NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Gary LaPook
Date: 2016 Dec 30, 21:29 -0800
This is relatively straight-forward, though perhaps not "easy". Google Maps does not ordinarily include a lat/lon grid. It's available in the API (the programmable version of Google Maps), and here's a demo that will do just that: http://www.bdcc.co.uk/Gmaps/ll_grat_v3_demo.htm. You'll have to play around with it a bit to get what you want, but I'm including an image, below, of a detailed example that I hope is fairly close to what you requested. Maybe good enough?
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But Mercator small scale plotting sheets have been in use many, many years before navigators had access to electronic calculators so graphical methods and Merdional Parts were used for making Mercator plotting sheets and Mercator charts.
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