The IS&S GPS Sensor Unit is a satellite receiver that utilizes the signals coming from Global Positioning System (GPS) satellite constellation and satellite-based augmentation systems (SBAS) such as the USA Wide Area Augmentation System (WAAS). It is a DO-229D compliant GPS-SBAS receiver certified by the FAA for TSO-C145c Class Beta 3.
The primary function of the receiver is to compute the position, velocity of an aircraft and the precise time (PVT). It also computes the integrity of the PVT from the SBAS signal, if available. The receiver detects and excludes failed satellites (FD/FDE) using receiver autonomous integrity monitoring (RAIM) algorithm, whenever there are enough number of tracked satellites. The sensor unit communicates with a host computer through a serial communication link.