Those things, while important to consider if you are trying to do something like hit hit a target within a few kilometers with an ICBM (http://en.wikipedia.org/

Those things, while important to consider if you are trying to do something like hit hit a target within a few kilometers with an ICBM (http://en.wikipedia.org/wiki/International_Geophysical_Year http://en.wikipedia.org/wiki/International_Geophysical_Year), are not significant when dealing with general purpose mapping.