Georectifying a historical map

Yesterday I had the opportunity of working with a map from the David Rumsey Georeferencer page. I was given an old map of the globe (shown bellow), and I had to match the places with a current map of the world. That is, telling the computer where arbitrary places I chose (like Bogota) are in the ancient and in the current map.

Ancient map from David Rumsey Georeferencer page

As I worked on this, the computer kept getting better at “guessing” where the point would be on the other map given the scale that it was creating based on the previously placed points. This was my first time working on this, but I think I did a good job. You can see the final product here, and you can see interactive version of the map where it is “over” the current map and you may change opacity of the map to see how precise the work is.

The interactive version of the map made me realize that no matter how precise I tried to be, I could never make the two maps align perfectly. Particularly because of the way the ancient map is painted. In the animation you may observe that the shape of America is curved to the right with respect to the actual map. it seems like the maker of the ancient map intended to show the roundness of the globe in the map. This would be a clear problem if we wanted to find a place in the ancient map using longitude an latitude that correspond to the current map. However, it is interesting to see older maps as we can observe how the world was perceived and maybe understand why certain decision were taken in different times of history where this map was used.


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