Gravity-Modeling Considerations in High-Integrity Inertial Systems

Despite the name, accelerometers measure specific force and not acceleration. Since specific force is the vector sum of Newtonian acceleration and the reaction to gravity, the isolation of acceleration from accelerometer measurements requires the determination of the local value of gravity (via software models or databases). Although this process is well understood in the inertial and physical geodesy communities, guaranteeing the integrity of this process for safety-of-life applications requires high-integrity gravity models. This lecture will ‘plumb’ the depths of the topic of gravity compensation in inertial systems. We will explore some of the fascinating, but not widely known, characteristics of the Earth’s gravity field. We will investigate how gravity compensation error can impact inertial navigation performance and we will go through techniques that may be used to model gravity for high integrity, safety-of-life applications such as civil aviation.