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To answer your question Eric. The geodetic co-ordinates seem have been selected arbitrarily for the example you have given. It is the same for Adelaide, Clayton bay or anywhere in Australia. For Tehran you would need to first find out what is considered to be the local centre of any city or township and then get the co-ordinates from there. If you move the box with your cursor it will update the co-ordinates for you.
The current system is pretty accurate and down to 200mm I think. Survey marks will be accurate to 1mm or so generally as those are used for horizontal and vertical control in a given datum. However, for GPS 200mm is within the standard deviation as I understand it. Its been about 27 years since I thought about this stuff (ex cartographic technician and surveyor in the Australian Army), so I might be a bit rusty.
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