An Improved Method for Transforming GPS/INS Attitude to National Map Projection Frame

Global Positioning System/Inertial Navigation System (GPS/INS) integrated navigation systems play a very important role in modern photogrammetry and laser scanning by virtue of their capability of direct measurement of high-precision position and attitude data in the WGS 84 datum. In practice, as georeferencing is often conducted in national coordinates, there is a need to transform GPS/INS data to the required national map projection frame first. This letter presents an improved coordinate-transformation-based method for the GPS/INS attitude transformation by taking the datum scale distortion and the length distortion into account. Experimental results show that the transformation errors of our improved method are on the order of magnitude of 1 × 10^-5°, which can be safely ignored in aerial photogrammetric processing, whereas the maximum error of the previous coordinate-transformation-based method can be up to several 0.001°.