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[THREDDS #CEF-295275]: WMS 1.3 Black image return

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  • Subject: [THREDDS #CEF-295275]: WMS 1.3 Black image return
  • Date: Tue, 12 Nov 2019 11:19:25 -0700
Greetings!

As far as I can tell, this appears to be due to a change in the EPSG database 
conventions used in WMS 1.3 (related to the order of latitude / longitude
coordinates). See the response by Jon Blower, the lead developer of ncWMS,
to a similar issue:

https://www.unidata.ucar.edu/mailing_lists/archives/thredds/2013/msg00171.html

If I edit the 1.3 request to use CRS:84, I get an image:

http://dap.saeon.ac.za/thredds/wms/SAEON.SAWS/fig9c.nc?service=WMS&version=1.3.0&request=GetMap&layers=tas&styles=boxfill/rainbow&bbox=13.199999809265137,-35.63999938964844,34.7599983215332,-20.239999771118164&width=768&height=552&crs=CRS:84&format=image/png&ELEVATION=0

If I add back in a color range similar to the 1.1 request, then things match
up as expected:

http://dap.saeon.ac.za/thredds/wms/SAEON.SAWS/fig9c.nc?service=WMS&version=1.3.0&request=GetMap&layers=tas&TRANSPARENT=true&STYLES=boxfill/rainbow&COLORSCALERANGE=0,5&NUMCOLORBANDS=20&bbox=13.199999809265137,-35.63999938964844,34.7599983215332,-20.239999771118164&width=768&height=552&crs=CRS:84&format=image/png&ELEVATION=0

Cheers,

Sean

> Good day
> 
> I've been testing the WMS capabilities of THREDDS and have been trying to
> call an image from the WMS 1.3 on our server, here is an example of a
> sample call:
> 
> http://dap.saeon.ac.za/thredds/wms/SAEON.SAWS/fig9c.nc?service=WMS&version=1.3.0&request=GetMap&layers=tas&styles=boxfill/rainbow&bbox=13.199999809265137,-35.63999938964844,34.7599983215332,-20.239999771118164&width=768&height=552&crs=EPSG:4326&format=image/png&ELEVATION=0
> 
> This returns a black image, which I've heard is the case with other thredds
> users. If I use the call using the WMS 1.1 with the following call:
> 
> http://dap.saeon.ac.za/thredds/wms/SAEON.SAWS/fig9b.nc?LAYERS=tas&ELEVATION=0&TIME=2095-12-31T12%3A00%3A00.000Z&TRANSPARENT=true&STYLES=boxfill%2Frainbow&COLORSCALERANGE=0%2C5&NUMCOLORBANDS=20&LOGSCALE=false&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&FORMAT=image%2Fpng&SRS=EPSG%3A4326&BBOX=13.199999809265,-35.639999389648,34.759998321533,-20.239999771118&WIDTH=500&HEIGHT=500
> 
> I get an image back consistent with the data. Is there any reason for the
> discrepancy?
> 
> 
> Many Thanks
> --

Ticket Details
===================
Ticket ID: CEF-295275
Department: Support THREDDS
Priority: Normal
Status: Open
===================
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