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Development of a Low-Cost DGPS/DR System for Vehicle Tracking 
1 1 2 
Xiufeng He , Thor I. Fossen and Yongqi Chen 
Department of Engineering Cybernetics 
Norwegian University of Science and Technology, N-7034 Trondheim, Norway 
E-mail: xfhe@itk.ntnu.no and tif@itk.ntnu.no 
2 
Department of Land Surveying and Geo-Informatics 
The Hong Kong Polytechnic University, Kowloon, Hong Kong 
E-mail: lsypchen@polyu.edu.hk 
Key Words: Kalman Filtering, DGPS, Dead-Reckoning, Filtering, Smoothing. 
ABSTRACT 
This paper presents a low-cost high- 
accuracy integrated Differential Global 
Positioning System (DGPS) and Dead- 
Reckoning (DR) system for navigation. A 
low-cost GPS receiver is used as base 
station, and it is providing the required 
accuracy without the need for a survey 
grade receiver. A real-time algorithm for 
smoothing of the code pseudorange with 
carrier phase measurements is applied. The 
smoothing algorithm provides much better 
positioning accuracy than DGPS alone. 
Since the carrier phase measurements are 
sensitive to cycle slips, a method dealing 
with cycle slips is proposed. Based on the 
smoothing algorithm, a 
computational effective 8-state 
Kalman filter (KF) is derived for the 
integrated DGPS/DR system. For 
tracking applications the proposed 
KF representation reduces the 
computational time with about 50 
percent to the standard KF 
representation. 
1. Introduction 
In general, the land vehicle tracking 
and navigation systems involve 
several techniques like (Driscoll, 
1994, and Coltrin et al., 1994): 
positioning devices to determine the 
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