim in which all of the map elements are of an identical shape and size.

4. A method according to claim 3 in which each map element is a square.

5- A method according to claim 3 or claim 4 in which each map element has a side dimension of approximately 2m.

6. A method according to any one of claims 3 to 5 in which one or more map element is subdivided into a plurality of smaller elements.

7- A method according to any preceding claim in which one or more additional elements adjacent to an element that contains a track are tagged to indicate that the operation has been performed upon them.

8. A method according to claim 7 in which the additional elements are tagged only if they contain attributes that indicate that the element can be subject to the operation performed by the tracked device.

9. A method according to claim 7 or claim 8 in which the additional elements are tagged only if they are less than a maximum distance from an element that contains the track.

10. A method according to any one of claims 7 to 9 in which additional elements are tagged only if they are adjacent to an element that contains the track or to an additional element that has already been tagged.

11. A method according to any preceding claim in which different areas of a cell have different attributes.

12. A method according to any preceding claim in which a global navigation satellite system is used to capture the track.

13. A method according to claim 11 in which the global navigation satellite system is the Global Positioning System.

14. A computer system that includes a software program that can be executed to perform a method according to any preceding claim.

15- A computer system according to claim 15 that is operational to generate a display that represents the digital map.

16. A computer system according to claim 16 in which the representation of the map further includes an overlaid grid that indicates borders of the grid elements.

17. A computer system according to claim 16 or claim 17 in which the display represents attributes of elements by applying to them a colour, a shading, or a hatching.

18. Apparatus to be carried on a vehicle for use in a method according to any preceding claim, the apparatus comprising a global navigation system receiver, monitoring means for monitoring an operational system of the vehicle and data recording means for recording the output of the global navigation system receiver and of the monitoring means.

19. Apparatus according to claim 19 further including data transmission means for transmitting data recorded by the recording means to a data processing system.