Research and Calibration of Digital Photographic Cameras

Leader of work: Sergij Mogilny, Head of Department of Geoinformatic System and Geodesy

In connection with development of digital technique in phofogrammetric implementations of surveys usually use digital photographic cameras.

The use of digital cameras has a row of advantages:

·popularity;

·possibility of load images in memory of computer

·operative receipt of the coloured images without processing in laboratory;

·possibility of visualization and measuring on the screen of monitor;

·possibility of bringing in of amateurs.

The special digital cameras of high permission that offered for the aims of phofogrammetry are very dear. Therefore it is many cases expedient to use more cheap cameras, allowing to decide many tasks. But such cameras on exactness of results are unable to compete with the special apparatus.

The main problem of the use of inexpensive digital cameras consists in that fact that the elements of internal orientation of images are not permanent and has large distortion. Therefore there is a task of finding of parameters of distortion at calibration. Because, knowing the sizes of errors from distortion, it is possible to exclude them from the results of measuring. [1]

There are two basic methods of implementation of calibration.

1. The first method consists in research of a survey apparatus, it is calibration of cameras.

2. The second method is to determine the size of systematic errors on images. It is calibration of snapshots.

Pictures must be done in those terms in which production photography is executed.

Thus, the calibration of snapshots is the definition of aggregate values in the central projection images corresponding to a survey, and failure points imagery of this projection.

Coming from an accessible equipment for calibration of digital camera for Olympus E20P was chosen method basis in determination of descriptions of central projection of pictures and their distortion is fixed on the pictures of the special ground which the spatial co-ordinates of X,Y,Z of large number of points are certain on.

During conducting of researches thus all actions can be broken up on a few stages:

1. Receipt of snapshots at the survey of tester ground (calibrate stand);

2. Measurement of the got stereo mater;

3. Calculation parameters of calibration;

4. Analysis.

A tester ground is an aggregate of the evenly distributed marks, spatial co-ordinates of which Xg, Yg, Zg is known with exactness 0.1 mm. In all well-aimed 102 things. As a result of conducting of photographing 10 stereo mate were got on every focal distance.

Figure 2.1 Tester ground

For measuring of stereo mate for every value of focal distance the digital photogrammetric station Delta of GeoSystem (Vinnitca).

Further measuring was conducted in a programmatic complex DONETSKFOTO, by the developed Head of Department of Geodesy and Geoinformatic System from National Technical University of Donetsk the professor Sergij Mogilny.

A programmatic complex DONETSKFOTO unites the measured stereo mate to unite in a general fotogrammetric network.

The calculated parameters of systematic errors of pictures are the coefficients of polynomial of the third degree, which approximates systematic distortions of pictures.

For implementation of calculation it is necessary to know focal distance of camera at photographing. They were found the method of selection of values. Focal distance got out such, that error of unit of weight and rejection on supporting points were minimum.

LIST OF REFERENCES

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