Research On Laser Positioning Assisted By Laser Footprint Spot Of Gaofen-7 Satellite

The wide application of spaceborne lidar has greatly improved the efficiency and timeliness of surveying and mapping.The introduction of full-waveform echo data has also improved the lidar's ability to recognize ground objects.The footprint camera carried by the GF-7 satellite records at the same time The precise extraction of the footprint information and the center of mass of the spot is of great practical significance to accurately obtain the laser emission pointing angle and improve the plane accuracy of the domestic satellite laser height measurement.At the same time,the calculation of the laser point ground coordinates through the optical footprint image can be used for the laser altimeter.Provide certain assistance and reference when the environment interference is too large and the positioning is abnormal.This paper uses the laser data of the GF-7 satellite for research.The data is processed by the establishment of a rigorous geometric model,the processing and use of the full waveform echo data,and the centroid extraction of the footprint spot.Part of the laser data in the Beijing area is taken as an example.,Conducted a comparison experiment of using optical footprint images to locate the light spot and directly locate the laser.The main research content and work of this paper are as follows:(1)Summarize and sort out the development process of spaceborne laser ranging system and the current research status at home and abroad,introduce several commonly used spaceborne laser ranging systems,and introduce in detail the GF-7 satellite data used in this article.Features,and establish a rigorous geometric model.At the same time,it introduces and corrects the aberration and atmospheric delay images that have a greater impact on the model,so as to realize the calculation of laser positioning..(2)Combining the footprint image and the echo curve to explain the characteristics of the full waveform echo of the GF-7 satellite,and the relationship between the echo characteristics and the features of the ground feature;a set of processing methods for the full-wave echo of the GF-7 satellite is adopted,Including the removal and smoothing of the waveform background noise,the decomposition and merging of the echo components,and finally select the flat bare ground and the laser footprint point of only one building,and use the echo ranging data to determine the height of the building Perform extraction and verification;(3)Aiming at the characteristics of the laser footprint of the GF-7 satellite,a new method is proposed to extract the centroid of the surveillance spot and an image matching method based on the principle of least squares to extract the centroid of the footprint.Through experiments and summaries of a series of data,it is proved that these two methods improve the extraction accuracy of monitoring spot and footprint spot centroid respectively,and prove the stability of GF-7 footprint spot and the laser footprint and optical footprint.The geometric stability of the printed image proves that the laser spot positioning can be performed through the optical footprint image,thereby providing a certain auxiliary and reference role for the laser positioning,and applying it to the verification of the positioning accuracy of the laser data points in the Beijing area.