Rigorous Sensor Model of Gaofen-7 Satellite Laser Altimeter Based on Coupled Footprint Camera

Abstract

The Gaofen-7 (GF-7) satellite system adds a footprint camera that shares the same optical path as its laser altimeter to ensure consistent spatial referencing between the laser footprint point and the obtained optical images. However, this introduces additional errors between the two different loads while ensuring the geometric relations of the laser altimeter and footprint camera. First, the accuracy and error analyses of laser altimeter and footprint camera are carried out based on the working mode of the GF-7 satellite laser altimeter and footprint camera in this study. A rigorous sensor model of laser geometric positioning is proposed based on the coupled footprint camera, which is achieved for the geometric correlation of laser spots on the ground and the focal plane of footprint camera. The satellite laser altimeter simulation platform was used to analyses the various error sources on the geometric positioning of the laser altimeter, and GF-7 satellite data were used to verify the proposed geometric positioning model of the laser altimeter and footprint camera. The results show that the positioning error of GF-7 footprint camera is less than 5 m (RMSE) relative to the dual-line array image, which can provide ground control points for stereo mapping.