What is GPS?
GPS stands for Global Positioning System and was originally based on the US satellite system NAVSTAR. There is also a system from Russia called GLONASS. The European Union system is called GALILEO (planned for 2014, with full completion by 2019). China is working on a system called COMPASS (BeiDu-2 Navigation System, planned for 2015, with full completion by 2020).
A GPS sensor receives the following information from satellites orbiting the earth:
- position in x, y and z axes (longitude, latitude, and altitude)
- time (also as coded direct PPS signal)
- number of visible satellites
Some GPS sensors offer additional calculated information like speed. Due to the further development of silicon technology, it is obvious that GPS sensors will deliver more and more information in the future. Modern Inertial Measurement Units (IMUs) fine-tune or interpolate GPS information with additional local sensors like acceleration, gyro, and temperature delivering additional angular data (pitch, slip, yaw) with a higher data rate.
Currently, GPS sensors need a clear view of the sky -- for example,mounted on the roof of a vehicle -- to get the maximum number of satellites.
Logger software can then calculate distance traveled, direction, acceleration and so on based on position data.
GPS is used to precisely calculate latitude and longitude of a specific position. The GPS system is based on a network of many satellites that orbit the Earth twice every 24 hours. The precise orbit of the satellites and their use of very accurate clocks allows precise triangulation of a vehicle's or user's position. Each satellite transmits its exact position and a very accurate time. The accurate time required for GPS is provided to the satellite system by atomic clocks at the U.S. Naval Observatory, thus enabling the complete system to work fully synchronized.