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True lat and long in ArcMap

April 13 2011 | 0 comments
Categories: Map Data

Greetings all. I have a historic map that was drawn from a plane table surrey in 1910. It was plotted in true lat and long, with the the NW corner being one minute of longitude longer than the SW corner. This created a square map on paper, but when I georeference it based on the coordinate grid in the neatline, no matter what projection, geographic coord system, custom central meridian I try, the map displays as a trapezoid. Is there a straight lat and long system in ArcMap where the degree of longitude decreases as latitude increases, just like it is on the sphere?

This has really been racking my brain!

Thanks for the help, Kevin

Mapping Center Answer:

Esri software doesn't have an adjusted lat/lon based system that will sort of model the meridian convergence. You have to use a map projection for that. You could try equidistant cylindrical and set the central meridian and standard parallel to the center of the map. What you'll want to do is calculate the map corners (and center, possibly) in that coordinate system, and georeference or spatially adjust to it.

 http://forums.arcgis.com/threads/27915-True-Lat-and-Long-in-ArcMap?highlight=plane+table

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