Quasi-tightly Coupled GNSS-INS Integration

Abstract

Quasi-tightly coupled integration of Global Navigation Satellite System (GNSS) and inertial navigation system (INS) data is a method of loosely coupled integration that has the salient characteristic of continued aiding with fewer than four satellites that a tightly coupled integration typically exhibits. This method is intended for the integration of an existing GNSS navigation engine into a GNSS-INS closed-loop configuration with little or no modification of the GNSS navigation engine. The method of integration uses the range measurement model matrix typically used to compute dilutions of precision to identify the observable subspace in the time-space frame generated by the available satellites and project the loosely coupled INS–GNSS position measurement into this subspace. The GNSS navigation engine can therefore be any linear estimator. This paper describes the quasi-tightly coupled method applied to a single point positioning least squares adjustment and to a Kalman filter for GNSS position estimation. Copyright © 2015 Institute of Navigation