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Which CRS would you recommend to georeference historical world maps like the ones in the London Geographical Institute - The Peoples Atlas - 1920, e.g.

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The map displays a lat/lon grid which I would like to use to pick control points. I managed to get some reasonable results simply using WGS84 EPSG:4326 but wonder if there isn't a better option.

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+1 good question - and cool site. –  Kirk Kuykendall Mar 30 '13 at 14:35
    
Excellent question and one I've often pondered when looking at a historical map! Lots of historical ellipsoids and projections to choose from... –  Erica Mar 30 '13 at 15:31
    
My suggestion is to georeferenced it in a system you can display it in later. If you set it to 4326 it will cause the longitudinal lines to converge won't it? –  Brad Nesom Mar 31 '13 at 0:19
    
Also most software may realize the marginalia are not valid coordinates for the system –  Brad Nesom Mar 31 '13 at 0:21
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3 Answers

I never used this software, but I think it would be very useful for your purpose: Mapanalyst http://mapanalyst.org/. the software is written in java and runs on windows, mac and linux. the author of the software Prof. Bernhard Jenny (oregon State University) is an expert in that field: http://cartography.oregonstate.edu/distortionanalysis.html, so maybe you could get in touch with him?

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The example map have some kind of Mercator projection (I believe that it is Miller cylindrical projection) with a Greenwich as a central meridian. most Other maps have the same projection or some kind of conical projection (like this one) which parameters you may try to guess. I suppose that Bessel ellipsoid was used for all of them - it was popular in Europe at that time. I believe that there is information about ellipsoid and CRSs at service pages of the atlas (maybe they are available somewhere). Having this in mind you will be able to create custom proj string.

Also this notes about georeferencig may be helpful.

As a conclusion I propose the following parameters for the map above:

'+proj=mill +lat_0=0 +lon_0=0 +R_A +ellps=bessel +units=degrees +no_defs '
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This isn't going to be obvious to everybody, and the CRS will probably be different depending on which map is being georeferenced. I think a more general solution or a methodology for determining the projection, like what Kirk is suggesting, would be more useful here. Perhaps you could explain what cues you used to come to your conclusion? –  Jay Guarneri Mar 30 '13 at 15:07
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@JayGuarneri, ok, more info added –  SS_Rebelious Mar 30 '13 at 15:57
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Great post. I really like how you straightened out the Bonne map. –  underdark Mar 30 '13 at 16:18
    
@underdark, thank you –  SS_Rebelious Mar 30 '13 at 18:25
    
@underdark, proj4 string added –  SS_Rebelious Mar 30 '13 at 19:52
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I've never used it, but perhaps Blue Marble's Projection Recovery Tool could be used once you've defined some control points.

The Projection Recovery Tool automates the process of determining the original projection information associated with mapping data when that information is lost and no longer associated with the data. Through a sort of reverse interpolation via the GeoCalc coordinate system engine, the application determines the most likely projected coordinate system used to reference vector or raster data. By comparing data to a set of known control points users can explore the parameters of the most likely candidates quickly and accurately. Projection recovery is perhaps most applicable to raster data in that it is quite common for raster data to lose its associated projection information. Use the Projection Recovery Tool to conduct an automated statistical analysis of your data to produce a quick list of the most likely candidate projections for your data. No more need for manually assigning and guessing at projections. This process will save time and money when working with data with lost projection information by automatically doing the comparison for you. The Georeferencing tool within the Geographic Transformer allows users to assign coordinates to an image through an easy to use point selection tool to locate the image in the world. Once an image has been georeferenced, it can be transformed to any other appropriate projection for display in other GIS software.

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