Okay, first off, thanks for sharing.
Second, I am having trouble wrapping my mind on how to use this (not sure if I am just having a major brain-fart or what). When I look at most (Earth) maps with this, the map is always wider then it is tall. Even most fictional maps are presented like this. How is this is a square? If you show a round globe flattened onto a rectangular piece of paper, shouldn't it be twice as wide as it is tall? (if the globe is perfectly round.)
Is it that most maps cut-off a major part of the top and bottom of this grid? (and I get that the top and bottom edges really represent a pinpoint and not a line as illustrated)
Where is my thinking going askew here?
EDIT: I think I answered my own question - most maps ARE indeed missing pieces of this. the answer was (literally) right in front of me - I have a huge world map right above my monitor on the wall. Apparently the entire bottom row and at least half of the top boxes are missing.
Thanks again - someone ask me for a 'timezone' map for the Forgotten Realms awhile back, and this will work-out perfectly. I just need to add the lines for the arctic and tropic zones now.