A Study on Improvement of Error in GPS Standard Positioning Service

Toshiyuki Tanaka, Junichi Takamura

Abstract:	GPS (Global Positioning System) is 3D positioning system using the signal of the satellites. GPS, which is one of the methods of GNSS (Global Navigation Satellite System), has spread as a typical method of positioning system. For example, it is recently used in car navigation system, cell phone and so on. SPS (Standard Positioning System) is a fundamental method in GPS measurement and it has the advantage of simplicity and low-price. Although the precision and accuracy [1] of Differential- GPS (DGPS) and Real-Time Kinematic GPS (RTK-GPS) are better than that of SPS, DGPS and RTK-GPS need complicated and expensive device. SPS is paid attention because of its usefulness and expected that the error will be reduced. Accordingly, we aim at more improvement of error in SPS. We performed the SPS positioning experiments several times at three known points. From the obtained data, we find out two natures of pseudo range error. First, it changes slowly by time. Second, it hardly changes at difference point if the distance is not so far. We propose the error reducing method using pseudo range error. We consider that the pseudo range error calculated at reference point might become compensation factor at unknown point by the characters of pseudo range error. Since this method requires the data that is generally used, it can be applied to the common receivers. Moreover, because of the small amount of calculation, the real-time measurement is possible. We try to correct the actual data using our proposed method. As a result, we obtained the average compensation ratio of 85% concerning with the distance between true position and the average position of the compensated result. Moreover, we obtained the average compensation ratio of 52% concerning with 2drms. Although our method has some restrictions, we think it is valuable by the reason of the common receiver use, the small amount of calculation and the high correction ratio. We focused that the reference point is known. In this case, we consider that we can measure precise position. On the other hand, in the case that the reference point is unknown, we consider that we can measure relative position. We think that it is meaningful for various applications of GPS to measure relative position precisely. Accordingly, we consider that our proposed method is also valuable in those applications.
Published in:	Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004) September 21 - 24, 2004 Long Beach Convention Center Long Beach, CA
Pages:	1902 - 1907
Cite this article:	Tanaka, Toshiyuki, Takamura, Junichi, "A Study on Improvement of Error in GPS Standard Positioning Service," Proceedings of the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2004), Long Beach, CA, September 2004, pp. 1902-1907.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In