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Your analogy is not quite appropriate. An upside down mug is "wrong". The mug looses its meaning and you have to turn it around to use it as a mug. That's not the case with a map. An "upside down" map is just as valid as a right side up map. The fact that it is upside down is not supposed to mind blowing, it's the fact that it isn't upside down at all. We are just used to it being represented this way up, but there's…
> An "upside down" map is just as valid as a right side up map. Is it as useful and/or efficient though? I could write a phrase in English from right to left and if you really wanted you could read it, but it would be highly inefficient. An efficient society sometimes has to pick conventions (how to write text, how to print a map, what characters to use, etc) and I find not interesting to point that other conventions…
Also thinking of maps and Japan: where I am from (Germany) public overview maps of parks or street maps usually have north as up. In Japan however it is very common for those maps to have up as the cardinal direction you are looking at the map at. So if you are looking at the map in a western direction, the map will have west up. So for walking the map is straight up, backwards down, left left and right right.
Like that it is very easy to know which way to go. Want to go to some place that is on the left on the map? Turn left!