Design And Establishment Of Outdoor Control Field For Non-metric Camera Calibration

Close-range photogrammetry,which is a short distance photogrammetry of various tangible matter and its state of motion.At present,the close-range photogrammetry is almost applied in all areas of national life.In the operation process of close-range photogrammetry,firstly,it needs to photograph the object,and secondly,the photographs are reprocessed to obtain the static and dynamic information of the object.In the photographic stage,the equipment of obtaining images are mainly measuring camera and non-measuring camera.In recent years,with the rapid development of close-range photogrammetry,the application of non-metric cameras,especially the ordinary digital cameras,is a trend to replace measuring cameras to obtain photograph,but non-metric camera is not designed for photogrammetry purposes,its construction is not stable,the inner orientation elements are unknown,lens distortion is large,etc.Therefore,the non-metric cameras must be calibrated in use.The high-precision 3D control field is an reliable reference in the camera calibration.By surveying the control field,it can obtain high precision coordinates of sign points and offer important object coordinates for camera calibration.This paper is supported by the general program of National Natural Science Foundation of China-“Elaborative descriptions on complex structure and quality representing parameters of rock mass based on DCRP(41472243)”.Combining with the research status of 3D control field at home and abroad,the paper designs and establishes an outdoor 3D control field for the purpose of camera calibration.The study includes the design of the sign and the point distribution in the control field,the survey of the control field in the mode of reflectorless total station based on the polar coordinate method,the data pre-processing of the control field survey,the construction of the stable control field coordinate system based on axis alignment,the evaluation of the precision of control field survey based on error theory and the analysis of the factors' influence on the precision.In summary,the paper has made the following research results:(1)The design of 3D outdoor control field.Design the size,shape,color and material of the control field's sign;study and determine the distribution of the points in the control field,arrange 258 sign points which distribute on 12 different vertical surfaces of 2 apartments.(2)The survey of control field based on the polar coordinate method in the mode of reflectorless total station and the data pre-processing of the data.Use the total station Leica TS30 to survey the sign points of the control field based on the spatial polar coordinate method,according to the survey tolerance,revise the initial coordination of the sign points combining with the observed quantity information.(3)The construction of the control field coordinate system based on axis alignment and the transformation of the coordinate.In order to realize the coordinate unification of sign points in each vertical surfaces and evaluate the practical precision in the sign points survey,construct a stable control field coordinate system based on axis alignment and transform the coordinate of the measuring-coordinate system into control field coordinate system to compare and analyze the coordinate of different survey,summarize the selection principle of the points in coordinate transformation.(4)The evaluation of the precision based on error theory and the analysis of the precision influencing factors.Evaluate the precision of the control field survey after coordinate transformation,and the evaluation results are as follows: the theory precision of the control field point survey is ±2mm and the practical precision is ±1.4mm;analyze different coordinate transformation points and the observation condition such as the elevation angle of the sight line(?),the included angle of sight line and the normal line of the sign surface(?)and the slant range(S)towards the precision,and get the conclusion that,the measurers should try the best to keep the ?,?,S,below 20°,50°and 50 m to obtain a high precision in control field survey.In order to calibrate the non-metric camera,this paper designs and establishes a high-precision 3D outdoor control field,offers the scheme of designing the point position,the technical requirement among survey and the methods of data processing in the procedure of establishing the outdoor control field,improves the theory of establishing the outdoor control field in a further move.The study results have important meaning in theory and engineering practice.