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A map dealer asks what does the "T" or "AT" stand for on
elevations written in long-hand on 7.5' USGS provisional
topo maps. I promised him I'd ask the list.
Speaking of this series, has the USGS updated the
explanation sheet describing topo map features recently?
A single-sheet giveaway describing all the mundane map
features and additionally some of the more technical aspects
such as definitions of what all the tick marks along the
edges mean would be very helpful for the common map user.