GPS and low cost sensors in navigation

In this paper, we present our work on integrated navigation for low speed vehicles at low altitudes, using Global Positioning Satellites (GPS). The commercial GPS systems are used for determination of speed and location of low speed objects on Earth or airborne objects, with acceptable accuracy. On the other hand, low cost Inertial Navigation System (INS) is suited for similar applications. These systems are self-contained, non-interrupted and do not need external signals. However, GPS errors result in constant drifts in position. These errors in position grow with time, or are unlimited. The INS and GPS systems have complementary characteristics, and hence, can be selected for integrated navigation. To determine the flight position, the INS system operates uninterrupted in an independent mode. Whenever, the GPS system determines the position (usually at lower rate than the INS system), the INS system corrects the speed and position. The commercial GPS systems can not produce the required altitude estimations independently. Therefore, pressure sensor has been used to determine the errors in vertical channel. Kalman filter has been used to integrate all the measurements.