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Land based mobile mapping technology (MMT) can collect spatial and attribute data in high efficiency and the data can meet the requirement of 1:2000 scale or even higher accuracy topographic mapping without ground control point. In mobile mapping, direct georeferencing by the integration of GPS and INS/DR provides the mobile platform's continuous position and pose to mapping sensor in field survey, then image stereo of the certain target is used to calculate its 3d global coordinates. But in general, current MMT image stereo is defined as the solid baseline between the different CCD cameras' relative position deviation which is rigid connected to each other and calibrated by high precise control field, and baseline length is quite short (less than 2 meters). This brings some troubles on the far distance target or big size building observation from different viewpoints, and also limits the use of huge amount of MMT measurable images. This paper presented the image stereo pair construction in soft-baseline condition, which is organized through the different imaging time and platform field place but overlapped to the certain target, thus the baseline's accuracy would be some
obvious lower than the solid one. We made a brief introduction about Tongji Geo-Informatics MMT firstly, analyzed the image stereo pair from the solid-baseline, and then constructed MMT measurable image into soft-baseline stereo and due mathematical model is expressed. In the paper's experiment part, we analyzed the concrete target 3d solution with the total station, MMT image's solid-baseline stereo and the soft-baseline surveying. The calculation shows that the target 3d coordinates solution in soft-baseline has the same precision as the solid one, also meets the topographic mapping
requirement of scale 1:2000. Last, the paper discussed some important influence from the change of angle of two observing bundles in photogrammetric forward intersection and the change sub-deviations of survey error vector in image space coordinate system. As conclusion, MMT soft-baseline brings more choice with target survey in the larger
observing distance and good coordinate solution with the measurable MMT images.
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