Anybody who has experience with dealing with hPa as vertical coordinate
in GIS or related systems? Or with the WMS / other OCG standards?


We have implemented software for displaying 2D and 3D meteorological
data [1] in accordance with the WMS (Web Mapping Services) protocol [2].



However, the spesifications for WMS 1.1.1 requires that the vertical
coordinate is an EPSG code [3]. (An EPSG code is a unique shorthand code
for a geographical coordinate system or projection - example: the
EPSG:4326 is the WGS84 (World Geodesic Datum))


The hPa vertical coordinate is not deemed worthy of the honor of an EPSG
code (or we haven't found it). This is not really surprisingly: Using a
layer whose height is highly variable as vertical coordinate is probably
quite absurd for most geographers and GIS people.



To me, it seems we have three strategies:

= Ignore the problem. This leaves us with an WMS server that is "not
really WMS".

= Find an EPSG code for hPa vertical coordinate. This probably involves
hunting down a member of some EPSG working committee and use thumb
screews untill the EPSG standard has been revised to suit our needs.

= Circumvent the problem by using another "dimension" than "elevation".
(See [3]). The problem is that not all clients may recognise what we
mean by our server-defined dimension "hPa-elevation" (or whatever we may
care to call it).



Does anyone have any experience of how to deal with this?



References:
[1] Web client for or meteorological WMS server: http://metoc.met.no

[2] WMS is an OCG (Open Geospatial Consortium) standard
http://www.opengeospatial.org/


[3] From the OCG WMS 1.1.1 spesification:

All Dimensions in a Capabilities XML response are server-defined, with
two exceptions. The dimensions named time and elevation are privileged
special cases, predefined as follows:
Dimension name="time" units="ISO8601" /
Dimension name="elevation" units="EPSG:vertical_datum" /
The units "ISO8601" refers to the Time representation specified in Annex
B. The units "EPSG:vertical_datum" refers to elevation units and a
reference used by one of the European Petroleum Survey Group [ref. 13]
vertical datums (use the actual datum number in place of the string
"vertical_datum").
EXAMPLE: Elevation units given as "EPSG:5030" means "meters above the
WGS84 ellipsoid."


Regards, Jan
--
Jan Kristian Jensen
Norwegian Defense Research Institute

Remove the obvious from the email adress to email me.