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Could perhaps John Shanton or some techno-type at USGS
answer this question? A researcher here wants to know what
is the best horizontal accuracy one can expect to achieve
using a USGS 7.5' topo map. He was told by a cartographer
that the position of, say, a building would come within 6
feet of a spot on one of these topos. I understand that six
feet is about fifteen thousandths of an inch on these maps.
Well, .015 is also the size feeler gauge I use when setting
the points on my '65 Ford and would be quite a small
measurement on a topo map. Which leads me to believe that
there's a limit of accuracy one should expect from a topo
map. I would suspect that any surveyor, for example,
neededing an accuracy better than six feet should use a GPS
instrument. - PML