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GIS - GPS Integrated system for Call taxi owners - A case study in Besant nagar, South Chennai
Map Digitization and Paperion
Required Map Accuracy
The digital map forms the heart of this real time automatic vehicle location system. The end user is going to monitor the position and the path of his vehicle on this map. The map has to be user friendly and should give important landmarks around the area so that the user knows the ground location of his vehicle. The accuracy of the map is around 3 meters.
The positional accuracy of this map is also a very important factor to consider. This is because of two important reasons. They are:
- The whole objective of the paper is to display the position of the vehicle and hence if the map is not accurate enough, the high precision GPS coordinates would not be of any use. Also, since the coordinates of any vehicle are going to be changing quickly the map should display these changes effectively.
- The communication link of the system is going to introduce certain errors because accurate systems require high costs and infrastructure. Hence, the map needs to be accurate enough to offset the uncertainty in position caused by weak signals.
Considering these factors in mind, it was decided to go for very accurate maps of the study area. The DDP map sheets of CMDA for the Besant Nagar area gave the required accuracy as well as the desired scale that would be suitable for this paper.
Map Scanning and Vectorization
The maps given by the CMDA were A0 size and the first step towards digital map creation is the scanning of the map products. Once the scanning was done, the file was stored in AutoCAD .pcx format.
Next, the Vectorization of the scanned map was done by using the onscreen digitization option present in AutoCAD. Once the whole map was digitized and saved as .dxf format, it was imported to Arc Info software as coverage. Using the edit features of Arc Info, the various node errors were removed and labels were added to denote various roads and streets.
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