Tip 44: Creating an orthophoto on a non-coordinate plane

Posted on Monday, August 19th, 2013

Tip 44 Video ScreenAn orthophoto is ‘flattened’ photo – an orthographic projection (perspective distortions removed) of photographic data. Orthophotos can be useful in certain applications because they act like maps or drawings – that is, you can do measurement on them (distance and angle).

For PhotoModeler to create an orthophoto, it needs to know the shape of the surface. It uses the 3D geometry of the surface shape and the known/solved orientation of the original photo to remove the perspective distortions.

When the surface is flat the easiest way to create an orthophoto of an area is to use one of the coordinate planes or a plane defined by three points.  A coordinate plane is a plane lined up the the coordinate axes (that is the XY, YZ, or XZ plane). If the PhotoModeler project’s rotation is set up such that the coordinate system lines up with your object (for example the front of a building is parallel to the XZ plane) then it is easy to create an orthophoto of that plane (the building facade).

On the other hand, if the planar surface you need an orthophoto of is not aligned with a coordinate plane, you can pick three 3D points to define the plane. The video shows both methods. You can see a high res version on Youtube as well.


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