In this paper

the use of GSM Short Message method incorporating GPS system vehicle guidance is discussed and a mathematical model is founded to represent the acceleration and main error which affects the GPS/DR integrated system position accuracy.A data fusion algorithm of integrated system is introduced to improve the accuracy of the navigation system.Since the dead reckoning(DR) technique is being used in the system

this algorithm is not only improving the GPS position accuracy but also preventing the error of the DR to be diversified.The method has made the integrated system to be robust and reliable in an environment with a lot of tall buildings

tunnels

bridges and mountains like Hong Kong.