Airborne Strapdown Gravity Measurements for Geodesy and Geophysics

The determination of gravity from an airborne platform, commonly known as airborne gravimetry, has been recognised as an operational procedure since the 1990s, using springtype gravimeters mounted on a stabilised platform. Although it has been demonstrated that inertial-grade sensors directly attached to the chassis of the aircraft, i.e. in a strapdown conguration, can have similar accuracy, stabilised-platform systems have remained the predominant method in airborne gravimetry. This is because the long wavelength information in the gravity estimates are contaminated by uncompensated sensor errors, leaking into the gravity estimates. The use of a strapdown gravimeter does however present some appealing practical advantages, since an off-the-shelf Inertial Measurement Unit (IMU), designed for navigation purposes, can be simply installed and used for gravimetry. In collaboration with the Technical University of Darmstadt, the Danish National Space Institute has been operating a strapdown gravimeter on a number of airborne campaigns since 2013. Based on this experience, the strapdown system has gained recognition as an exceptional complement to the stabilised platform system, increasing the operational exibility and resilience against dynamic flight conditions. Additionally, the use of off-line temperature calibration methods has been shown to signicantly constrain the erroneous long wavelength information, promoting the use of strapdown gravimetry as a stand-alone system. The operational exibility and compact size of the strapdown system makes it a feasible candidate for a number of future applications, such as the use in Unmanned Arial Vehicles (UAVs) and surveying marine-terminating glaciers in remote areas of the world. This thesis is a contribution to the development of strapdown airborne gravimetry based on inertial technology. A newly purchased IMU has been own on a number of airborne surveys, demonstrating the feasibility and exibility of using a strapdown system. The different environment of each collected data set is an indication of the superior dynamic range of the IMU-based system, demonstrating the enormous potential for future applications