DEVELOPMENT OF REAL TIME WEB BASED DGPS DATA SERVERS

Abstract

Over the years, the Global Positioning System (GPS) has evolved as a Navigational and Positional System and is used widely across the world. The system promises all time positioning information with accuracies if the navigational signals transmitted by the GPS satellites are observed precisely. However several Scientific and Geological surveying applications need the system to provide an accurate positional result in the range of a few millimeters. The Differential GPS (DGPS) technique provides a user with the capability of calculating their position accurate within a few millimeters by using a fixed GPS receiver in addition to the roving one. But again there are several limitations over using DGPS like costlier instruments, distance between rover and base station etc. So applications for which millimeter accuracy is not required but few decimeters will work, web based DGPS server can provide solution as these can provide differential corrections for most of the GPS receivers. This thesis describes a Real Time Web-Based DGPS technique and provides a system design to implement this technique. This will require a base station kept at a known position which can calculate differential correction on its end and provide the corrections to the rover positions. This will be suitable for mobile based GPS receiver in a limited radius of base receiver as well as the regular GPS receiver which can provide pseudoranges to the satellites. With further development in GNSS technologies these algorithms can further be extended for calculating differential correction by using interoperability of different GNSS and can provide accuracies up to millimeter levels for a mobile GPS receiver.