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I am trying to georeference a map that has meridians and parallels etc. but no projected grid displayed. I can get the coordinates of the meridians/parallels fine, so georeferencing should not be an issue. HOWEVER the only projection information is "Universal Transverse Mercator" and no zone information is given. The map in question spans western Canada so zones 10N-15N.
It is probably projected in zone 11 or 12 but how to be sure for georeferencing?
The central meridian of the UTM systems is at 93°W +/- 6° and has a value of 500000m in the local system.
So you have to look up those central meridians and see which aligns with your UTM grid. The next central meridian will be about 300 km away, and appear bended in the chosen UTM projection.
You could assign a projection to your map in the platform you are working in. For example, you could first try to assign a UTM Zone 11 North projection and overlay the map with a base map (e.g. Google Layer) and see whether the features of your map align with the features of the base layer. If not, assign UTM Zone 12, and so on.
