Sensor Fusion Based Data Parser of a GPS Receiver for UAV Systems

This paper presents a robust design of a data parser for a GPS receiver targeted for Unmanned Aerial Vehicle (UAV) systems. Typically a GPS receiver periodically outputs NMEA character stream which is subsequently decoded by a data parser. Most often these parsers discard the entire decoded data in case of a checksum mismatch resulting in a data outage. With a sub decimal refresh rate of most GPS receivers, such outages may result in substantial degradation in system performance. Moreover, in an event of a checksum mismatch, it may likely happen that some information in the decoded data may still be valid but could not be retrieved due to the inability of the parser to extract it. In such a scenario, the proposed data parser utilizes the airspeed data from the onboard sensor and attempts to extract the longitude and latitude information from the decoded data packet. The parser algorithm is implemented on a low cost microcontroller platform to form the so called GPS module. Experimental results show that a significant amount of information recovery in events of checksum mismatches was achieved using the proposed algorithm.