Gravity field estimation from differential GPS (DGPS) and strap down inertial navigation system (SINS) measurements is based on differencing the observed accelerations from both systems. To rotate the specific force accelerations from the INS to the local level frame, accurate attitude information is required. In this study, we demonstrate how uncompensated errors in the gyroscope data from the INS can be corrected using GPS attitude estimates. A simulation study is carried out to investigate how gyro errors affect the gravity estimates, as well as what the accuracy requirements are for the GPS-derived attitude data in order to estimate gyroscope biases. Results show that the GPS attitude data obtained during a flight experiment are accurate enough to correct the gyro data and reduce the effect of attitude errors on gravity estimates to less than 1 mgal.