Frank Warmerdam warmerdam at pobox.com
Mon Oct 20 09:17:28 EDT 2003

Omry Yadan wrote:
> What is the connection between URM and TMERC?
> What is the difference?
> ----------------------------------------


Transverse Mercator (TMERC) is a projection method with several parameters
- ellipsoid, false easting, false northing, central meridian, latitude of
origin and scale factor.  UTM is a "zoned" coordinate system built on
transverse mercator.  Basically by indicating a zone number (1-60) you
can lookup the central meridian in a table (or by formula).  The scale
factor is always fixed at 0.9996.  The false easting is always 500000 meters
and the false northing is either 0m (northern hemisphere) or 10000000m
(southern hemisphere).

In short, UTM is a specific set of coordinate systems built on the more
general transverse mercator projection.

Best regards,

I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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