[Proj] Re: Distance measured in Mercator projection
Christopher Barker
Chris.Barker at noaa.gov
Wed Jul 9 17:53:15 EDT 2008
strebe at aol.com wrote:
> Not so. The Mercator is conformal. The scale factor is the same in all
> directions at any particular point.
yes, but it does change with latitude, so if you are measuring between
two points that are very different (by some definition of very) in
latitude, then the scale varies over that distance. If you use the
latitude of the center of the line, you'll get pretty close, though.
If you're measuring really long distances, you're better off using
spherical (or ellipsoidal) geometry.
Also note that a straight line on a Mercator projection is not a great
circle so, for long distances, you need to be clear about what you mean
by distance!
And as a note, the Mercator projection is pretty handy for 21st century
navigators, too!
-Chris
--
Christopher Barker, Ph.D.
Oceanographer
Emergency Response Division
NOAA/NOS/OR&R (206) 526-6959 voice
7600 Sand Point Way NE (206) 526-6329 fax
Seattle, WA 98115 (206) 526-6317 main reception
Chris.Barker at noaa.gov
More information about the Proj
mailing list