The navigation is a critical element of a satellite launcher. The objective of this research is toevaluate the additional precision and robustness provided to the navigation solution by using the reference trajectory data. To include this information, the error state model of a GPSINS configuration is augmented to estimate the difference between the launcher and the reference trajectory attitude data. The assessment of the precision gain is made using the standard deviation of the attitude, velocity and position estimation errors. The robustness is evaluated considering the loss of precision caused by a GPS outage. The velocity estimation is slightly improved, but the attitude estimation greatly benefits from the additional information. Also, the robustness to a GPS outage is greatly improved for all estimated values. The augmented model can withstand errors in the variances of the external perturbations. However, this one could be sensitive to modelling errors.