Lining up geo-referenced imaged

Celeste

I have two large (2' x 3') pieces of a map that I have scanned, and I now am trying to geo-ref in GlobalMapper. In order to get the edges to line up, is it better to have less or fewer points? Or is there a way to "nudge" an image to get the edges to line up exactly? I think the image was skewed ever so slightly during the scanning process. I have UTM grid lines and have tried using the same points on each map, but I still don't get a great fit.

global_mapper

In general the more the better, but really if you did maybe 9 points (i.e. each corner and then midpoints along each edge, then a point in the middle, assuming you have known coordinates or corresponding points for each), that would be more than enough for most cases, so long as you choose a rectification projection that is not shaped significantly different from the original map projection.

Let me know if I can be of further assistance.

Thanks,

Mike
Global Mapper Guru
gmsupport@bluemarblegeo.com
http://www.globalmapper.com