Introduction
Intelligent Transportation Systems (ITS) have become the basic infrastructure for the development of any country. Vehicle Guidance systems, which are a part of these ITS, play a vital role in efficient transfer of men and goods from origin to destination through shortest path with minimum delays and travel times. In the present scenario Guidance Systems are effectively used for many purposes in various fields. Vehicle Guidance Systems are widely in use in many Departments and Organizations. Rail and Road Transportation departments widely use these guidance systems for fleet management and also for public transport. This system guides the users to their destinations by showing the corresponding paths.

In the present scenario traffic problems are increasing in a rapid way. Especially in India, where the travel demand and the travel density are high, traffic is creating many problems. Traffic problems include traffic congestions, traffic jams, delay in travel time, etc. The main causes for this are: the rapid increase in population, non-awareness of traffic rules by the general public, no strict implementation of rules, etc., which, along with many other causes, lead to traffic problems. Especially when the travel is delayed i.e., when the vehicle or the user is unable to reach the destination within a prescribed time, he becomes frustrated, which in turn leads to an inefficient workforce. This hampers the development of the nation. Delay in travel time also increases the mental disorder in the people traveling (Murkami, 2000). This is again a big problem, as it effects people like a slow poison and hampers their mental ability. Delay in travel time mainly depends on two factors. They are - Internal factors
- External factors Internal factors are the factors, which are governed by the user himself like the maintenance of the vehicle, the mode he is traveling, the speed at which he always travels, the road chosen by the user, etc. External factors are the factors, which affect the user externally, like traffic jams, traffic congestion etc. These two kinds of factors are interdependent on each other and cause a mental effect on the user, which is harmful. If travel times are decreased by some means, it creates a positive work-environment. There are many ways of decreasing travel time like by decreasing traffic congestion, by reducing traffic jams, by reducing accidents, etc.

Even after controlling these factors, accidents and traffic jams are inevitable, resulting in traffic problems. If the traveler is informed about the accident or traffic jam before he gets struck in the jam he will be able to choose another path by which he can reach the destination. For this, if he has a data base map, which shows all possible paths between origin and destination, the accident position and the position of the vehicle, then the user can easily judge the alternate paths by which he can reach his destination easily and happily, without frustration. Also if the shortest path between the origin and destination is displayed, the user can use this shortest path to reach his destination fast (Quiroga 2000).

If any person is new to a place and he doesn’t know the route to his destination, but he knows only the name of the destination, then a guidance system will come to his rescue by showing him all possible paths and also the shortest path. The user can then travel using this map and reaches his destination fast and safely. Also if tracking is provided along with display of all possible paths, then the user can view which path he is traveling and he can easily shift between paths, if he is traveling in the wrong direction. The same guidance system can be used by Tourism Department for tourists. Tourists can be guided to their destinations i.e., tourist spots without any manual help, with such type of guidance systems. This gives the tourists an effective and comfortable traveling experience and also attracts many foreign tourists, thus developing the tourism, resulting in inflow of foreign exchange and increase in financial revenues. A GPS-GIS integrated system is most suitable for such vehicle guidance (Taylor et al., 2000).


Fig. 1: All possible paths between Powai and Airport

Global Positioning System
The Global Positioning System (GPS) is a space-based navigation system, consisting of a constellation of 24 satellites, in six orbital planes with 55° inclination to the equator. The satellites are placed at a height of about 20,200 km with 12 hours orbital period and operated by the United States Department of Defense (DOD) for accurate determination of position, velocity and time. All the GPS satellites are controlled by the system tracking stations, ground antenna, and the master control station. 

In each satellite two rubidium and two cesium atomic clocks with stability 1013 to 1014 are used to derive the fundamental frequency fo = 10.23 MHz. The GPS signals are transmitted at two frequencies, designated L1 (154 fo = 1575.42 MHz) and L2 (120 fo =1227.6 MHz), which are derived from the fundamental frequency (fo). Two codes are used, one of which is called C/A (coarse acquisition code, fo/10) and the other is called P (precise, fo) code. As the rate of P code is 10 times the rate of C/A code, its precision is 10 times better than C/A code. The L1 and L2 are modulated by Pseudo Random Noise (PRN) code, (each satellite is identified by this code) and transmitted after biphase modulation with the carrier.

The distance to GPS satellite is estimated by measuring the time a radio signal takes to reach us from the satellite. This is accomplished by cross-correlation of pseudo-random code generated by the satellite and the receiver. The distances from receiver to satellite measured in this way are called code pseudo ranges. Minimum four satellites are required for estimating the coordinates of a point on the Earth’s surface. While the use of the GPS is extensive in defense, navigation and surveying applications, it is also being used in geo-sciences, ionospheric & atmospheric studies, global climate changes, observing polar motion & earth rotation rate, mapping the gravity field, detecting seismo ionospheirc effects, transport and communications, environment management, for accurate time and frequency, etc. (Kulkarni, 2000)

Geographical Inforrmation System
Geographical Information System (GIS) has created a revolution in mapping procedures as it can interact with the features and its attributes effectively (Refer website 3). For the present work TransCAD is used as GIS software. TransCAD is the first and only Geographic Information System (GIS) designed specifically for use by transportation professionals to store, display, manage, and analyze transportation data. TransCAD combines GIS and transportation modeling capabilities in a single integrated platform, providing capabilities that are unmatched by any other package. TransCAD can be used for all modes of transportation, at any scale or level of detail. TransCAD is a state-of-the-art GIS that one can use to create and customize maps, build and maintain geographic data sets, and perform many different types of spatial analysis. TransCAD includes sophisticated GIS features such as polygon overlay, buffering, and geocoding, and has an open system architecture that supports data sharing on local- and wide-area networks. TransCAD extends the traditional GIS data model to include transportation data objects such as:

• Transportation networks
• Matrices
• Routes and route systems
• Linear-referenced data

Page 1 of 2
| Next |