Research On The Method Of Making Large Scale Topographic Map Based On Oblique Photographic Data

Drawing large scale topographic map is an important part of engineering survey.It has become an important application field of oblique photogrammetry to make large-scale topographic map with oblique photogrammetry data.In this paper,a large number of project production data are selected to study the implementation method and result accuracy of two common tilt photography schemes of single lens multi rotor UAV and vertical takeoff and landing fixed wing UAV equipped with five camera.Different density image control points are selected to process tilt photography data,and the results are compared and analyzed The recommended values of the distance between image control points in two oblique photography schemes are given.The software,hardware and technical process of producing large-scale topographic map based on oblique photography data are sorted out,and the accuracy of topographic map drawn by this method is tested.In this paper,the processing methods of some special cases in making large scale topographic map by oblique photography are explored.In order to provide reference for large-scale topographic survey production.The main conclusions are as follows:(1)Different UAV platforms are equipped with different mission equipment,and large-scale topographic maps with different precision requirements are produced by using tilt photogrammetry method,and the layout schemes of image control points are different.For the inclined photographing scheme of vertical and horizontal CW-10 fixed wing UAV equipped with cw10-wp five lens camera,the aerial height of 1:1000 topographic map should be selected from 300 m to 350 m.For example,the contour distance of mapping is 0.5m,so it is recommended to arrange image control points according to 800 m ~ 1000 m interval.For example,the contour distance is 1.0m,and the distance between image control points can be widened to 1200 m.(2)The method of making large-scale topographic map is that the elevation elements are obtained by using the 3D model data of oblique photography,the plane elements are obtained by using the DOM data of oblique photography,and the contour line generation and topographic map editing and finishing are completed in the South CASS software.The technology is feasible and the accuracy is reliable.After verification,the 1:500 topographic map of a hilly land made by the above method has a mean square error of ± 0.131 m in plane position and ± 0.231 m in elevation of contour line,which meets the requirements of specifications.(3)For the survey area with high surface exposure such as desert and barren mountain,the contour line can be automatically extracted by using the oblique photography DSM data,and the appropriate sampling spacing can reduce the editing workload and improve the production efficiency on the premise of ensuring the accuracy.The true projective image produced by oblique photography has a loss on the expression of thin strip features.The vertical image of oblique photography is processed according to the data of vertical photography,and then the wrong and missed ground objects are drawn by stereo mapping method,which can reduce the workload of field mapping.