Clarify map datum

[colinsauze]

I don't see the map datum specified anywhere in the rules. I'd assume its WGS84, but that should really be specified somewhere.

[tsaoyu]

rules/main.tex

Line 138 in 98ae36a

decimals, e.g. 60.3456º (chart datum: WGS-84).

mentioned the data datum. However, the map datum is missing.