Development of the GPS receiver module:
The GPS receiver module constituted the heart of the system. This along with the antenna (figure-4) was developed by the M/s Bharat Electronics Limited.
Each receiver has a facility to store the unique ID and was capable of recording the coordinates of its location every minute (figure-5). A memory module was also added to the receiver, which was capable of storing the recordings of three days. The module was designed so as to draw power from the bus battery. The data recorded from GPS is shown in figure-6. Here the first line indicates the Vehicle ID. Each line indicates a record. In every record, the first entry represents the Latitude-N and the second entry indicate Longitude-E (both in degrees, minutes and seconds), followed by Time (in Hour, Minute and Second) and Date. This data is converted in to degree decimals for further processing.
Development of the software that provides interface between the GPS and the GIS:
The GPS system records the coordinates in a system, which is called the WGS system whereas the maps provided by the ISRO were on the Modified Everest system. Thus the interface of the two required a conversion software which is available as a standard package in the GIS software.
Development of the error correction software:
When the GPS coordinates were plotted on the GIS map of the city it was found that the recordings were not exactly sitting on the roads (figure-7). There were several errors responsible for this. Firstly the resolution of the satellite map was only 20 metres, secondly since digitisation has to be done by manually tracing the satellite image some errors crept in at that stage, thirdly the conversion of coordinates from the WGS to modified everest is not through an exact formula, fourthly the US has given something which is called the selective availability of the GPS signals, the signals
are not 100% accurate. In order to overcome this problem a software was developed which was capable of pulling these coordinates onto the correct road thus facilitating further processing.
Development of the analysis software:
Generation of a log sheet for each schedule was a necessary output in order to find out whether the bus performed punctually as per the schedule. For this purpose the location of the bus was required periodically. The time interval could vary from a minute to half an hour. The GPS module was capable of throwing up this data in terms of the latitude and the longitude, but for a traffic controller who would analyse this data, expecting that he would be able to decipher the coordinates was asking for too much. Therefore on the GIS road map of the city, landmarks were identified at every 200 metres length and a layer was created where the coordinates of all these landmarks were fed (figure-8).
A software was designed which would convert the latitude and the longitude given by the GPS into the nearest landmark and then generate a log-sheet giving the location of the bus at periodic intervals in terms of the landmarks. A sample output is shown below.
Here the first figure in the block gives the kilometer covered from the previous point, the second figure gives the time, and the third word gives the landmark. Also at the end, the distance travelled by the bus in a specified time interval is also indicated.
Another software was developed which would animate the movement of the bus. Once the data was corrected by pulling the locations on the road it was superimposed on the background road map and the software ran a point on the map, which would exactly follow the actual bus movement.
Potential for use
The potential for use of the reports generated was immense. 200 GPS units were mounted on all the buses of a depot. The readings were downloaded every three days and reports were generated. It now became possible to analyse the punctuality of the bus throughout the route. Cases of missed trips and short trips were brought to light immediately. The distance travelled by the bus could now be calculated accurately. Also the maximum speed of the bus could be estimated. It becomes very useful tool for controlling the private buses taken on hire by BMTC. Their billing can be made fully automatic without any chance of wrong billing on account of fake kilometres. The GPS readings could also be the base for scheduling of buses, as now the actual time taken by a bus to cover a given distance was available. The system could also help in case of accidents by establishing the recklessness or otherwise of the driver.
It has been established that the GPS can become a very effective tool for bus transport corporations. The best feature of GPS is that it offers a tool for managerial control at a very low cost. A GPS unit mounted on a bus would cost less than Rs.10,000/- and these prices are falling very rapidly. The system can now be easily upgraded into an online system where the vehicle will be tracked as it moves. Such an online system would be very useful for the recovery vans and the line checking squads. The system developed could very well be used for other transport vehicles.
This project was developed with the financial and technical assistance provided by the Ministry of Information Technology, Government of India. The GPS module was developed by the Bharat Electronics Limited and the analysis software was developed by the BMTC.
- Paper on "Geographical Information System and Fleet Management in an Urban Transport Corporation" by Pradeep Singh Kharola, MD, BMTC, Bipin Gopalkrishna, Director (S&V), BMTC published in the Indian Journal of Transport Management, Volume 23, Number 6, June 1999
- Paper on "Vehicle Tracking through Global positioning System" by Pradeep Singh Kharola, MD, BMTC and Bipin Gopalkrishna, Director (S&V), BMTC, D.C,Prakash, Manager MIS, BMTC, and Nagaraj Ramakrishna, ATM, BMTC published in the Indian Journal of Transport Management, October 2000.