What Is Gps?

What is GPS?

The Global Positioning System (GPS) is a navigation and precise-positioning tool. Developed by the Department of Defense in 1973, GPS was originally designed to assist soldiers and military vehicles, planes and ships in accurately determining their locations world-wide. Today, the uses of GPS have extended to include both the commercial and scientific worlds. “Commercially, GPS is used as a navigation and positioning tool in airplanes, boats, cars, and for almost all outdoor recreational activities such as hiking, fishing, and kayaking” (www.scign.jpl.nasa.gov).

Three parts make up the Global Positioning System. The first segment of the system consists of 24 satellites, orbiting 20,000 km above the earth in 12-hour circular orbits. What this means is that it takes each satellite 12 hours to make a complete circle around the Earth. In order to make sure that they can be detected from anywhere on the Earth’s surface, the satellites are divided into 6 groups of four. Each group is assigned a different path to follow. This creates six orbital planes which completely surround the earth.

These satellites send radio signals to Earth that contain information about the satellite. Using GPS ground-based receivers, these signals can be detected and used to determine the receivers’. “The radio signals are sent at two different L-band frequencies” (www.scign.jpl.nasa.gov). L-band frequencies refer to a range of frequencies between 390 and 1550 MHz. Within each signal, a coded sequence is sent.

The second part of the GPS system is the ground station, comprised of a receiver and antenna, as well as communication tools to transmit data to the data center. “The omni directional antenna at each site, acting much like a car radio antenna, picks up the satellite signals and transmits them to the site receiver as electric currents” (www.scign.jpl.nasa.gov). The receiver then separates the signals into different channels designated for a...