Research On3D Photogrammetry Technique Used In Large Offshore Structures

In the process of semi submersible platform buliding, there are several circumstanceswhere accurate and reliable three dimensional (3D) measurements are required. It is widelyacknowledged that a major asset would be to have a reliable method of obtaining3D modelsbased on refined measurements obtained in a quick and simple way. In the manufacturingprocess of the platform module, the conventional measurement methods are alwaystime consuming, heavy workload, high costs, low accuracy. And it is difficult to meet theneeds of actual production, so we need to develop a new measurement method，which canbe used in the process of semi submersible platform building.According to the theory of binocular vision measurement, we design a photogrammetricthree dimensional modeling system.In this paper, we transplant and applie the theory and techniques of photogrammetry tothe design and construction process of large marine structures. We designed a set of3Dphotogrammetry and rebuilding system.Using the MATLAB Toolbox toolbox_calib, we calibrated the camera of thephotogrammetry system, and we got the internal and external orientation parameters of thecamera, as well as the coefficient of variation of the camera lens distortion.This paper designed a set of coded targets. Using the image processing and signs pointidentification procedures, the coded signs point can be automatically recognized，and we canalso easily get their positioned.Based on the visual measurement of direct linear transformation theory, using theinternal and external orientation parameters got though camera calibration, and the coordinatesystem coordinates of coded sign points got though image processing, this paper calculatedand got the three dimensional space coordinates of the coded sign points.Using image stitching technology, this paper stitched and integrated the coordinates got from sectional measurement, and reconstructed the three dimensional model of the completeobject...