[Geotiff] Vertical Coordinate Systems and Datums - tag best practice

[Max Martinez]

Frank,

For horizontal coordinate systems, there was some confusion with people
providing "unit overrides", i.e., specifying a unit that did not match
the unit implied by the coordinate system. We consider this a bad
practice (but of course have to accommodate it with configurable
behavior in our software). The same thing can happen with the
VerticalCS. What are you suggesting here? Is the practice to always
provide the units but make sure they match what is in the CS definition?

Also, if you don't specify a vertical cs for ellipsoidal height, there
isn't really a reliable automatic way for software to identify dems.
Perhaps not a big deal because a lot of current data doesn't have the
vertical information available anyway, but it would be nice. Other
approaches would seem to be awkward though (e.g., repeating the
horizontal datum and using the 3d ellipsoidal epsg cs code).

Max

-----Original Message-----
From: geotiff-bounces at lists.maptools.org
[mailto:geotiff-bounces at lists.maptools.org] On Behalf Of Frank Warmerdam
Sent: Monday, February 07, 2011 2:01 PM
To: liblas-devel at lists.osgeo.org; GeoTIFF
Subject: [Geotiff] Vertical Coordinate Systems and Datums - tag best
practice

Folks,

I have tried to capture some suggested "best practice" on GeoTIFF tags
for vertical coordinate systems in the GeoTIFF Trac wiki at:

   http://trac.osgeo.org/geotiff/wiki/VerticalCS

Let me know if folks think this is wrong or if you have improvements you
would like to make.  The advice here should apply in the GeoTIFF context
as well as in .las files, jpeg2000 and other contexts based directly on
GeoTIFF tags.

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

_______________________________________________
Geotiff mailing list
Geotiff at lists.maptools.org
http://lists.maptools.org/mailman/listinfo/geotiff