USGS DEM and OGC WMS -- Bug
nbarker at RSINC.COM
Wed Jul 27 09:59:12 EDT 2005
From: Julien, Heryk [mailto:hjulien at nrcan.gc.ca]
Sent: Wednesday, July 27, 2005 2:40 PM
To: MAPSERVER-USERS at LISTS.UMN.EDU
Subject: RE: [UMN_MAPSERVER-USERS] USGS DEM and OGC WMS -- Bug
This is the first time I get a request to add a USGS DEM to Mapserver.
I would like to use the original USGS format to be able to query the DEM using the WMS getFeatureInfo.
If I convert the USGSDEM to a simple raster (ex:*.tiff) don't I loose the elevation data?
WCS is interesting but I can't use WCS for now since our web clients are not compatible with this format.
I will reply to the whole group, since there is a bit of a UK mission to encourage WCS!!
It is possible (indeed I would encourage it) to create a WCS, and then to make WMS calls to retrieve a display format
of this data, so;
http://host/my.map?REQUEST=GetCapabilities <http://host/my.map?REQUEST=GetCapabilities&Service=WMS> &Service=WMS .... or
http://host/my.map?REQUEST=GetCapabilities <http://host/my.map?REQUEST=GetCapabilities&Service=WCS> &Service=WCS
so the WMS can give you the map, and the WCS can give you the actual data, it is possible to do this with the same map file!
This means that your current web clients can use the WMS, but you are also allowing access to actual coverages.
Converting USGSDEM to 16 bit geotiff works well, and I have done this using gdal_translate.
To quote the spec;
Unlike WMS (OGC document 01-068r3), which filters and portrays spatial data to return static maps (rendered as pictures by the server), the Web Coverage Service provides available data together with their detailed descriptions; allows complex queries against these data; and returns data with its original semantics (instead of pictures) which can be interpreted, extrapolated, etc. -- and not just portrayed.
I am about half way through writing a how to for this, capturing all the help I received from Steve Lime and Frank W when I approached this. Let me know if I
can help further.
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