GLOBAL POSITIONING SYSTEM AND POSITIONING METHODS

GLOBAL POSITIONING SYSTEM AND POSITIONING METHODS

Abstract

The Global Positioning System (GPS) has made navigation systems practical for a number of vehicle navigation applications.Today, GPS-based navigation systems can be found in motor vehicles, farming and mining equipment, and a variety of other land-based vehicles (e.g., golf carts and mobile robots). In Section II of this paper, each of these applications is discussed, and the reader is introduced to some of the issues involved with each one. Beginning in Section III, one particular technical aspect of navigation for land vehicles is discussed. Specifically, the research discussed in this paper presents a quantitative examination of the impact that individual navigation sensors have on the performance of a land-vehicle navigation system. A range of navigation sensor performance levels and their influence on vehicle positioning accuracy are examined. Results show that, for a typical navigation system, positioning error is dominated by the accuracy of the position fixes provided by the GPS receiver when GPS position fixes are available and by the rate gyro’s bias drift when GPS position fixes are not available. Furthermore, results show that the accuracy of the GPS position fixes has a significant impact on the relative contributions that each dead-reckoning navigation sensor error makes. The implications of these results for navigation system design and sensor design are discussed.

INTRODUCTION

Global Positioning System (GPS) was developed by the Department of Defense (DOD).
The technologies on which GPS is based were initially tested on three “Timation” satellites with the first launched on 31st May 1967 and other two launched in 1969 and 1974.
The first actual GPS satellite named “Navstar”, was launched by a U.S. Air force (USAF) Atlas centaur booster in February 1978 That satellite, plus the ten after it was designated “Block”, and were built by Rockwell International. They were intended as technology demonstrator and differed from the later operational GPS satellite in that they were placed into orbit with an inclination of 63 degrees not 55 degrees.

An Air Force Delta booster launched the first “Block II” operational satellite on 14th February 1989. Another eight Block II satellites were launched, to be followed by 15 slightly improved “Block II” satellite Block II and Block IIA satellites were also built by Rockwell.

The full 24-satellite operational constellation was finally completed with the launched of a Block IIA satellite on March 1994. The block II/IIA satellites have a design lifetime of over 7 years.