Research On Image-free Control Method Of UAV Image Supported By City CORS

The accuracy of the original onboard POS data of the UAV is difficult to meet the high-precision direct geolocation requirements in the positioning process.If the ground image control point auxiliary image is not used,the accuracy of the model is very different.In order to be able to directly utilize airborne POS data image processing in the UAV surveying and mapping industry,it eliminates the need for relying on ground image control points,reducing the consumption of manpower and resources,and meeting the high-precision geographic information products needed for smart city construction more quickly and efficiently.It is of great scientific significance and practical value to study the POS positioning and positioning optimization method based on ground GNSS CORS.This paper selects the production of aerial survey results in Xuzhou City as an example.The main research contents include:(1)For the UAV POS solution,the city’s CORS benchmark network can be fully utilized to select GNSS reference stations within and around the survey area,including China University of Mining and Technology(CUMT),Liguo(LGUO),Dawu(DAWU),and Sanbao.Six CORS reference stations(SANP),Shuanggou(SGOU)and Zhengji(ZHJI)were used for quality analysis.The results show that the relative error of the baseline calculated by Dawu and Liguo as control points is 0.02 ppm and 0.03 ppm,the root mean square error is about 1 cm,and the point accuracy is better than 1 mm.The Sanbao is the control point.The baseline relative error of the calculated CUMT site is less than 0.15 ppm,the root mean square error is also about 1 cm,and the point accuracy is about 1.5 mm.The displacement deviation of each station in the geodetic coordinates is in the centimeter level and does not exceed 6 cm.(2)The GNSS single base station and multi-base station scheme are used to optimize the processing of POS data respectively.The POS data is post-differentially processed according to the stations with different distances from the survey area and different fixed-degree ambiguity.The optimized POS data is subjected to image-free control to establish a three-dimensional model,and the three-dimensional model established under the original POS data,and the three-dimensional model established by the optimized data combined with a small number of image control points are compared and evaluated.The results show that the accuracy of the original POS data is out of the limit of the accuracy of the image processing and can not meet the requirements of the national aerial survey specifications.The error of the POS data image processing plane and elevation after the optimization of the GNSS single base station is 0.635 m and 0.722 m respectively,which can reach 1: 2000 scale national aerial survey specification requirements;GNSS multi-base station optimized POS data image processing plane and elevation errors are 0.515 m,0.489 m,which can meet the requirements of 1:1000 scale national aerial survey specifications;GNSS multi-base station optimized POS combined pole The error of a small number of image-control image processing planes and elevations are 0.083 m and 0.299 m,respectively,which can meet the requirements of image processing of large scale 1:500 national aviation survey gauges.Combined with urban GNSS multi-base stations,the purpose of imagefree drone mapping can be achieved.(3)The study uses two kinds of aerial photography images of aerial photography to perform image processing of all-terrain image control points,and inversely calculates the ideal position of the image,and verifies the feasibility of direct geolocation accuracy of the drone POS.The results show that the plane accuracy is about 0.5m.The need for direct geolocation can be achieved on a flat surface.