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Troubleshooting Rectification Issues

by Technical Evangelist on ‎09-24-2019 01:07 PM (149 Views)

Question

How do I start to troubleshoot when I have a failure in rectification?

Answer

The first attempt should be a “divide and conquer” technique as in math problems. We don’t know where the error is coming from, so we set up a test to determine if the error is in the photogrammetric data or the surface data. In order to set up this test we must change the project elevation (ISAT>Edit Project Settings >Parameter Settings Tab – Ground Elevation) to a known control point or check point that falls on one of the ortho source images. The next step is to remove any surfaces loaded in the OrthoPro project and select the Orthorectification command from the main menu and pick the image that the control point falls on. Select Edit > Properties and set the Void Elevation Coverage parameter to “Use Average Elevation”.  Note: this should show the control point vertical value. Select the Preview Window option at the bottom left of the form and this should pop up a Preview image display. The right click mouse menu allows for a window area around the control point to minimize the processing time. Select the Process button to rectify the image area around the control point. If the point fits pixel perfect, then the photogrammetric solution (IO/EO) is presumed good and the problem is most likely the surface data, or the coordinate system assigned to the surface data. If the control point does not fit, there must be an investigation into the accuracy of the photogrammetric solution.

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