Introduction

The Global Positioning System (GPS) is a satellite – based aid to navigation system placed into orbit by the United States Department of Defense.
The system consists of 24 satellites, orbiting the earth twice a day at an altitude of about 12,000 miles.
GPS satellites are powered by solar energy.
Backup batteries are installed on board to keep them running in case of a solar eclipse.
The system provides highly accurate worldwide positioning and navigation information 24 hours a day.