High-Speed Measurement of Tunnel Front faces with a CCD Camera

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The former of the year 1991 was devoted to the research works : "Target Detection for CCD Camera Calibration" and "Design and Development of the ON-line CAD for Ground Surveying". These were originally scheduled to have been done earlier. The latter half of the year was used for making reports. The research results are as follows :(1) Target Detection--- For CCD camera calibration we have to use special targets because the pixel sizes of CCD cameras are relatively large. We employed spherical targets so that they are imaged to circles whatever directions they are sighted in. But since the very sensitive illumination is required to get true circle images, we could not obtain practical measurement precision.(2) Development of the CAD system--- The essence of digital platters is CAD with which all devices and survey works are controls. We developed a CAD system to depict figures on-line at survey sites. Sinice digital plotters are now still immature for practice, we linked this to a total station and published the whole system as "CAD-Based Plane Table Surveying System".