Pradeep Singh Kharola1, Bipin Gopalkrishna2, D.C.Prakash3
1MD, 2Director (S&V), 3 Manager (MIS), BMTC
Fleet management is the most important function for any bus based public transport organization. This involves scheduling and planning of routes and at the same time ensuring that the buses run as per the schedule. This becomes exceptionally difficult in bigger cities where the number of buses involved is very high and all these buses perform repetitive trips. The failure of management in ensuring timely operations has resulted in the bus system becoming unpopular and shift in traffic to the personalized modes of transport. . However GPS based Intelligent Transport Systems provide the possibility of monitoring the movement of vehicles at an affordable cost. Presented in this paper is a system, which was evolved by the Bangalore Metropolitan Transport Corporation (BMTC) for tracking of its buses. It has been brought out that an efficient vehicle system would require the integration of two modern technologies viz. the Global Positioning System (GPS) and the Geographical Information System (GIS).
Vehicle Tracking, the essence of fleet Management
Management of a bus fleet essentially involves ensuring timely arrival and despatch of buses. To go a step further it also involves ensuring that the bus touches the enroute points as per schedule. Simple though this may sound, the magnitude of this can be gauged from the fact an Urban Transport Corporation in a city like Bangalore has 2300 buses and about 33000 trips, and these trips pass through repeatedly about 1000 bus stops in the city. In the conventional system some sort of vehicle tracking is carried out manually by posting traffic controllers/timekeepers at some important points. This manual tracking doesn’t give 100% coverage, it totally depends on human alertness and is thus prone to errors, it is very expensive, it is not tamper-proof, and the data generated in the form of entries in the registers do not lend themselves easily for computer processing.
A vehicle tracking system can thus be defined as a system, which enables the fleet operator to find out the location of the vehicle throughout the journey of the vehicle, against time.
Apart from utilising the data generated by the vehicle tracking system for enforcing the schedule of the bus, this data also provides important inputs for decision making. The system facilitates computation of exact distance travelled in a given time span, computation of the speed of the bus at a given location, analysis of the time taken by the bus to cover certain distance and so on. It becomes a very powerful tool in case the Transport Corporations are hiring private buses, as computation of the distance travelled, based on which payments are made becomes totally objective.
Basics of the GPS
Global Positioning System (GPS) has three components namely
- The space segment: consisting of 24 satellites orbiting the Earth at an altitude of 11000 nautical miles.
- The user segment: consisting of a receiver, which is mounted on the unit whose location has to be determined.
- The control segment: consists of various ground stations controlling the satellites.
The system is owned by the US military but they have permitted civilian use of the satellite signals. Each satellite generates radio signals that allow a receiver to estimate the distance between the satellite and the receiver. The receiver then uses these measurements to calculate its own location with reference to Earth in terms of coordinates expressed in latitude and longitude. Thus the receiver continuously records its coordinates at given time intervals. This data, which is continuously recorded, can be stored in a memory module along with the receiver, or it can also be transmitted instantaneously to the central facility. The former would be an off-line system and the latter an on-line system. The off-line system is shown in figure-2.
GIS, the base for GPS:
Geographical Information System (GIS) is a database system for capturing, storing, checking, integrating, manipulating, analysing and displaying data, which are spatially referenced to Earth. In simple words GIS is a computer based software capable of handling maps and various details given on the map. Data generated by the GPS is spatial data referenced to Earth. In other words this data is the coordinates of its own position expressed in latitude and longitude. This data needs to be positioned on a map of the area for any useful analysis. To be more precise a road map of the area, with important landmarks is required. On this map the GPS readings are superimposed for further processing.
Developing the Vehicle Tracking Project: Developing this project involved a multidisciplinary approach, which ranged from mapping the routes upto analyzing the results produced by the GPS. The stage involved in this process were as follows:
- Digitising the road map for the city.
- Developing the GPS receiver module.
- Development of software, which provides interface between the GIS and the GPS.
- Development of the error correction software.
- Development of the analysis software.
Digitising the road map:
The first step of this project was the digitisation of the road map of the city. Though numerous maps were available including the official map published by the Surveyor General of India, these maps were not suitable as the latest roads were not marked on them and moreover an exact map covering the entire area, which is serviced by the city buses was not available. Therefore recourse was made to the satellite images provided by ISRO.
Figure3 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.