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I am in the process of implementing map projection software in an
application under development and have come across an issue that
doesn't affect physical maps.  Many of the map projections which exist
greatly reduce scale distortion when plotting map coordinates to
physical media.  Everyone knows that the Mercator projection wildly
distorts the vertical axis - but by design.  On the other hand, the
oblique-stereographic projection has distortion as a function of
deviation from the Standard Circle, Line of True Scale.  The Standard
Circle, which has a center point, which also happens to be the center
point of the O-S map projection poses a dilemma for computer maps.
What is the center of the map?
 
As I said above, a physical map is fixed.  But with software, all
confusion is possible :).  I can zoom and pan.  Is the center of my map
the visible center of my display?  Or, do I tie it to the center of
the original map?  It's a rather minor distinction, but I'm curious as
to how the professional map people's perspective.
 
regards,
 
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Charles Gilley            |   All comments are my own...
Senior Software Engineer -|-
AEL/Cross Systems         |   Cross Systems - We make your radar
404-475-3633              |   see double, triple, or more.
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