Integration of INS and GNSS for gravimetric application with UAS

The integration based on Inertial Navigation System (INS) and Global Navigation Satellite System (GNSS) has been successfully developed in observing the gravity. Therefore, this study integrates a navigation-grade INS, iNAV-RQH from iMAR and GNSS from NovAtel to develope an Unmanned Aerial System (UAS) using unmanned helicopter for gravimetric application. The advantages include its good flexibility, and it is an intermediate system between the airborne and terrestrial survey in terms of the coverage and spatial resolution. On the other hand, based on the characteristics of vertical take-off and landing, in addition to the kinematic mode as the measure method in the acquisition of gravimetric results, the Zero Velocity Update (ZUPT) mode is implemented as a novel method with the developed UAS. The preliminary results in kinematic mode show that the internal accuracies of horizontal and vertical gravity disturbance at crossover points are approximately 6-11 mGal and 4 mGal, respectively, with a 0.5-km resolution. As expected, the accuracy in down component is higher than that in horizontal components because the orientation errors could cause large error in horizontal components. Moreover, the repeatability in ZUPT mode is evaluated with accuracies of approximately 2-3 mGal. The capability of developed UAS for gravimetric application has been demonstrated through various scenarios in this study.