Need help aligning a DEM with georeferenced imagery & GCPs

[JohnChesley]

Hello,

I'm working on a project where I've taken point cloud data obtained from a terrestrial laser scanner and converted it to a DEM using Lastools. I've also got aerial imagery taken from a helikite that has been georeferenced with ground control points. I now need to overlay those images onto the DEM so I can create a semi-realistic terrain model.

My problem is that the DEM and the georeferenced images don't line up even though they all have the same coordinate system.  I know I could georeference the DEM to the ground control points to fix it, but the DEM doesn't have any features that I could actually match to the control points.

Does anyone have any advice that would help me get around this issue?

Thanks,
John

[JohnChesley]

Thanks a lot for you input. It's greatly appreciated!

Cheers,
John

[GabrielUpchurch1]

Glad we could help.  Good luck!

[SepheFox]

John, define projection is not used to change a projection, but to define the original projection, and this may be your problem. As Gabriel mentioned, the DEM extent shows that it originally had a geographic projection (lat/longs), but may have mistakenly been defined as UTM, so it's taking the lat long coordinates and trying to fit them to a UTM grid. Try defining the projection of this layer as geographic. You can try WGS 84 for the datum, and if this works, great. If it almost works, but is now different by ~100 feet or so, then try a different datum.

For future reference, in order to change a projection from the original, you use the PROJECT or PROJECT RASTER tool. This will actually change the coordinates into the new coordinate system.