Other practical problems of a CCD based system like data storage and field of view were also considered during the design phase. Accurate centroid location of the target points was done by least squares based template matching which provided a precision of 0.03 pixel for the images of these laser dots. The main idea was to obtain high precision image co-ordinates of the actively placed target points and combine them with known projector orientation for automated high accuracy object space measurement. After an analysis of the key problems of the projection system, a diffraction grating based diode laser dot matrix was selected to place a large number of high contrast discrete target points on the object. Using active triangulation as an approach towards this measurement goal, this thesis describes the concept behind and the work carried out for the design of an automated system to measure the surface of massive sandstone strata. These problems increase further for a featureless and low texture object like massive sandstone strata. CCD based active triangulation for automatic close range monitoring of rock movement.ĭoctoral thesis (Ph.D), UCL (University College London).Īutomatic close range photogrammetric measurements face a number of difficulties due to depth of field and lack of sufficient texture in high resolution images at close range.
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