Objectives  Improving the accuracy of block adjustment with few or even no ground control points (GCP) is one of the core issues for high-precision mapping of areas difficult to get GCP, and it is also a major technical difficulty. In order to make full use of the footprint image and the excellent high accuracy of elevation, and the high relative accuracy between the laser altimetry data and stereo images, we propose a combined adjustment method of Gaofen-7 (GF-7) satellite stereo images aided with laser altimetry data.

  Methods  In this method, the elevation control points are automatically extracted by registering the laser footprint images and stereo images, and then they are used as the vertical control in the combined adjustment to improve the elevation accuracy.

  Results  The combined block adjustment experiments performed in Shandong with different terrains show that using only laser altimetry data as elevation control, the root mean square errors of elevation can be significantly improved from the original 7.97 m to 0.79 m, and the maximum elevation error is better than 1.5 m.

  Conclusions  The experimental results reveal that the proposed method can substantially improve the elevation accuracy of satellite imagery. Additionally, with integration of few horizontal control points, the plane accuracy and elevation accuracy can be simultaneously improved. The proposed method is of great significance to reduce the field survey and improve the efficiency of block adjustment.