[Proj] Common term for geographic and projected coordinates?

Gerald I. Evenden geraldi.evenden at gmail.com
Wed Feb 4 10:22:57 EST 2009

On Wednesday 04 February 2009 5:19:12 am Mikael Rittri wrote:
> Gerald wrote:
> > A second issue arose and is the preferred or official designation of
> > lat-lon-h coordinates. Is geographic or geodetic preferred?  I have a
> > tendency to use the two designations interchangeably and mix them freely
> > in emails and documentation.
> >
> > Anyone want to nit-pick over this usage.  :-)
> Well, h is a hairy issue, with all the different kinds of height.
> But for lat-lon, both "geographic coordinates" and "geodetic coordinates"
> would be correct, as far as I understand it.
>    But "geographic coordinates" is probably more common (Google gives 585
> 000 hits for "geographic coordinates", and only 19 700 hits for "geodetic
> coordinates").
> Now to my own question: is there a general term that includes both
> geographic coordinates (lat-lon) and projected coordinates
> (easting-northing), as opposed to pixel coordinates?
>    I am trying to document a method that tranforms pixel coordinates to
> either projected or geographic coordinates, depending on whether the
> window is presented with a map projection or just as lat-lon (all right,
> Pseudo Plate Carrée).
>    As you see, I haven't found a snappy way to express it.
> I can only think of "georeferenced coordinates", but is there a better
> term?

Isn't this just a "scale" issue.  That is, you are scaling and translating the 
XY from the projected data to the units of the display device.  The only 
added hassle is that a pixel represents an area rather than a point.

To go from pixels back to the projected data and eventually to geographic data 
is merely unscaling and untranslating and then inverse projection.

Why isn't "scale-translation to and from display units" a useful phrase.  May 
not be snappy but seems clear to me and, I might add, I don't think we need 
any more snappyness.  ;-)

The whole religious complexion of the modern world is due
to the absence from Jerusalem of a lunatic asylum.
-- Havelock Ellis (1859-1939) British psychologist

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