Lord Baltimore commissioned the Bohemian-Dutch merchant Augustine Hermann to produce a map of his Maryland colony in exchange for a large land grant near the head of Chesapeake Bay.  Hermann’s map was published in England in 1670.

In his A Biography of a Map in Motion: Augustine Herrman’s Chesapeake, Prof. Christian Koot uses contemporary accounts of Dutch and English navigation, land survey, and maritime map-making methods to imagine how Hermann gathered data and produced his map.

How accurate was Hermann? I used GIS software to find out. 

I laid two prominent points from the Hermann map over GPS ground truth shown in a modern basemap — Elk Neck Point near Hermann’s Bohemia Manor in the north and Cape Henry at the mouth of the Chesapeake in the south.

How accurate are the points in between?  See for yourself.  Pan and zoom, swipe the bar to compare in the map here.