.obj change coordinate system

[MINE]

Hi all,

I need to import a mesh in an obj file into PS, which is saved in a local coordinate system.

Is it possible in PS to move the mesh to match the UTM 32N coordinate system by tieing some of the vertices in the mesh to specific coordinates??

Thanks

[Alexey Pasumansky]

Hello MINE,

In principle, if you have exact coordinates in UTM of some certain model vertices, it is possible to calculate transformation matrix for coordinate conversion from local coordinates into UTM.

[MINE]

Hello Alexey,

Yes, that is true, but I don't know how to apply the transformation to the mesh, so its position matches the photos and the GCP's in PS.

[Alexey Pasumansky]

Hello MINE,

To estimate the transformation from one coordinate system to another it is necessary to know coordinates of the same point in both coordinate systems. Coordinates in local system of mesh vertices may be derived from OBJ file, but do you have the coordinate information for corresponding points in UTM?

[MINE]

Hello Alexey,

I initially created the mesh in PS working in UTM and then exported it and altered it in another program. I then saved it in obj, but it wasn't possible to save it in UTM, so it is saved in a local coordinate system instead. This means that I do know the UTM position of some of the vertices.

I now need to put it back in PS and then use the vertices with known position to place the mesh in its original position in UTM so it is still correctly positioned compared to the GCPs and the photos I used when I created the mesh originially, so I can use these to create an orthophoto.

[Alexey Pasumansky]

Hello MINE,

And why you have to switch from local to UTM? In case another application you were using is not able to work with big values (X and Y coordinates of UTM projection), you can use Shift fields in model Export/Import dialog  to subtract the same big value from all the vertices coordinates (to shift the model).