The Practice Of Aerial Photogrammetry Based On UAV And The Studies Of Control Point Layout

Compared to traditional aerial photogrammetric,low-altitude aerial photogrammetric based on UAV and non-measurement digital camera,has various advantages such as low cost,flexibility,high image resolution,and short work cycle.It has been widely used in acquiring geographic information,especially in making large-scale topographic maps.As while,it has some deficiencies,such as small image coverage,large image rotation angle and inclination,unknown interior orientation elements,very bad distortion.Compared with traditional technologies,the data processing and workflow of low-altitude photogrammetric base on UAV has some difference.Due to the lack of accuracy of the POS system,the external azimuth elements and photo attitude parameters obtained by the POS system can only be used to restore the initial topological relationship between the films,and can not be directly applied to the joint adjustment of the drone's low-altitude aerial aerial three-solution.Reasonable placement of image control points is still of great significance to ensure the accuracy of the mapping,improve the efficiency of the operation and reduce the labor intensity of the outside industry.To explore the effects of control point laying on the calculation of the spatial three solutions and to seek the lowest cost control point laying scheme under the premise of achieving the precision required by the specification is of guiding significance to the future production practice.This paper takes the fixed wing unmanned aerial vehicle vertical photography as the research object.Around its mathematical principle and different from the traditional photogrammetry,this paper expounds the key technologies affecting the mapping precision,including low altitude image matching,non measurement digital camera verification,and detailed description of the operation process of UAV aerial photography system,with 17 square meters in Yiling district.As an example,the 1:1000 topographic map is taken as an example to complete the process including route design,image collection,generation of DEM and DOM,and the production of 1:1000 digital line drawing.The survey results conform to the national standard,and the operation flow of the large scale mapping of unmanned aerial vehicles is summarized.Select some of the image data as the research object,design different control points layout scheme and compare the accuracy of results,including the pre flight layout and the comparison of post flight layout schemes,and the comparison of different network layout schemes after flying.It is concluded that the pre flying cloth point and the post flight layout scheme have little influence on the elevation accuracy,but the pre flight layout scheme can obviously improve the accuracy of the aerial triangulation plane.When the number of control points is reached to a certain degree,it is not significant to increase the control point to the air three precision.In the case of a certain number of control points around the guarantee area,we can appropriately reduce the number of internal control points in the area.Through the design of a variety of control points in the same area,the three results are compared,and the rules of the control point set on the aerial survey precision are explored,and the layout scheme of the minimum cost control point under the guaranteed precision is sought.