OK, a bit of technical information on charts here, just in case anyone is interested.:
A chart will always show the latitude and longitude since that is how navigation is done. It is crucially important that the latitude scale running down both sides is used and never the longitude scale across the top and bottom. The lines of longitude (NS) converge at the poles and so will never be 60 nm apart except at the equator. Most charts will not show nautical miles, you just read from the longitude scale. Furthermore, the scales are in degrees, minutes and decimals of a minute. Positions are given in this way too. One minute is a nautical mile, 1/10 of a minute is a cable's length and 1/1000 of a minute is a fathom (6' or 2m). For instance one of the navigation buoys in the mouth of the Medway is at 51°25'.813N, 000°43'.945E. Note also that the latitude is always given as two figures (ie 00 to 90) whereas the longitude is given as three figures (ie 000-180).
See any book on navigation at Day Skipper level or above.
I've enclosed a tiny part of one chart showing Walton Creek, Essex. Notice on the right hand side 51°52'N and 51'.5. The second, lower value is minutes only and the "ticks" are tenths of a minute, near enough 600'. Notice also the ticks across the bottom are much closer than down the sides. The figures in the water are depths in metres and tenths (in smaller type). Underlined values are drying heights.