| Nowadays, Fast collection of three dimensional urban spatial information is a major topic in the field of geodesy and geomatics. With the rapid development of society and infrastructure of modern city, there is a growing requirement for collecting urban spatial information in an efficient, extensive and accurate way. Traditional surveying method based on Total station is labor intensive and inefficient. On the opposite, Mobile Mapping System makes it possible to collect urban spatial information efficiently, extensively and accurately. Some foreign companies (e.g.3D Laser Mapping?Applanix?Riegl) sell their products all over the world, but it is not completely available for domestic demand due to its high price or lack of post-processing software. Therefore, research on the integration of Mobile Mapping System is of great significance.In this paper, the key technique of Mobile Mapping System integration have been deeply researched, including space and time synchronization of multi-sensor system, integrated positioning and orientation of DGPS/INS, vehicle based Stereo Photogrammetry, and vehicle based laser scanning as well as joint calibration of the whole Mobile Mapping System.(1) Space and time synchronization of multi-sensor system. Space and time synchronization is important for multi-sensor integration due to the fact that it is a premise for high-accuracy 3D spatial data collection. The properties of GPS, INS, laser scanner and camera have been analyzed in details in this paper, and a synchronizer based on GPS timing and OCXO crystal oscillator has been researched and developed successfully. The synchronizer can achieve high time accuracy after being synchronized with GPS time system and keep its accuracy for hours during the lack of GPS signal.(2) Integrated positioning and orientation of DGPS/INS and its application in MMS. In traditional photogrammetry, exterior elements are solved based on control points. In Mobile Mapping System, the orientation parameters can be achieved directly by integrated positioning and orientation of DGPS/INS. Many experiments have been profromed to get the positioning and orientation accuracy in different condition. The result is very helpful for applying DGPS/INS effectively in Mobile Mapping System.(3) Vehicle based Stereo Photogrammetry. With several digital cameras installed in the system, sets of stereo camera can be used for stereo measuring on each pair of images. This paper presents the model of realtive and absolute survey for vehicle based Stereo Photogrammetry based on Direct Geo-locating from GPS/INS.(4) Vehicle based laser scanning. As well know, terrestrial laser scanning can capture local 3D spatial data efficiently and accurately. Large scale 3D data collection by integrating laser scanning into MMS can be achieved. And an absolute positioning model has been researched, which can reconstruct the 2D line point cloud into 3D laser point cloud and achieve accurate and efficient 3D spatial data collection.(5) Joint calibration of vehicle based multi-sensors integrated system. With joint calibration, parameters such as principle points?focal length, distortion coefficients of cameras, relative orientation among cameras, relationship of stereo cameras to laser scanner, cameras to IMU and laser scanner to IMU can be achieved. In this paper, the joint calibration Mathematical models has been researched and analyzed. The whole Mobile Mapping System has been calibrated successfully with indoor and out-door high precision control field, and system can achieve a centimeter level accuracy.Based on the reseach of key technique of MMS, the integration of vehicle based multi-sensors system have been achieved in this paper, including integrate positioning and orientation of DGPS/INS, laser scanning system, Stereo Photogrammetry system and panoramic imaging system. The methods of system integration? synchronization?panoramic imaging and joint calibration have been proved to be correct and effective. |
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