Research And Analysis Of Key Technologies In Low-altitude Photogrammetry System

Along with the rapid development of geographic information industry,especially the rapid progress of sensor technology,wireless communication technology and data processing technology,The traditional ways of operation cannot meet the demand of production.In recent years,unmanned aerial vehicle(UAV)low-altitude photogrammetry with its strong maneuverability,high resolution,low cost,low driving and a series of advantages make up the space(satellite)and aviation remote sensing technology’s some blind spots.It effectively expands the way that people acquire the space of the earth,and greatly improves the efficiency of the acquisition.Therefore,the uav low-altitude photogrammetry system has become a research hotspot in recent years.This paper focuses on the whole process of uav photogrammetry,and combines the reading literature and the uav project got involved in it to meet the actual production needs.The image acquisition and pretreatment of UAV low-altitude photogrammetry system,image matching based on image commander,joint adjustment are studied.The specific research contents of this paper are as follows:(1)The paper discusses the basic knowledge of low-altitude photography and achieved the preprocessing of images,including image distortion correction and image enhancement.The correction of image distortion can avoid the propagation of distortion error and improve the accuracy of image processing.The use of MATLAB programming to complete the image enhancement eliminates interference from different phases and restores the original state of the image.(2)Two basic methods of image matching are discussed,including image matching based on feature and image matching based on grayscale.This paper also introduces the removal method of mismatched points based on RANSAC algorithm.The SIFT algorithm and the least squares algorithm are used to complete the image matching based on the image commander.And the mismatching points will be removed based on RANSAC algorithm after each layer is matched.Based on the analysis of Open-CV,the SIFT algorithm and Herris operator are combined to complete the feature point extraction,and the matching is completed.The RANSAC algorithm is used to eliminate false matching points.test its extractionefficiency,and match accuracy.(3)The paper also summarizes the commonly used analytical aerial triangulation method and comparative analysis,mainly introduces the method of beam area network joint adjustment of aerial triangulation,determine the GPS-IMU data,control points and joins’ the optimal weight ratio by the way of empirically determined weight.And the automatic aerial triangulation process of image has been given.(4)Combining with engineering examples,the whole process of data acquisition and processing of UAV is put into practice.Make sure the best way is used in each link.After comparing and analyzing the accuracy and meets the requirements of the specifications,according to different ground feature types,the digital elevation model(DEM)is edited in different ways.Then the digital orthophoto image(DOM)is edited,including the mosaic processing of the single image,the edit of resulting stitching line and global tilt correction,eventually acquired a 1:1000 high quality digital orthophoto map.