How many GPS satellites are in orbits around Earth?

The space segment currently consists of 28 operational satellites orbiting the earth. They orbit at a height of almost 21,000 km above the earth's surface. Any one satellite completes its orbit in around 12 hours. Due to the rotation of the Earth, a satellite will be at its initial starting position after approximately 24 hours.

How is GPS used?

GPS receivers collect signals from satellites in view. They display the user's position, velocity, and time, as needed for their marine, terrestrial, or aeronautical applications. Some display additional data, such as distance and bearing to selected waypoints or digital charts.

Will GPS receivers work anywhere on Earth?

Yes, GPS receivers can work anywhere on Earth, providing their antennas have a good view to the sky above.

What is NMEA 0183?

NMEA 0183, or NMEA for short, stands for National Marine Electronics Association, a US standards committee that defines data message structure, contents and protocols to allow the GPS receiver to communicate with other pieces of electronic equipment. NMEA 0183 is a standard data communication protocol used by GPS receivers.