Introduction

Introduction

The Global Positioning System (GPS), also known as the NAVigation Satellite Time And Ranging (NAVSTAR) system had its first satellite launched back in February 1978. GPS is a one-­way radio ranging system which provides real­time knowledge of one’s Position and Velocity, and a very accurate Time reference as well (all together referred to as PVT).

Below are the 4 constellations of GNSS systems:

• Global Positioning System (GPS) - United States
  • Standard Positioning Service (SPS)
  • Precise Positioning Service (PPS)
• GLONASS - Russia
• Galileo - Europe
  • Open service (OS)
  • Public regulated service (PRS)
• Beidou(/Compass) - China

Their properties are:

Figure 1: Properties of GNSS systems