Effects of Incorporating Inertial Measurements on the Localization Accuracy of the Seaglider AUV

Seaglider is a buoyancy driven autonomous underwater vehicle (AUV) primarily used as a platform for oceanographic measurements of salinity, temperature, and oxygen, where precise localization is not crucial. A recent experiment tracked a Seaglider, instrumented with an attitude and heading reference system (AHRS), on an acoustic tracking range in an effort to quantify the accuracy of the Seaglider's two localization solutions and determine the effects of incorporating additional inertial measurements into the solution. Preliminary analysis of results has shown the Seaglider's glide slope model (GSM) is more accurate and reliable than the hydrodynammic model (HDM) during typical flight dynamics. Errors in the GSM solution did not exhibit a clear drift behavior but remained on average within 22 m of the ground truth acoustic track over dives with a maximum depth of 90 to 125 m. Errors in the HDM solution exhibited linear growth until the apogee point of the dive when errors began to linearly reduce. On average the error increased at a rate of about 5 m/min between the surface and maximum dive depth, with maximum errors in excess of 100 m during dives with a maximum depth of 90 m. The substitution of attitude estimates from the AHRS into the localization models provided similar but less consistent results with slightly higher errors.