My team at the Stanford Geospatial Center is working on a geo referencing project of historic maps of Africa, all from the 1700s (I believe). We are in the process of setting up the best workflow for referencing the continental maps but are having some difficulty in identifying the most suitable projection in ArcGIS to use as the base to reference to.
Most of the maps include a graticule which helps narrow down the projection type to some kind of Equatorial projection. We've played with a few stock projections types in ArcGIS and came up with the following images based on the Van Der Grinten projection.
The graticule looked like a match between the base and the image but as you can see it wasn't.
What I'm hoping is someone here with more projection experience than I will be able to spot the correct type of projection to use as the base from the graticule and the uniform deformation in the rectified image.