I have a somewhat odd situtaion. A client has provided me with a Shapefile that has no projection information, along with an image of the map that it corresponds to. I have run some coordinates through WhatTheProj and it matches no known EPSG code.

So, my next thought is to somehow create a projection that maps coordinates correctly. I know how to create a Proj4 string and test whether it's right, but I don't actually know anything about projections or how to go about this. Are there any tools that would help?

marked as duplicate by PolyGeo Dec 2 '18 at 23:27

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    It sounds like a 'local' datum, common on mining sites (it keeps the easting and northing numbers small, easier to read). Do you know which projection it is? i.e. Lamberts, Transverse Mercator, Albers etc.. you can usually create one by taking an existing projection and modifying the false easting and northing if that was how they arrived at their 'local' datum but sometimes they're based on an uncommon projection - which you will need more information for. If you have from coords and to coords that are accurate you can create a transformation file to use with spatial adjustment toolbar. – Michael Stimson Dec 2 '18 at 23:18
  • Thanks. It's an urban area. The file was created from Adobe Illustrator apparently, by people with no GIS knowledge. I don't have access to Esri, are there any free equivalents? – Steve Bennett Dec 2 '18 at 23:24
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    Have a read of gis.stackexchange.com/questions/33208/… about transforming a shapefile using control points; note that this is only an Affine transformation (scale and rotate) so if your to locations are in a different projection there will be some distortion. – Michael Stimson Dec 2 '18 at 23:42
  • @polygeo Thanks. I think Michael's link is more useful, because it focuses on custom projections, not finding a standard one (which I established doesn't exist). – Steve Bennett Dec 2 '18 at 23:48
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    Try searching the city name + "coordinate system" or "map projection" sometimes you can find information that way. – mkennedy Dec 3 '18 at 18:02