On map scale and raster resolution
I am sure if you have used any imagery data to make maps then you have at one time or another asked yourself, "What resolution should the image be for me to be able to detect features in it?" Well, you don't need to guess, because there is a mathematical relationship between the map scale and the image resolution.
In 1987, Waldo Tobler, renowned analytical cartographer (now emeritus from University of California-Santa Barbara) wrote, "The rule is: divide the denominator of the map scale by 1,000 to get the detectable size in meters. The resolution is one half of this amount." Tobler goes on to note, "Of course the cartographer fudges. He makes things which are too small to detect much larger on the map because of their importance. But this cannot be done for everything so that most features less than resolution size get left off the map. This is why the spatial resolution is so critical."...(read more)
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