Georeferencing a raster overlay using one point, true north, and a bar scale

[LukeMazza]

I have a bunch of maps I'd like to overlay in ArcMap but almost all of them don't have more than one point I can georeference. These are cave maps and they often have one entrance which I have coordinates for, an indication of true north, and a bar scale. I assume that's enough to get me in the ballpark but I'm not really sure where to start. Any tips would be appreciated.

[NidhinKarthikeyan]

You should have a minimum of 4 Control Point to Georeference a raster. Else you should have an existing spatial data (target data), such as Georeferenced raster or a Vector Feature Class of the same location. Take a look at this weblink: http://resources.arcgis.com/en/help/main/10.2/index.html#//009t000000mn000000

[NeilAyres]

You can, carefully, mark 3 other points on your map scaled off from your single origin.
Then re-scan and use these for the GCP's to do the image GeoRef.
Very do-able.
Cheers,
Neil

[LukeMazza]

That's a great idea Neil. Thanks!