David Rumsey Map Collection & 'Georeferencer'

Might be of interest to some.
Massive collection of online maps, all periods.
Georeferencer thing looks good for creating overlays etc., though I cannot pretend to understand it yet.

David Rumsey Historical Map Collection | The Collection

 

Just playing with the overlay creator.
Looks rather good.
Only a few reference points and it starts to look quite handy. Adjust opacity & view with swipe, magnifier etc.
Testoverlay - Compare maps

People have definitely asked if there was such an easy to use tool in the past.
Certainly seems much more straightforward than the last time I tried to do one on Google Maps.

 

Adding many more reference points would doubtless improve, but using a grabbed sketch plan of Arnhem and overlaying starts to show the easy power of the thing.
Arnhem_Map_2.jpg