A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Sean C
Date: 2021 Dec 11, 15:08 -0800
"Is there a world map showing deviation from vertical...?"
I thought for sure I had seen a nice one somewhere, but I can't find it now. However, I did find this Google Earth plugin (attached) which will show the DoV - but unfortunately only for U.S. territory. (Screenshot of coverage also attached.)
The same site offers another plugin called Rings (among others), which I have mentioned before.* The plugins are a little tricky to use: you need to refresh Google Earth each time you move to a new location, either by selecting "Refresh" from the "Edit" menu or by pressing [Ctrl] + [R].
In the case of the DoV, it appears they are using a NOAA site which hosts some NGS tools for the calculations.
* NB: the link in my old post no longer works.