CHAPTER 10:  DIFFERENTIAL GPS

10.1  INTRODUCTION

Differential GPS (DGPS) was developed to meet the needs of positioning and

distance measuring applications that required higher accuracies than stand alone

GPS could deliver. A typical differential GPS architecture (see Figure 10 1)

consists of a reference receiver located at a surveyed, known location, and one or

more DGPS user receivers.  The user receivers are often called "mobile" receivers

because they are not confined to a fixed location like the reference receiver.  The

Reference Receiver antenna, differential correction processing system, and data

link equipment (if used) are collectively called the Reference Station.  Both sets of

receivers either collect and store the necessary data for later  processing, or send

them to the desired location in real time via the data link.

Figure 10 1.  Typical Differential System Architecture

This overview outlines some of the fundamental issues of DGPS.  These issues should

be considered by any user considering the need for a positioning system that can give

accuracies better than the absolute PPS or SPS performance.

10 1