GB2373577A

GB2373577A - Global positioning apparatus and data logger for use therewith

Info

Publication number: GB2373577A
Application number: GB0106815A
Authority: GB
Inventors: Martyn Draper; M Beddis; Ian D Prosser
Original assignee: Amey Railtech Ltd
Current assignee: Amey Railtech Ltd
Priority date: 2001-03-19
Filing date: 2001-03-19
Publication date: 2002-09-25
Also published as: GB0106815D0

Abstract

A global positioning apparatus for use in a data logger 10 for logging data relating to infrastructure systems, eg. a railway network comprising a global positioning unit 12 which, in use, measures the global positioning system position of the apparatus. Means for measuring the speed and direction of travel of the apparatus are also provided. The unit and the means are both in data communication with a central processing unit 26 which is provided with a position algorithm which, in use, predicts the global positioning system position of the apparatus from an earlier measured global positioning system position and the measurements of speed and direction of travel of the apparatus. Position prediction occurs when there is poor or no GPS coverage.

Description

Global positioning apparatus and data logger for use therewith The present invention relates to global positioning apparatus and a data logger which makes use of the global positioning apparatus, both for use, especially but not exclusively, in inspection and maintenance of infrastructure systems, especially railway networks.

Operators of infrastructure systems need to carry out regular inspections to determine where defects need to be repaired and maintenance work needs to be carried out. Previously, this was carried out entirely manually, with inspectors required to make notes on paper during the inspection, which were later transferred to files and maps.

Thus it was difficult to keep an up-to-date record of the state of the entirety of the system. The advent of computer networking has allowed maps to be stored electronically, updated more easily and quickly, and accessed by any person connected to the relevant computer network. However, a problem exists in that it is difficult to accurately transfer onto the map the exact location of defects noted on the ground during an inspection. Knowledge of exact locations is important as it allows repairs and other work to be carried out more quickly and efficiently.

Global positioning systems provide a way of determining the exact location of a spot on the ground, whilst at that spot. Thus, a global positioning system position combined

with details of a defect allow the defect to be accurately noted on a map.

Various devices, based on global positioning systems have been proposed which allow inspectors to determine the precise location of defects noted during an inspection. A number of disadvantages have been noted with respect to these systems. Some have been not included graphical information systems, and users have found that hence they do not provide sufficient feedback about position to be useful.

Systems which overcome this by providing a graphical display have tended to be based on existing conventional laptop-type computers, which, although designed to be portable within reason, tend to be too bulky, heavy and fragile to be easily carried and used during an inspection of, for example, a railway embankment. Additionally, such computers, which are battery powered, tend to suffer from short battery lifetimes, meaning that they cannot be used on the ground for long periods of time.

Furthermore, the positional information available from previously proposed devices has been unreliable, because it is not possible to obtain accurate positional measurements in areas with poor or no global positioning system coverage.

Accordingly, the present invention is directed to a global positioning apparatus for use in a data logger for logging data relating to infrastructure systems, comprising a global positioning unit which, in use, measures the global

positioning system position of the apparatus, means for measuring the speed and direction of travel of the apparatus, the unit and the means both being in data communication with a central processing unit which is provided with a position algorithm which, in use, predicts the global positioning system position of the apparatus from an earlier measured global positioning system position and the measurements of speed and direction of travel of the apparatus. This allows the apparatus to provide global positioning system position at all times, even when it is in an area with poor or no global positioning signal coverage.

Advantageously, the global positioning unit is nondifferential. Global positioning systems are described as either"differential"or"non-differential". Differential systems are very accurate, but are expensive to use as they rely on subscriptions to dedicated satellites and transmitter beacons to obtain position signals. Nondifferential systems are therefore to be preferred, and previously proposed infrastructure inspection devices have relied upon them. However, the positional information obtained by such devices has generally been poor, partly because of gaps in the global positioning signal coverage, and areas of poor signal coverage. Use of a non-differential unit in the present invention gives accurate positional information because the position algorithm calculates the position when no signal is available.

Preferably, the position algorithm is arranged such that if a predetermined time period has elapsed since a global positioning signal was received, the algorithm returns a message to inform the user that no valid position can be calculated. This offers the advantage that the user is alerted to any inaccuracies in the prediction of the global positioning system position which may arise if the algorithm has to predict position for a long period of time.

Hence, the accuracy of global positions ascertained by the apparatus is maintained.

The present invention is further directed to a data logger for logging data relating to infrastructure systems, comprising a global positioning apparatus as described above, and user interface apparatus, the central processor unit of the global positioning apparatus further being provided with means for transmitting and receiving global positioning system positions and data relating to the infrastructure system to/from a central controller, and the user interface apparatus comprising means for entering data, and a display screen for displaying global positioning system positions, infrastructure data and entered data. The data logger provides means for displaying on-site detailed information describing the section of the infrastructure to be inspected, and allows data relating to an inspection to be entered on site. The data/transmission reception means allows the data logger to be provided with the most up-to

date information about the infrastructure before inspection commences, and for data logged during the inspection to be incorporated into that held about the infrastructure quickly and simply after inspection.

Advantageously, the global positioning system positions and infrastructure data are combined and displayed in the form of a map of the infrastructure. A map is an especially advantageous way of displaying data relating to an infrastructure system, and facilitates use to the data logger.

Preferably, the display screen is touch-sensitive.

Positional information can be entered very simply by the user touching the relevant place on the map displayed on the screen.

In a preferred embodiment, the central processor unit is provided with a program for measuring the on-screen position of a touch on the touch sensitive screen, and software which relates the measured on-screen position to the infrastructure data to generate a location within the infrastructure map. Thus the data logger can calculate the position on the map which corresponds to the position touched on-screen.

Advantageously, the central processor unit is further provided with a calibration program which can compare a global positioning system position with a generated map location to produce a calibration factor, the factor then

being applicable to subsequent generated map locations to convert generated map locations to global positioning systems positions. In this way, any inaccuracies in map locations can be corrected in a continuous manner.

Preferably, the data logger further comprises data storage means for storing entered data and the global positioning system position at which data was entered. The stored data can be fed to the central controller after the inspection.

Advantageously, the data logger further comprises means for receiving radio frequency signals carrying positional information relating to infrastructure features. Radio signals can be transmitted from beacons whose global positioning system position is well-established, to supplement global positioning system signals in areas of poor or no signal coverage.

In a preferred embodiment, the data logger further comprises monitoring means for transmitting to a central controller at intervals during use of the data logger, data relating to one or more of: the identity of a user of the data logger, the position of the data logger, direction and speed of movement of the data logger, and time expired since last user interaction with the data logger. In this way, a central controller can monitor the progress of an inspection.

Preferably, the monitoring means further comprises means for transmitting an alarm signal to the controller if any of the above mentioned data falls outwith predetermined values. This is a useful safety mechanism, which can be used to raise the alarm if the user of the data logger has met with an accident and is unable to use the data logger.

Preferably, the data logger further comprises additional alarm means which send an alarm signal to the controller at the user's behest. The user can hence send his own alarm signal if he requires assistance whilst performing an inspection.

Advantageously, the monitoring means further comprises alarm means which raises an alarm for the user if no data has been received from the controller for a predetermined time period. This alerts the user to a possible problem at the central controller.

In a preferred embodiment, the data logger comprises two modules, being a global positioning system module housing the non-differential global positioning unit, an antenna and circuitry, and a user interface module housing the central processing unit, the display screen, the data entry means and the data storage means. Preferably the data entry means is a keyboard. Advantageously, the global positioning system module is removably mountable on the user interface module. The global positioning module can therefore be used with a further user interface module when

the first user interface module is not being used for an inspection, such as when data is being exchanged with the central controller.

A global positioning apparatus and data logger according to the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 shows a schematic block diagram of a modular data logger according to the present invention; Figure 2 shows a flow chart illustrating the operation of global positioning apparatus included in the data logger of Figure 1; Figure 3 shows a flow chart illustrating a calibration program used in the data logger of Figure 1; and Figure 4 shows a flow chart illustrating part of the operation of the data logger of Figure 1.

Figure 1 shows a data logger 10 comprising a global positioning module 12 and a user interface module 14. The global positioning module 12 comprises, within a housing, an active antenna 16 and a receiver 18, for receiving global positioning system (GPS) signals, and a circuit board 20 for control of the module 12. The global positioning module 12 is a so-called"Galium"module, which uses a commercially available non-differential global positioning system receiver. Alternative modules based on non-differential global positioning systems could also be used, but an advantage of the Galium module its ability to utilise a

range of receivers 18, so that the module can be used with more than one GPS signal network. The global positioning module 12 also comprises means for measuring the speed and direction of movement of the module (not shown).

The user interface module 14 comprises, within a housing, a central processing unit 26, random access memory 24, data storage means in the form of solid state disk storage 28, a touch-sensitive display screen 30, data entry means in the form of a keyboard 32, and two data interfaces 22,23. The first data interface 22 is for the download and upload of data to and from one or more central controller systems, both remotely and via a physical connection. These components are joined together in the known manner. The second data interface 23 is provided between the global positioning module 12 and the user interface module 14 so that data and other signals can pass between the two, also in the known manner. The central processor unit 26 and other electronics contained within the modules 12,14 perform a number of different functions, as will be described in due course.

The two modules 12,14 are configured as separate units which are plugged together for use. This allows, for example, a global positioning module 12 to be used with a different user interface module 14 whilst previously logged data is being uploaded from the first user interface module 14. However, alternative constructions are possible, such as

containing all the components in a single housing, or dispersing the components between two or more plug-together modules, depending on the requirements of the user.

The data logger is primarily for use in inspection and maintenance of infrastructure systems, such as railways, roads, power cabling and water supplies, and any other infrastructure which is geographically diverse and requires regular inspections for the purpose of logging defects and work needing to be done. In the discussion which follows, it is assumed that the data logger is intended for use with a railway infrastructure.

Operators of such infrastructures maintain maps of the network, and inspectors are sent out to check sections of the network. The results of the inspection are logged and include information relating to the general state of the section, any repairs which need to be made, whether previous repairs have been made, and other work needing to be done, such as the removal of rubbish, and other general maintenance.

The data logger is in effect a handset which is used in conjunction with a central database and controller, which may be, for example, an Oracle database. The database contains detailed information about the entire infrastructure, including highly precise GPS measurements of particular features of the network. This enables an electronic map of the infrastructure to be generated, which

is precisely located within the world co-ordinate space as measured by GPS. All features of the infrastructure can be included on the map, and the location of repairs and work to be done can be added to the map, and deleted when the work is completed.

Before use, the data logger 10 is loaded with information describing the section of the network which the user is due to inspect or work on. This is done by connecting the data logger 10 to the central database by means of the interface 22, either directly or via a networked computer in communication with the database.

Sufficient information is provided to give a detailed map of the relevant section.

Once the user reaches the relevant section, operation of the GPS system is commenced. The data logger 10 tracks its own position at all times during use. Also, the speed and direction measurement means is continually operational.

Generally, a GPS signal will be available, which is picked up by the antenna 16 and processed by the receiver 18 and circuitry 20. The resultant GPS position is fed to the central processing unit 26. However, differential GPS coverage can be patchy, or the user could be required to go out of range of the signal, for example, during inspection of a tunnel. It is vital that an accurate GPS position is recorded at all times so that all logged information has a corresponding accurate position which allows the

infrastructure map to be as accurate as possible, so that maintenance can be efficiently carried out.

Therefore, the central processing unit (CPU) 26 is provided with a position algorithm to calculate the GPS position during periods of poor or no GPS coverage. The CPU 26 interrogates the global positioning module for a GPS position, and one will be provided if a GPS signal is available. If there is no adequate signal, no position will be supplied. At this point, the position algorithm operates.

It takes the most recent measured GPS position, and also the speed and direction of movement measurements measured by the global positioning module. The speed and direction, together with the time elapsed since the last GPS position was measured, allow the algorithm to calculate a likely current position, so that it can provide a predicted GPS position in place of a measured GPS position.

To avoid significant errors in the prediction, and hence significant errors in the infrastructure map, the algorithm only functions during a predetermined prediction period. If too long a period elapses since the last measured GPS position, the predicted position become unacceptably inaccurate, so if the prediction period expires before a GPS signal is again received, an error message is returned to warn the user that any position predicted will be invalid, and hence any data logged will not appear correctly on the infrastructure map.

This process is illustrated in terms of a flow chart, shown in Figure 2. The CPU 26 attempts to obtain a GPS position from the global positioning module 12 and also determines from it the latest readings of direction and speed of movement (Box 34). The CPU 26 then determines whether a GPS position was actually available (Box 36). If yes, this GPS position is used as the actual position of the data logger 10 (Box 38), and the process of tracking the data logger's position returns to the start, with the CPU 26 attempting to obtain the next GPS position from the global positioning module 12 (Box 34). If no, the CPU 26 checks whether the length of time since the last reading of the GPS position is within the prediction period (Box 40). If yes, the CPU 26 uses the position algorithm to predict the position, and this predicted position is used as the actual position of the data logger 10 (Box 42). The tracking process then begins again (Box 34). If no, the position status of the data logger 10 is determined to be invalid (Box 44), and the tracking process starts again (Box 34) as the CPU 26 attempts to obtain a GPS position from the global positioning module 12.

Thus, at all times, the data logger 10 either has an accurate measured GPS position, or has an acceptably accurate predicted GPS position, or"knows"that its position cannot be accurately predicted.

For maximum accuracy, it is necessary to calibrate the infrastructure map data in the GPS world co-ordinate space. The infrastructure map contains highly accurate GPS position data, but not at all points, so there may be inaccuracies in position data at areas between these points. The CPU 26 is therefore provided with a calibration program.

Once the data logger 10 has obtained a GPS position at the start of the inspection, a map of part of the network in the region of that position is displayed to the user on the touch-sensitive screen 30. The user is then required to move to a feature shown on the map, such as a marker post or a bridge, and once there, touches the screen 30 at the relevant feature, so tell the data logger 10, in effect,"we are here". The position of the touch on the screen 30 is registered by the CPU 26 in the known manner, and converted to a location on the infrastructure map. The calibration program compares the actual measured GPS position with the GPS position for that location incorporated within the map data, and in the event of any discrepancy, derives a calibration factor to convert between the two. This calibration factor can be applied to any subsequently measured GPS position to that data logged at that position can be accurately incorporated onto the electronic map.

The operation of the calibration program is depicted as a flow chart in Figure 3. The touch sensitive screen 30 displays a map on an estimated position obtained from the

position tracking process shown in Figure 2 (Box 46). The user then indicates to the data logger that he wishes to calibrate it, by selecting a"position fix"option, and then touches the screen at the feature on the map which represents the position at which user and data logger are located. The CPU returns a GPS position corresponding to that location, according to a process which will be described shortly (Box 48). Finally, the CPU calculates and returns a GPS calibration, or compensation, factor, to be applied to GPS position readings (Box 50).

Once calibration has been achieved, and the GPS position tracking is operational, the user can start the inspection. Using the map, and other relevant information about the infrastructure which can be displayed on the screen, to navigate the inspection area, the user can use the keyboard 32 or the touch sensitive screen 30 to enter data relating, for example, to any repairs or work which he sees need to be done, and the data logger 10 will store that data, in the data storage means 28, together with the GPS position, either measured or predicted. Thus, each piece of stored data has a corresponding position measurement, so that it can be accurately incorporated onto the electronic map. Zoom settings and scroll facilities can be provided to enable to the user to view the map more conveniently, as is well-known for computer display monitors.

A procedure for deriving the position of a feature to which logged data relates is as follows. The CPU 26 determines the data logger GPS position according to the process shown in Figure 2, and applies any calibration factor derived from the process shown in Figure 3. From the calibrated GPS position, the relevant area of the electronic map is selected, and the boundaries of the relevant area calculated. According to the size of the screen, and any "zoom"setting the user has selected to see the map in more detail, the boundaries are converted to screen boundaries so that the correct portion of the map, at the correct scale, is then displayed on the screen 30, with the present position of the data logger 10 indicated. Each pixel of the map display is allocated a position which relates to the GPS position of the feature of the infrastructure depicted by that pixel. If no touch on the touch sensitive screen 30 is detected, the process repeats so that the map updates as the user moves around the inspection area.

However, if the user reaches the vicinity of some feature or defect about which data needs to be logged, and this point is not the current reported GPS position, he touches the screen 30 at the point where the feature or location of the defect is depicted on the map. The touch is detected, and the pixel position at the position of the touch is obtained. The CPU 26 then converts the pixel position to the GPS position, in the reverse of the process

used to display the map in the first place. The GPS position can then be stored by the data storage means 28, and the user can enter data describing the defect, for example, which is stored together with the GPS position.

Figure 4 shows a flow chart illustrating this procedure. A GPS position is obtained, via the process shown in Figure 2 (Box 52). Then, the calibration/compensation factor obtained via the process shown in Figure 3 is applied (Box 54). Next, the GPS position and any user"zoom"setting are used to calculate so-called"world co-ordinate bounds" (the co-ordinates of the relevant part of the map), which are converted to so-called"screen bounds"or pixel positions, so that each pixel on the touch sensitive screen has a value assigned to it according to the position, or part of the map, which it is to display (Box 56). A map corresponding to the derived GPS position is then plotted, or displayed, on the screen, showing local features of the infrastructure (Box 56). At this point in the process, the CPU checks to see if the user has touched the screen (Box 60). If no, the procedure returns to the start (Box 52) so that the displayed map can be updated. If yes, the CPU obtains the pixel position at which the screen was touched (Box 62). The CPU next converts that pixel position to an estimated GPS position by scaling the screen bounds for the pixel position back to the world co-ordinate bounds (Box 64), and then returns a predicted GPS position for the point

on the map represented by the screen position which was touched by the user (Box 66). After the value is returned, the procedure restarts from the beginning (Box 66) to update the map display.

Once the inspection is completed, the data logger 10 is once again connected to the central database or networked computer, via the first data link 22, and the stored data with its corresponding GPS positions, is uploaded to the database. It is immediately incorporated into the data describing the infrastructure, so that the next download of data by a data logger 10 will provide a fully up-to-date map. In this way, data stored in the data logger 10 from a number of inspections can be uploaded in a single batch, for example on a daily basis.

Alternatively, the remote data link provided by the first data interface 22 can be utilised to upload the data to the database immediately it is entered into the data logger 10. This allows for the infrastructure map to be updated instantaneously.

The data logger can also be used by those going out to make repairs and do maintenance, as it provides them with an accurate map of where they should be working, and the GPS position tracking will indicate when they have reached the correct location.

A number of additional features can be added to the data logger, together or in combination.

As described above, in areas of poor or no GPS signals, the data logger can predict its GPS position for a short period of time after receiving a GPS signal, by making calculations based on measurements of time, speed and direction of movement. However, these predictions become increasingly inaccurate over time until eventually they too unreliable to use. In some situations, though, the data logger can be out of range of a good GPS signal for a significant period of time. This occurs, for instance, if a prolonged inspection is being carried out in a tunnel.

To overcome this problem, it is possible to provide the data logger with means for receiving radio frequency signals. The signals are emitted from specially erected beacons, and contain encoded information giving the exact GPS position of the beacons. The CPU of the data logger can decode this positional information and extrapolate to calculate its own GPS position, so that an appropriate map can be displayed and correct positions of logged data can be recorded.

Additional database information can be entered into the data logger which allows the user to access predicted, precalculated GPS positions for particular locations by entering a known reference name or code for that location.

This allows the user to obtain GPS positions for locations remote from his present location.

A monitoring and alarm system can be provided for the data logger, which can serve a number of advantageous functions. Monitoring means, which in the case of the data logger of Figure 1 is a so-called"short message service" module associated with the Galium GPS device. The monitoring means regularly transmits a signal to a central controller, which may be, for instance, a local control room, or alternatively could be the central database. The signal carries information about the user of the data logger (who can be required to"log-in"to the data logger before use, in a conventional manner), its GPS position (measured or predicted), the speed and direction of movement as measured by the global positioning module, and the length of time since the user last interacted with the module. The signal is received and monitored by the controller, and an alarm is raised by the controller if any of this information deviates from a predetermined norm. For example, if no user interaction has occurred for a long time, or if the unit has stopped moving unexpectedly, the user could have sustained an accident, so a message can be sent to an appropriate source of assistance, for example, to other users in the same area. Alternatively, lack of user interaction could indicate that the user has forgotten to turn off the data logger, so an alarm message could be sent to him reminding him to this.

Similarly, the transmission feature of the monitoring means can be used to allow the user to send an alarm signal direct to the controller in case of difficulty. Also, the monitoring means can be arranged to raise an alarm to the user if any expected communication from the controller to the data logger is not received in a given time period. In this way, the data logger is made fail-safe, as the user is made aware that something is amiss with the system as a whole.

Claims

Claims 1. A global positioning apparatus for use in a data logger for logging data relating to infrastructure systems, comprising a global positioning unit which, in use, measures the global positioning system position of the apparatus, means for measuring the speed and direction of travel of the apparatus, the unit and the means both being in data communication with a central processing unit which is provided with a position algorithm which, in use, predicts the global positioning system position of the apparatus from an earlier measured global positioning system position and the measurements of speed and direction of travel of the apparatus.
2. A global positioning apparatus according to claim 1, in which the global positioning unit is non-differential.
3. A global positioning apparatus according to Claim 1 or Claim 2, in which the position algorithm is arranged such that if a predetermined time period has elapsed since a global positioning signal was received, the algorithm returns a message to inform the user that no valid position can be calculated.
4. A data logger for logging data relating to infrastructure systems, comprising a global positioning apparatus according to any one of claims 1 to 3, and user interface apparatus, the central processor unit of the global positioning apparatus further being provided

with means for transmitting and receiving global positioning system positions and data relating to the infrastructure system to/from a central controller, and the user interface apparatus comprising means for entering data, and a display screen for displaying global positioning system positions, infrastructure data and entered data.
5. A data logger according to Claim 4, in which the global positioning system positions and infrastructure data are combined and displayed in the form of a map of the infrastructure.
6. A data logger according to Claim 4 or Claim 5, in which the display screen is touch-sensitive.
7. A data logger according to Claim 6 read appendant to Claim 5, in which the central processor unit is provided with a program for measuring the on-screen position of a touch on the touch sensitive screen, and software which relates the measured on-screen position to the infrastructure data to generate a location within the infrastructure map.
8. A data logger according to Claims 5 to 7 when read appendant to Claim 5, in which the central processor unit is further provided with a calibration program which can compare a global positioning system position with a generated map location to produce a calibration factor, the factor then being applicable to subsequent

generated map locations to convert generated map locations to global positioning systems positions.
9. A data logger according to any one of Claims 4 to 8, which further comprises data storage means for storing entered data and the global positioning system position at which data was entered. The stored data can be fed to the central controller after the inspection.
10. A data logger according to any one of Claims 4 to 9, which further comprises means for receiving radio frequency signals carrying positional information relating to infrastructure features.
11. A data logger according to anyone of Claims 4 to 10, which further comprises monitoring means for transmitting to a central controller at intervals during use of the data logger, data relating to one or more of : the identity of a user of the data logger, the position of the data logger, direction and speed of movement of the data logger, and time expired since last user interaction with the data logger.
12. A data logger according to any one of Claims 4 to 11, which further comprises means for transmitting an alarm signal to the controller if any predetermined data falls outwith predetermined values.
13. A data logger according to any one of Claims 4 to 12, which further comprises additional alarm means which

send an alarm signal to the controller at the user's behest.
14. A data logger according to any one of 11 to 13 read appendant to Claim 11, in which the monitoring means further comprises alarm means which raises an alarm for the user if no data has been received from the controller for a predetermined time period.
15. A data logger according to any one of Claims 4 to 14, in which the data logger comprises two modules, being a global positioning system module housing the non differential global positioning unit, an antenna and circuitry, and a user interface module housing the central processing unit, the display screen, the data entry means and the data storage means.
16. A data logger according to any one of Claims 4 to 15, in which the data entry means is a keyboard.
17. A data logger according to any one of Claims 4 to 16, in which the global positioning system module is removably mountable on the user interface module.
18. A global posting apparatus substantially as described herein with reference to the accompanying drawings.
19. A data logger substantially as described herein with referenceto the accompanying drawings.