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Technical Issues: Old Maps

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Image Gallery 7 - Making use of old maps


Ayres

from
Cherokee Removal: What's in a Name?

There are a large number of historical maps that allow us to see the geography of the world as it was known at the time of events we study. Unfortunately, it is not simply a matter of cutting and pasting these maps to enable their use in a geographic information system. They may lack accuracy and, almost certainly, their projection does not match that of the basemap you may want to use (more often than not, web mercator). Some “rubber sheeting”, or rectifying, of the historical map with the modern basemap is required.


The single best source of digitally available historical maps is the David Rumsey Map Collection. This collection of mostly 18th and 19th century maps contains over 40,000 items which may be downloaded in formats ranging from thumbnail to high resolution. Many of the maps in the Rumsey collection are rectified and can be downloaded and used. The site also provides a convenient Georeferencer Tool. Another easy (though not the most precise) way to rectify old maps like those in the Rumsey collection is to use the transformation tools available in Google Earth as suggested in the series of slides at right. Once the map image is slid, rotated, and scaled to fit as best you can, the file can be saved and added to an online map using a service like ArcGIS Online.

 

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