Quasi-Tightly-Coupled GNSS-INS Integration

Quasi-tightly-coupled (QTC) GNSS-INS integration is a method of loosely-coupled integration that has the salient characteristics of a tightly-coupled integration. This method is intended for 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 (DOP) to identify the observable subspace in the time-space frame generated by the available satellites and project the loosely-coupled INS-GNSS Kalman filter position measurement into this subspace.