Low-altitude Photography Applications Based On DGPS Technology

In the 21st century,the rapid development of economy and society has put forward a higher demand for contemporary mapping services.Thus,fast,accurate and intuitive mapping services are becoming a trend,which makes low-altitude photogrammetry developing from the basis of traditional photogrammetry play a great role.However,the flying platform used in low-altitude photogrammetry can't load too much equipment,so that it can't provide proper condition for installing professional PTZ.Moreover,the images taken by aerial camera generally have small frame,large rotating angle and large distortion difference,which makes the processing of the image data difficult.At the mean time,the model totally dependent on a large number of ground-control points to obtain space coordinates is restricted by ground surroundings.DGPS technology can locate with high accuracy,and applying it to low-altitude photogrammetry is feasible and has economic efficiency.It is most important that this technology can obtain high-accuracy external orientation elements,ensuring the precision of processing of data,It is necessary to study photography at low altitude measurement applications based on DGPS technology.Based on DGPS-supported low-altitude photogrammetry and the current situation of this technology,this paper introduces how it works and its mathematical models,key techniques and the source of error according to its feasibility and practicability of producing.Besides,this paper discusses the working feasibility of afterwards DGPS and real-time DGPS in the area of low-altitude photogrammetry and analyzes the working accuracy,advantages and shortages in production of afterwards DGPS model with the use of ground base stations and DGPS analyzing soft(GGpos).Analyzing above mainly shows afterwards DGPS model can't totally get rid of the control of ground control points.Thus,this paper puts forward a solution to improve this model with real-time DGPS and DGPS-supported low-altitude photogrammetry aimed at the shortages of afterwards DGPS.This paper analyzes the accuracy and efficiency of afterwards DGPS with the help of DGPS-supported fixed wing UAV system to reach the conditions required by some related standards.In addition,it discusses about the accuracy and efficiency of real-time DGPS-supported model when this model is under the condition totally getting rid of ground control points with eBee-RTK UAV system.This paper divides afterwards DGPS and real-time DGPS both into original,improved and ideal conditions,according to thedifferent conditions when two models are used in practice,Postflight Terra 3D and IPS photogrammetry working stations.At last,in application of geological disasters as an example and analysis applications of real-time DGPS assist low altitude photogrammetry.The studies and researches can draw some conclusions.Afterwards DGPS-supported low-altitude photogrammetry can reduce about 50%-80% ground control points compared to the same condition without DGPS.After comparing afterwards and real-time DGPS,the two technologies both satisfy the requirement of tolerance put forward by some national standards and they have the same working performance in the area of accuracy.In the area of efficiency,real-time DGPS doesn't have any superiority in the condition of primitive practice model.While,real-time DGPS model can shorten 30% time cut down 40% cost compared to regular afterwards DGPS with original date processed and real production combined.Combined with the analysis,real-time DGPS assist low altitude photogrammetry in sudden disasters,narrow areas and weak texture region will play an irreplaceable role.