So in lieu of orthorectification (the drone I'm using does not provide geographic data) I have decided to try georeferencing as a means of overlaying aerial photography onto my DEM. Before I go out there and start taking some control points with the differential GPS I was hoping I could get some advice. I've done this in class before and if I remember correctly 6-10 control points is optimal per image, correct? Secondly, I am doing this for an archaeological site on a mountain the Andes. So I can survey the actual units for control points, but other than that, there's not much else I can use as control points in some areas of the mountain. There's cacti here and there, but nothing that really stands out. In a classroom environment I've done this with urban maps where buildings and road intersections could be used. This is the desert and pretty barren. Also, if someone could explain the process of georeferencing to me a little better I'd appreciate it. I understand labeling control points and what not and giving the image a projection to match the DEM. But the end result should be a mosaic of the images I've gathered, correct? Thanks again for your help!