Abstract: In this paper, we transferred the normal height of ALOS AW3D30 to GNSS ellipsoidal height based on the EGM96, and analyzed the precision of this digital elevation model in the northeastern Qinghai—Xizang Plateau (QXP) combining with the ground GNSS measurements. We also calculated the gravitational free air anomalies in the northeastern QXP based on the campaign gravity measurements, and evaluated the precision of the EIGEN-6C4 gravitational mode. The results showed that the standard deviation of the difference between ALOS AW3D30 and GNSS results is 3.4 m, which demonstrated that the precision of the ALOS AW3D30 in this region was better than 4 m. The measured gravity anomalies showed generally negative with local positive values, ranging from -177×10^-5 to 166×10^-5 m·s^-2. The modeled gravity free air anomalies of the EIGEN-6C4 changed from -163×10^-5 to 142×10^-5 m·s^-2. The difference between the EIGEN-6C4 gravity anomalies and measured results span from -119×10^-5 to 63×10^-5 m·s^-2, which indicated that the EIGEN-6C4 gravity anomalies were poorly constrained in the northeastern QXP and the measured gravity anomalies should be combined when analyzing gravity anomalies in this region. At last, we fused the EIGEN-6C4 modeled gravity anomalies with the measured ones by the “remove-restore” method, and improved the precision of gravity free air anomalies in the northeastern QXP, especially around the eastern Qilian— Haiyuan Fault and its surrounding areas. The improved regional gravity anomalies can provide a reference for the study of gravity field in the northeastern QXP.

Key words: ALOS AW3D30, GNSS, the northeastern Qinghai—Xizang Plateau, Campaign gravity, Gravity anomalies