• Home  / 
  • Blog  / 

When I try to add control points to my project, processing fails though it was working properly before.

If you had a project that successfully processed, but after adding control points for the first time it no longer processes properly, the problem is one of incompatible coordinate systems.

When you use PhotoModeler in its normal mode (no control points) an arbitrary coordinate system is set up. (Technically this is a free network datum used to minimize error.) Imported control points will almost always be in a different coordinate system than this arbitrary one. The control points either come from an external survey or from a PhotoModeler dxf export where a scale/rotation has been defined.

The difference in the coordinate system between the control points and the arbitrary internal system can cause grief for PhotoModeler during processing. The basic solution is to make sure that all camera stations are reoriented during the next processing by using the Processing Options tab. During reorientation PhotoModeler will set the model coordinate system to match the control point system.

There is one tricky situation that you might need to consider. If you are exporting a dxf file from a PhotoModeler project so it can be reimported back into the same project as control points for InverseCamera processing, you must again be sure of a consistent coordinate system. You started the project without control points (i.e. PhotoModeler is using its own arbitrary coordinate system) and so you must turn off the project scale and rotation before the DXF export. If you do not do so, the DXF will be exported in the scale and rotation defined, and when imported will be in a different coordinate system from the internal one. You can turn the scale and rotation on and off easily with the Scale and Rotation dialog; turn it off by choosing the “None” radio button in PhotoModeler 4 and by setting each component (Scale, Translation, Rotation) to ‘inactive’ in PhotoModeler 5.