I'm currently trying to orthorectify some images onto a DEM. I understand the process well enough, but the problem I've run into is that in the "image analysis" window the "orthorectify" button is not active. Apparently this means that the raster dataset does not have RPCs.I really don't have a clue what that means. I'm not very experienced in this sort of thing. If it helps at all, the images I'm trying to orthorectify are in .jpg format and I took them using a DJI Phantom 2 drone at about 65m elevation. Any help would greatly appreciated. Thanks a lot!