Wednesday, March 16, 2016

The Cassini Topographic Maps

The first large-scale topographic maps based on geodetic measurements were done by the Cassini family in France. The map set (182 sheets) took over fifty years to complete and was worked on by four generations of the family between 1750 and 1815. Prints of these maps are held by the Maps Division of the New York Public Library. They very nicely let me take some out of hibernation for a look. 
Here is the cartouche describing the triangulated geodetic network in French. The scale is in toises-a measuring apparatus of the time, it works out to 1:86,400
Here is an image from the index map
The road network is so accurate that it can be overlaid on top of modern aerial photos. Here is another example from the northern tip of France. 
Seeing these maps in person in pretty amazing! I could stay all day photographing these but at some point I will need to move on  Here is one final picture 
Here is a link where you can browse the entire map set.