[Geoserver-users] GeoServer should allow WMS to use dimension without units

Rayman · April 13, 2019, 1:04pm

Hi
I am using GeoServer to add a external WMS server, but it failed because
GeoServer throw below error

13 Apr 18:37:49 ERROR [data.ows] - Failed to execute request
https://nomads.ncdc.noaa.gov/thredds/wms/gfs-004-anl/201809/20180916/gfsanl_4_20180916_0000_000.grb2?REQUEST=GetCapabilities&VERSION=1.3.0&SERVICE=WMS
13 Apr 18:38:24 ERROR [geotools.xml] - Dimension element contains no 'units'
attribute

The capabilities xml in above URL contains below dimension

It has a empty units, but according to the Web Map Service Implementation
Specification Section
C.2(http://portal.opengeospatial.org/files/?artifact_id=14416),

/If the dimensional quantity has no units (e.g. band number in a
multi-wavelength sensor), use the null string:units=""./

so I think GeoServer should follow the Specification and allow using
dimension that has no units.

--
Sent from: http://osgeo-org.1560.x6.nabble.com/GeoServer-User-f3786390.html

Andrea_Aime4 · April 15, 2019, 2:24pm

You should open a ticket with references on how to reproduce (an caps link to an open server with the input would be useful).
Past that, check https://github.com/geoserver/geoserver/wiki/Successfully-requesting-and-integrating-fixes,-improvements-and-new-features-in-GeoServer

Cheers
Andrea

···

Regards, Andrea Aime == GeoServer Professional Services from the experts! Visit http://goo.gl/it488V for more information. == Ing. Andrea Aime @geowolf Technical Lead GeoSolutions S.A.S. Via di Montramito 3/A 55054 Massarosa (LU) phone: +39 0584 962313 fax: +39 0584 1660272 mob: +39 339 8844549 http://www.geo-solutions.it http://twitter.com/geosolutions_it ------------------------------------------------------- Con riferimento alla normativa sul trattamento dei dati personali (Reg. UE 2016/679 - Regolamento generale sulla protezione dei dati “GDPR”), si precisa che ogni circostanza inerente alla presente email (il suo contenuto, gli eventuali allegati, etc.) è un dato la cui conoscenza è riservata al/i solo/i destinatario/i indicati dallo scrivente. Se il messaggio Le è giunto per errore, è tenuta/o a cancellarlo, ogni altra operazione è illecita. Le sarei comunque grato se potesse darmene notizia. This email is intended only for the person or entity to which it is addressed and may contain information that is privileged, confidential or otherwise protected from disclosure. We remind that - as provided by European Regulation 2016/679 “GDPR” - copying, dissemination or use of this e-mail or the information herein by anyone other than the intended recipient is prohibited. If you have received this email by mistake, please notify us immediately by telephone or e-mail.

Seib_Jurgen · April 15, 2019, 2:30pm

Dear Rayman,

OGC developed a "Best Practice for using Web Map Services (WMS) with Time-Dependent or Elevation-Dependent Data" (https://portal.opengeospatial.org/files/?artifact_id=56394) . This document requires that "Conformant WMS servers SHALL declare in each elevation dimension of the Capabilities document the attribute UNITS and assign it a CRS identifier specifying the vertical CRS. Elevation metric values SHALL be expressed in units of the CRS." (see page 26 of the best practice document)

Unfortunately, your external WMS server is not conformant to this OGC best practice. It is debatable whether GeoServer should allow the empty string for the 'units' attribute of an elevation dimension.

Kind regards,
Jürgen

-----------------------------------
Dr. Jürgen Seib
Deutscher Wetterdienst
TI1/K - IT-Koordination
Frankfurter Strasse 135
63067 Offenbach
Tel.: +496980622609
EMail: juergen.seib@anonymised.com

-----Ursprüngliche Nachricht-----
Von: Rayman [mailto:touhourayman@anonymised.com]
Gesendet: Samstag, 13. April 2019 15:05
An: geoserver-users@lists.sourceforge.net
Betreff: [Geoserver-users] GeoServer should allow WMS to use dimension without units

Hi
I am using GeoServer to add a external WMS server, but it failed because
GeoServer throw below error

13 Apr 18:37:49 ERROR [data.ows] - Failed to execute request
https://nomads.ncdc.noaa.gov/thredds/wms/gfs-004-anl/201809/20180916/gfsanl_4_20180916_0000_000.grb2?REQUEST=GetCapabilities&VERSION=1.3.0&SERVICE=WMS
13 Apr 18:38:24 ERROR [geotools.xml] - Dimension element contains no 'units'
attribute

The capabilities xml in above URL contains below dimension

It has a empty units, but according to the Web Map Service Implementation
Specification Section
C.2(http://portal.opengeospatial.org/files/?artifact_id=14416),

/If the dimensional quantity has no units (e.g. band number in a
multi-wavelength sensor), use the null string:units=""./

so I think GeoServer should follow the Specification and allow using
dimension that has no units.

--
Sent from: http://osgeo-org.1560.x6.nabble.com/GeoServer-User-f3786390.html

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Rayman · April 16, 2019, 12:48am

Hi Jürgen,

Thanks for letting know the best practice, now I know the elevation
dimension should have units.
I think I should contact the maintainer of the WMS server to modify the
Capabilities document, but before that I have a question: Does GeoServer
force all dimensions to have non-empty units?

If I change "<Dimension name="elevation" units="" default="0.995">" to
"<Dimension name="sigma" units="" default="0.995">", will GeoServer still
throw a error?

--
Sent from: http://osgeo-org.1560.x6.nabble.com/GeoServer-User-f3786390.html

Andrea_Aime4 · April 16, 2019, 1:44pm

GeoServer is typically very tolerant with inputs, it has never played “OGC Cop”, not by default at least.
A code change that allows it to work with misconfigured units would be welcomed, maybe with a flag to turn it off and have strict behavior

Cheers
Andrea

···

GeoServer Professional Services from the experts! Visit http://goo.gl/it488V for more information. == Ing. Andrea Aime @geowolf Technical Lead GeoSolutions S.A.S. Via di Montramito 3/A 55054 Massarosa (LU) phone: +39 0584 962313 fax: +39 0584 1660272 mob: +39 339 8844549 http://www.geo-solutions.it http://twitter.com/geosolutions_it ------------------------------------------------------- Con riferimento alla normativa sul trattamento dei dati personali (Reg. UE 2016/679 - Regolamento generale sulla protezione dei dati “GDPR”), si precisa che ogni circostanza inerente alla presente email (il suo contenuto, gli eventuali allegati, etc.) è un dato la cui conoscenza è riservata al/i solo/i destinatario/i indicati dallo scrivente. Se il messaggio Le è giunto per errore, è tenuta/o a cancellarlo, ogni altra operazione è illecita. Le sarei comunque grato se potesse darmene notizia. This email is intended only for the person or entity to which it is addressed and may contain information that is privileged, confidential or otherwise protected from disclosure. We remind that - as provided by European Regulation 2016/679 “GDPR” - copying, dissemination or use of this e-mail or the information herein by anyone other than the intended recipient is prohibited. If you have received this email by mistake, please notify us immediately by telephone or e-mail.