The Global Positioning System (GPS) is a space-based satellite system that provides information on the position and time for any weather and any place on the face of the earth and its vicinity. You must have an unobstructed direct path with four GPS satellites to obtain valid data.

The data received from the GPS conforms to the standards of communication set up by National Maritime Electronics Association (NMEA) and follows a protocol with different types of sentences. In them, we can find all the information about the position of the receiver. To read more about all the types of NMEA messages, you can visit http://www.gpsinformation.org/dale/nmea.htm.

One of the most interesting pieces of information about a GPS is contained in GGA sentences. They provide the current Fix data with the 3D location of the GPS. An example of this sentence and an explanation of each field are given here:

$GPGGA,123519,4807.038,N,01131.000,E,1,08,0.9,545.4,M,46.9,M,,*47
Where:
     GGA      ...