Study On The Effectiveness Of POS Assisted Low Altitude Photogrammetry In Large Scale Mapping

With the rapid development of the national economy,the geographic information industry is also accelerating the pace of updating.For aerial photogrammetry,the traditional mode of operation has been unable to meet the needs of production,in recent years,the Position and Orientation System has become a hotspot of research in the field of photogrammetry,which is attributed to the rapid development of Global Positioning System(GPS)and Inertial Navigation System(INS),what's more,the POS system combined with them,simplifies the traditional photogrammetric process: no need to set up image control points in the field,according to the position information obtained by the GPS and the attitude information measured by the INS,the external orientation elements of the photograph can be obtained directly,thus it can significantly improve production efficiency and shorten the operation cycle.Therefore,using POS assisted low altitude photogrammetry into large scale mapping can effectively reduce external and internal workload.This paper with the aim of improve the efficiency of POS assisted low altitude photogrammetry,based on the basic theory and principle of photogrammetry and POS,emphatically focuses on the analysis and comparison of the optimal layout scheme of the image control points in different mapping scales,and then put forward the optimization method,in addition,the paper has studied the method of directly generating epipolar image with exterior orientation elements,and explored the effectiveness and feasibility of POS to improve the process of airborne data processing,finally the layout scheme and the method have been verified with actual images and projects,the research contents are as follows:(1)the important links of data processing in digital photogrammetry are expounded,including the conversion of some common coordinate systems,the aerial triangulation,the relative orientation and the absolute orientation process,the digital image matching technology,and the basic principle and mathematical model of each important link are expounded systematically.(2)the basic principle of GPS,INS are discussed,the combination mode of GPS/INS system and the advantages of POS in the application of low altitude photogrammetry in large scale mapping are analyzed.(3)overview of the two operation modes of POS assisted low altitude photogrammetry: Integrated Sensor Orientation method and Direct Georeferencing method.Combined with the experimental project,this paper has designed different layouts of control points,and compared kinds of methods: common aerial triangulation,POS assidted aerial triangulation(integrated sensor orientation method)and Direct Georeferencing method,finally this paper provides the layout of control points for POS assisted low altitude photogrammetry.(4)the implementatin of generating the epipolar images based on the image orientation elements by algorithm based on Visual Studio 2010 platform,and this paper has did the experiment of epipolar image generation utilizing the original data of the POS system and the accurate exterior orientation elements calculated by the aerial triangulation,and the final conclusion is: if the elements of exterior orientation obtained from POS has a high precision,then POS data can be directly used to generate epipolar images to improve production efficiency,or the process of aerial triangulation can't be skipped to gain exterior orientation elements.