Research On The Optimization Of DGPS-assisted Low-altitude Photogrammetric Control Point Layout

The traditional operation mode of low altitude unmanned aerial vehicle photogrammetry requires a large number of control points to carry out the internal work,such as the aerial triangulation.The combination of the Differential Global Position System(DGPS)technology and the low altitude photogrammetry technology has effectively changed the operating mode.The new system can directly acquire the exterior orientation elements of the image,and use it as the weighted observation value of the adjustment of the regional network for joint adjustment,so as to improve the accuracy of the exterior orientation elements.What’s more the system only needs a small number of control points can be carried out aerial triangulation calculation,so as to shorten the period of mapping.The emergence of DGPS technology,not only has realized the reduce dependence on the control points during image processing,but also solved the problems in the deathtrap to carry out mapping,and also can achieve drawing rapidly and product various types of digital map products.Therefore,DGPS assisted low altitude unmanned aerial vehicle photogrammetry can meet the needs of rapid updating geographic information and has a very broad development prospect.At present,low altitude photogrammetry aided by DGPS has been realized that in the case of no control point,a DOM of a scale of 1:500 is successfully made in plain area.But in hilly area and even mountainous area,we cannot achieve large-scale mapping without control points.Only when accuracy meets the requirements,can we reduce the control points as much as possible.In this paper,experiments were carried out in the hilly area in order to verify make the DGPS technology used to assist low altitude UAV photogrammetry,the number of control points can be reduced when the accuracy meets the requirements.The following research has done in this paper.(1)The basic principle and mathematical basis of DGPS assisted low altitude unmanned aerial vehicle photogrammetry technology are studied.(2)The error source and error correction method of low altitude unmanned aerial vehicle photogrammetry with the aid of DGPS are analyzed.(3)This paper analyzes how to correct image aberration in the process of generating digital orthophoto map,and introduces the principles and methods of image denoising,image matching,image fusion and image mosaicing.(4)Study in hilly areas,By combining the DGPS technique with the low altitude unmanned aerial vehicle photogrammetry,realized Reducing control points and set up nine different control points layout schemeare.Then,the accuracy evaluation and time efficiency evaluation are carried out for the Digital Orthophoto Map under each scheme,and then an optimal layout scheme is sought.The data is calculated by DGPS assisted low altitude photogrammetry,While meeting the requirements of the mapping precision,the number of control points is reduced by 83%,and the time is saved by 73%.while making a Digital Orthophoto Map of a scale of 1:1000 in the hilly terrain.This is of great significance for practical engineering projects,while ensuring the accuracy of the results,and at the same time,reducing the field workload and improving the work efficiency to a large extent.