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Date: Tue, 13 Feb 2001 18:26:56 -0500 (EST)
From: Ken Grabach <[log in to unmask]>
Subject: Re: MAP QUESTION!
Sender: Ken Grabach <[log in to unmask]>



Johnnie Sutherland's reply is very interesting, as have been many of the
other replies to this query.  Johnnie mentions the easy confusion between
a map's own grid (ooften letters and numbers, and the geographical
standard of longitude and latitude (or latitude and longitude!).  I can't
help wondering whether some confusion doesn't arise as well from a very
natural confusion over what longitude and latitude are.

Longitude lines run in great circle arcs from north to south, but they
measure direction east or west of the meridian zero (the Greenwich
meridian).   Latitude lines run in parallels from east to west, but they
measure distance north or south from zero latitude (the equator).

In other words, the lines we see running vertically on the map demonstrate
horizontal direction.  Similarly, the lines we see as horizontals on a map
measure vertical direction.

Another point of confusion may arise in the conventions used to describe
things other than x-y coordinates in mathematics or in geographic
description.  It arises all the time for me as a map cataloguer.  When I
give the coordinates I have to gove westernmost longitude first,
easternmost longitude second, then northern most latitude, then southern
most latitude.  That fits the convention of long-lat.  But when I give the
dimensions, I give the vertical dimension (top-to-bottom), then the
horizontal (left-to-right).  This is familiar to other cataloguers, who
give book dimensions either vertically alone, or vertically then
horizontally (if the dimensions are unusual or oversized).  I can think of
other conventions that can cause confusion.  In philatelic description,
top-bottom perforations are given first, then left-right perforations of
stamps are given.

I think I have confused myself enough!

___________________________
Ken Grabach                           <[log in to unmask]>
Maps Librarian                         Phone: 513-529-1726
Miami University Libraries
Oxford, Ohio  45056  USA
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