WCS and Reprojection with TileItem

Thu Feb 1 06:11:01 PST 2007

Hi Norman,

I tried to do a request on his website, but i still have the same problem that i
 already have on my own server.

when i ask a simple resquest on the srtm (thanks for the link), i can see the
data on epsg:4326
http://iceds.ge.ucl.ac.uk/cgi-bin/icedswcs?VERSION=1.0.0&SERVICE=WCS&REQUEST=GetCoverage&coverage=srtm&width=400&height=400&bbox=2,49,3,50&crs=epsg:4326&FORMAT=geotiff_int16
this links works fine, but they are no reprojection.

Now when i try to convert to the UTM zone on this data (France, north to Paris,
so UTM zone 31N : epsg:32631), i have only this :
http://iceds.ge.ucl.ac.uk/cgi-bin/icedswcs?VERSION=1.0.0&SERVICE=WCS&REQUEST=GetCoverage&coverage=srtm&width=400&height=400&bbox=425000,5427000,500000,5539000&crs=epsg:32631&FORMAT=geotiff_int16
this links give me the good boundingbox but not the data inside ! only Om data
elevation !

Now if i add on this request : RESPONSE_CRS=epsg:32631, i have the same result,
http://iceds.ge.ucl.ac.uk/cgi-bin/icedswcs?VERSION=1.0.0&SERVICE=WCS&REQUEST=GetCoverage&coverage=srtm&width=400&height=400&bbox=425000,5427000,500000,5539000&crs=epsg:32631&FORMAT=geotiff_int16&RESPONSE_CRS=epsg:32631

Now if i try the response_crs in 32631 and the crs in 4326 with bbox in 32631, i
have always this same 0m elevation data :
http://iceds.ge.ucl.ac.uk/cgi-bin/icedswcs?VERSION=1.0.0&SERVICE=WCS&REQUEST=GetCoverage&coverage=srtm&width=400&height=400&bbox=425000,5427000,500000,5539000&crs=epsg:4326&FORMAT=geotiff_int16&RESPONSE_CRS=epsg:32631

So i really don't understand where is the problem.

Thanks for this site.

I will see now the zip we can find on the site to see the mapfile i used to do
this excellent and nice site.

But i'm still convinced mapserv has a bug because theses kinds of requests are
possible in WMS Service !

Cordialy,

Jérôme

Selon Norman Barker <nbarker at ittvis.com>:

> Hi Jerome,
>
>
>
> I know Jeremy Morley doesn't watch these lists too much, but his ICEDS
> service
>
>
>
>
http://iceds.ge.ucl.ac.uk/cgi-bin/icedswcs?SERVICE=WCS&REQUEST=DescribeCoverage&Coverage=srtm
>
>
>
> offers srtm data in different projections.
>
>
>
> His website also gives full config details for MapServer configuration, a
> subset of which is on the MapServer website under WCS use cases.
>
>
>
> Thanks,
>
>
>
> Norman
>
>
>
> ________________________________
>
> From: UMN MapServer Users List [mailto:MAPSERVER-USERS at LISTS.UMN.EDU] On
> Behalf Of Jérôme Martin
> Sent: 01 February 2007 01:06
> To: MAPSERVER-USERS at LISTS.UMN.EDU
> Subject: [UMN_MAPSERVER-USERS] WCS and Reprojection with TileItem
>
>
>
> Hi,
>
> I'm using mapserv like WMS and now, I would like use the WCS service to get
> DEM, from DTED files.
>
> To do this, i used gdaltindex software to create a shapefile to have only one
> entry on my mapfile with the "TILEITEM" keyword.
>
> I precise my dted file are LatLon, in EPSG:4326.
>
> So when i did a request Getmap from the server, i had the result i wanted
> for, in lat-lon.
> But my problem was when i tried to send the request, but with CRS=epsg:32631
> (UTM Zone N31) by example (BBOX in 32631 too), nothing work and the server
> send me a file with the good boundingbox envelloppe, but with no data, only
> 0.
>
> When I tried to do a resquest with CRS=epsg:4326 (BBOX in 4326)  and
> RESPONSE_CRS=epsg:32631, i have the same empty 0 file, and the server doesn't
> warn me any error. Just a file with 0m data elevation.
>
> I'm really surprised, because the OGC documents about the WCS Service tell
> the response_crs can be used to have a reprojection, and the how-to user case
> from the mapserver website tell this option can be used.
>
> So when i try to put only one file with the DATA keyword, i was really
> surprised to see a request in another crs gave me the good reprojection and
> the right results, so the reprojection works on only one file, but not in
> shapefile tileitem. So Did I do something wrong, or this is it a bug from
> mapserv ?
>
> Moreover, i am already using mapserver with the WMS service, and i have only
> shapefile tileitem entries on my wms mapfile : the reprojection works
> perfectly ! (the shapefile are created from the gdaltindex tool).
>
> I can't put each file on my mapfile, because i thousands files and this will
> be affect the performances of mapserv (moreover, i think it exist a
> limitation of the maximum number of layers in a mapfile).
>
> So do you would have any idea about this problem, or do you know an easy
> exemple of a wcs service server who delivers DEM data in differents
> reprojections ?
>
> thanks you for the help,
>
> sincerly,
>
> Jérôme Martin
>
>
>
>
> J'ai donc configuré un server wcs, et j'ai également crée un fichier shp via
> gdaltindex afin de n'avoir qu'une seule entrée dans le mapfile regroupant
> plusieurs fichiers DTED.
>
> Je précise que les fichiers sont en latlon EPSG:4326
>
> En faisant une requête avec CRS=epsg:4326, j'ai donc le résultat attendu,
> soit un fichier tiff (ce que je voulais) en latlon.
> Par contre, lorsque je fais une requête avec CRS=epsg:32631 (UTM zone N31)
> par exemple, là, tout se complique puisque la réponse que me renvoye le
> server semble bonne au niveau des dimensions, mais je n'ai uniquement que des
> 0, les données d'élévation disparaissent.
>
> Je précise que j'ai déjà un server WMS utilisant exclusivement des tileindex
> (via gdaltindex) et que la reprojection se passe parfaitement. Mais en WCS,
> rien ne marche plus pour la reprojection.
>
> Par contre, si je prend un fichier seul (fichier.dt1) que je rajoute dans mon
> mapfile wcs, alors dans ce cas là, la reprojection marche bien et ne pose pas
> de problème. Je ne peux cependant pas résoudre mon problème comme cela car je
> ne peux inclure des milliers de fichiers dans mon mapfile, et je ne peux pas
> non plus modifier les fichiers dted en entrée (d'autant plus que je ne veux
> pas distinguer séparement chaque fichier dted dnas mes requêtes).
>
> Comment puis-je résoudre mon problème ? quelqu'un a-t-il déjà été confronté à
> ce type de problème sous WCS ?
>
> cordialement,
>
> Jérôme   <http://www.forumsig.org/editpost.php?do=editpost&p=93083>
>
>