Unknown Coordinate System of 1900s USGS Topographic maps

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10-20-2015 12:33 PM
D__SamuelRajasekhar
New Contributor III

Hello All,

I have 1890s & 1900s vintage scanned Topographic Maps. The Coordinate system is obviously a Geographic Coordinate system since only the lat/longs are represented in the tics. the datum is Mean Sea Level. Perhaps they are in Polyconic Projection and Clarke 1888 ellipsoid. based on the corner Tic coordinates they were geo-referenced to Datum NAD27 because of convenience.

I am not an expert in geodesy, but how much shifts are expected for such transformations? Is such practice acceptable? There seems to be no sure answer. Any guidance/help is greatly appreciated.

-Samuel

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MelitaKennedy
Esri Notable Contributor

Okay, the map's 1:125000 and there's very little detail that would work for georeferencing. I retract my earlier statement! You may have to use the corner points as the best you've got and call it NAD27. If you can identify a few other interior points, that might help--but the reference data should also be in NAD27, not NAD83 or WGS84.

Melita