Abstract
For non-metric CCD digital camera features and the needs of Rapid field non-metric cameras calibration, the error sources was detailed analyzed and a mathematical calibration model has been founded. Both detailed multi-image group iterative method for solving DLT coefficient, the elements of interior orientation and distortion parameters of lens and the multi-image resection method for solving the elements of interior orientation, elements of exterior orientation and distortion parameters of lens have been discussed. A standard steel cage (e.g. Figure 1) has been made for real calibrating non-metric cameras outdoor quickly. In order to verify the accuracy, each method mentioned has been used to solve elements of interior orientation and distortion parameters with the same camera (e.g. Figure 2) and the same test images. The results of accuracy show that the maximum X error was 0.2585mm, the maximum Y error was 0.6719mm and the maximum Z error was 0.1319mm by using multi-image DLT algorithm. On the other hand, the maximum X error was 0.1914mm, the maximum Y error was 0.9808mm and the maximum Z error was 0.1453mm by using multi-image resection algorithm. The forward intersection accuracy of the two methods was quite, and the both were less than 1mm. By using multi-image DLT algorithm the planimetric accuracy was less than 0.2585mm and the height accuracy was less than 0.6719mm. On the other hand, by using multi-image resection algorithm the planimetric accuracy was less than 0.1914mm and the height accuracy was less than 0.9808mm. The planimetric accuracy of resection algorithm was the better than DLT algorithm, but the elevation accuracy of DLT algorithm was the better than resection algorithm. In summary both method can be accepted for nonmetric camera calibration. But also the solver accuracy in the inner orientation elements and distortion parameters was not very high has been noted. However for non-metric camera, the true value of inner orientation elements and lens distortion were unknown did not affect the accuracy of photogrammetry.
Highlights
The digital camera is based on the Semiconductor Technology, The Charge Coupled Devices (CCD), which are arrange in a line or a rectangular region square, constitute the imagesensitive linear array or the imagesensitive surface, auxiliary by optical system, mechanical device and electronic circuit's equipment
In the literature that I have seen(HE Min, 2011a)(Miao Hongjie, 2005), in the digital camera calibration, which generally is based on outdoor standardization field or indoor standardization field, we can obtain elements of interior orientation and/or the lens distortion by solute the resection equation or direct linear transformation (DLT) equation
When we solute interior orientation parameters and lens distortion parameters simultaneously in three dimension with multi-Images, we find it difficult
Summary
The digital camera is based on the Semiconductor Technology, The Charge Coupled Devices (CCD), which are arrange in a line or a rectangular region square, constitute the imagesensitive linear array or the imagesensitive surface, auxiliary by optical system, mechanical device and electronic circuit's equipment. Speaking of the digital CCD sensor's character and the sensitivity, it can be stability for a long time. The elements of interior orientation are unknown and the lens distortion is too bigger for normal non-metric digital camera. In the literature that I have seen(HE Min, 2011a)(Miao Hongjie, 2005), in the digital camera calibration, which generally is based on outdoor standardization field or indoor standardization field, we can obtain elements of interior orientation and/or the lens distortion by solute the resection equation or direct linear transformation (DLT) equation. We has founded two mathematical model of the camera calibration, put forward the adoption of the multiimages iteration method to calculate the coefficients of the DLT/resection and distortion parameters in groups by threedimensional ground control points (GCP), The precision of camera calibration are confirmed by the experiments of multiimage resection and forward intersection, and the satisfactory effect is obtained
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