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Georeferencing Map with Paris Meridian

Question asked by josh_silic on Oct 22, 2016
Latest reply on Oct 24, 2016 by GSCUser85

Hello everyone,

First off, please excuse my ignorance on this topic. I am working on a project for a professor that involves georeferencing a historical map of Africa. It seemed easy enough until I realized my map was consistently 2.33 degrees off. Upon looking through the projections in ArcMap, I noticed that there was a projection called Voirol 1879 Paris. I also noticed that there are projections that use degrees and ones that use grads. I'm pretty sure that the map uses the Paris meridian, but I am unsure of how to tell if it is in grads or degrees. So I have three questions:

1. Is there a way to tell if the map is in grads or degrees?

2. Would I be able to reference it using the Voirol 1879 Paris projection and then transform it to a projection that uses the Greenwich meridian?

3. If it is possible, what would be the best way of accomplishing this?


I have attached the map in question. Any help would be greatly appreciated!