First of all, Thank-you for providing such great software! You're help on the forums is also much, much appreciated!
My question arose while trying to calibrate an image for a new raster map.
I can't figure out which are the correct settings for projection and datum for United States Geological Survey Topographic maps. The maps I'm using are the historic maps, originally published in the 1950's.
The original maps state they are drawn using: 1927 North American Datum Polyconic projection
The XML metadata file further states the geodetic data used was: NAD27 And the Projection used was: Polyconic
For your reference, a crop of the map with the datum notes is attached to this post.
Can you help me?
I wish to calibrate the map via the 1927 dataum, as that is what the outline and boundaries of the image were drawn to.
Polyconic isn't supported by OkMap, try to use "Transverse Mercator" or "Longitude/Latitude" projection. For datum choose one of "North American 1927 ...." datum depending on the zone of the map. You should use "<Customized projection>" and set all parameters manually. If the map covers a little zone, errors should be minimal.