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Image Resection
Example

The following example is given to highlight the most important features of AFIX2.


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This PSP image was obtained in a low speed wind tunnel (25m/s) on a delta wing model. The circular pattern comes from the light source, which was not uniform. Small markers can be seen near the borders of the model. Tools dedicated to recognize circular markers have been implemented in AFIX2. They are called SPOT tools.


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It can be observed in this image that all the markers have been recognized, but other false markers have been found, which are pressure taps. The original markers have to be selected and the pressure taps have to be removed.


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Matching tools have been implemented into AFIX2. They enable to match already identified markers (in the left image) with candidate markers (middle image) obtained with the SPOT tool. The matching tools are very robust and can handle very large marker motion.


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Six parameters are used to define the relative position of the camera and the model. These parameters are three rotations (left part of the dialog) and three translation (right part). They are called external parameters, since they do not depend on the lens itself. The focal distance of the lens is used as an internal parameter.


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A root mean square method is used to identify the six external parameters. The grid is often superimposed in the image in order to help to check the reliability of the parameter recognition. As a result, the world coordinates are known for each pixel in the image. The images can then be used in a quantitative manner.


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Virtual images can be computed according to a virtual location of the camera, as for the image in this figure. The background of the original has been removed because it is not a part of the model. The grid of the model appears in the area that is not viewed in the original image.

Creating virtual images is used to compensate for the model motion during the test. It can be used also to create views that can be helpful to understand the phenomena under interest.

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Overview

Example

Last Update:7 February 2006 - © ONERA 2009 - Terms of use