ABOUT:

• We are using a combined GPS receiver/antenna unit.
• When turned on, this unit scans for GPS satellites and starts sending data the moment enough satellites have been located. This is also called "getting a fix."
• The indicator LED is steadily lit up while the unit is searching for satellites and is blinking while the unit has a "fix."
• A connector cable is provided with this GPS unit.

GPS COMMUNICATION:

• All GPS devices use the NMEA (National Marine Electronics Association) standard.
• The NMEA standard is a data protocol and a data format.
• The NMEA protocol resembles the Serial data protocol and can be read as is if were serial data.
• The data format is specified here: NMEA (pdf) .
• All the different datasets shown in the NMEA pdf are sent by the device in sequence. Each set provides different information, although some of the information overlaps.
• For our program, we will use the "$GPRMC" dataset.

CONNECTOR CABLE:

we only use three wires of this cable: power, ground, and the serial signal line (tx) that sends data out of the GPS device (and then in our case into the software serial rx line which we have specified as digital pin 2 of the arduino).