projection

[ROMAN ANTONI KAMINSKI]

*<>*>>From g.help
The definition are from g.help
The authors are James Westervelt, Deb Brinegar and Mary Martin
I don't discuss about if the definition are good or poor
*<>*>A map coordinate system is either a geographic system
*<>*>(like UTH or latitude/longitude) or an arbitraly coordinate system
*<>*>used to reference the locations of objects in a two-dimensional
*<>*>space. 
*<>*
*<>*The geographic system refers to the location on the Earth, not on the
*<>*map.  Geographic coordinates can often be determined from a map if
*<>*the graticule is plotted.  But referring to geographic coordinates
*<>*as a map coordinate is misleading.
*<>*
*<>*BTW, what is UTH?  
Here my error. Should be UTM - Universal Transverse Mercator 
*<>*
*<>*>A map projection describes the manner in which the spherical
*<>*>surface of the earth is represented on a two-dimensional surface.
*<>*
*<>*What about the ellipsoid?
*<>*
*<>*>It attempts to minimize distortionin area,shape,distance and
*<>*>direction.
*<>*
*<>*No map projection does all of the above.  Select one of the criteria
*<>*and a projection may used that does minimize that feature at the
*<>*expense of the others.
*<>*
*<>*>See also the reference
*<>*>"Map Projections - A Working Manual " ,Snyder, 1989
*<>*>
*<>*>And my private view.
*<>*>Projections are used eg for UTH .
*<>*
*<>*Again, what is UTH?
*<>*
*<>*>               For small area are not needed.
*<>*
*<>*Not true.
And I was sure that for e.g. area 100*100 m I don't must
to think about any projection. My plane map will be so and so
enough exact. So for small angles sin(alpha)=alpha.
Everybody can see it in books, in tables

*<>*
*<>*>I'm a civil engineer and about map projections I learned
*<>*>50 years ago.
*<>*
*<>*Very little has changed in 50 years.  Only item of significance
*<>*it the ease of computing a projection.
But I'd changed very much and forgot all what I'd learned at school

>Now I get the projection from the sample problem.
*<>*>Later the user from Geography Department will know what
*<>*>projection to use.
*<>*>
*<>*>                            BRGRDS Romek
*<>*
*<>*Gerald (Jerry) I. Evenden   Internet: gie at charon.er.usgs.gov
*<>*voice: (508)563-6766          Postal: P.O. Box 1027
*<>*  fax: (508)457-2310                  N.Falmouth, MA 02556-1027
*<>*
                            BRGRDS Romek