Yes, it's crazy. I'm surprised that EPSG:4326 isn't officially deprecated
(perhaps it is and I don't know!). We'll be living with the confusion for
years to come I'm sure.
The FAQ entry on the ncWMS website (linked below) contains a useful tip for
manipulating the behaviour of OpenLayers in this regard, which may be useful to
some.
Jon
From: bennoblumenthal@xxxxxxxxx [mailto:bennoblumenthal@xxxxxxxxx] On Behalf Of
Benno Blumenthal
Sent: 15 April 2013 20:36
To: John Maurer
Cc: Jon Blower; ncwms-users@xxxxxxxxxxxxxxxxxxxxx; THREDDS Users
Subject: Re: [thredds] [Ncwms-users] WMS 1.3.0 blank maps using EPSG:4326 (but
works using CRS:84)
Keep in mind that Jon said that the code now correctly implements the 1.3
standard, not that the standard makes any sense. Interpreting 'x' and 'y' as
'the order one prints the pair of coordinates in' was an extremely poor choice
by the committee, especially since it was different in 1.1. To use 1.3
correctly, the code has to know what order the coordinates are for each
projection, more or less impossible to code without a kludge or a projection
database standard API.
On Mon, Apr 15, 2013 at 3:32 PM, John Maurer
<jmaurer@xxxxxxxxxx<mailto:jmaurer@xxxxxxxxxx>> wrote:
Thanks, all! I'm surprised the ordering of coordinates changes with projection,
but I can work with that! I appreciate your responses.
Cheers,
John (Maurer)
On Mon, Apr 15, 2013 at 12:01 AM, Jon Blower
<j.d.blower@xxxxxxxxxxxxx<mailto:j.d.blower@xxxxxxxxxxxxx>> wrote:
> for some unfathomable reason the spec switches to ymin,xmin,ymax,xmax in
> 1.3.0 when you use CRS:84
I think you mean "... when you use EPSG:4326". CRS:84 is always x,y axis
order. ;-)
The reason is that the EPSG database uses conventions from navigation, which is
latitude-longitude order. There was a mistake in WMS1.1.1 that meant that
EPSG:4326 was defined with the axis order reversed. This was corrected in WMS
1.3.0 and a new CRS added (CRS:84) that is defined with longitude-latitude axis
order.
Thanks for those links Ivan, very helpful!
Jon
From: Ivan Price [mailto:Ivan.Price@xxxxxxxxxxx<mailto:Ivan.Price@xxxxxxxxxxx>]
Sent: 15 April 2013 10:18
To: John Maurer; THREDDS Users;
ncwms-users@xxxxxxxxxxxxxxxxxxxxx<mailto:ncwms-users@xxxxxxxxxxxxxxxxxxxxx>
Subject: Re: [Ncwms-users] [thredds] WMS 1.3.0 blank maps using EPSG:4326 (but
works using CRS:84)
it could be the order of lat/longs is reversed in your request.
for some unfathomable reason the spec switches to ymin,xmin,ymax,xmax in 1.3.0
when you use CRS:84
see this:
http://viswaug.wordpress.com/2009/03/15/reversed-co-ordinate-axis-order-for-epsg4326-vs-crs84-when-requesting-wms-130-images/
or ncWMS specifically this:
http://www.resc.rdg.ac.uk/trac/ncWMS/wiki/FrequentlyAskedQuestions#MyWMSclientuseslatitude-longitudeaxisorder
so your initial link works if you swap them around...
http://oos.soest.hawaii.edu/thredds/wms/hioos/roms_forec_regridded/hiig/ROMS_Hawaii_Regional_Ocean_Model_Regridded_best.ncd?service=WMS&version=1.3.0&REQUEST=GetMap&FORMAT=image/png&TRANSPARENT=true&LAYERS=water_temp&CRS=EPSG:4326&BBOX=20.17714549791179,202.12371826171875,21.50418550077842,204.46517944335938&WIDTH=1705&HEIGHT=1034&TIME=2013-04-15T00:00:00Z&ELEVATION=-5&STYLES=boxfill/rainbow&NUMCOLORBANDS=256&COLORSCALERANGE=24.02441,26.03417
-i
De : thredds-bounces@xxxxxxxxxxxxxxxx<mailto:thredds-bounces@xxxxxxxxxxxxxxxx>
[mailto:thredds-bounces@xxxxxxxxxxxxxxxx] De la part de John Maurer
Envoyé : Saturday, 13 April 2013 02:46
À : THREDDS Users;
ncwms-users@xxxxxxxxxxxxxxxxxxxxx<mailto:ncwms-users@xxxxxxxxxxxxxxxxxxxxx>
Objet : [thredds] WMS 1.3.0 blank maps using EPSG:4326 (but works using CRS:84)
Hi TDS and/or ncWMS folks,
I recently upgraded from TDS 4.2.10 to 4.3.16 and am noticing something strange
in my WMS output. GetMap URL's that used to work fine in TDS 4.2.10 are coming
up blank in 4.3.16. As a workaround, I discovered that changing my CRS from
EPSG:4326 to CRS:84 fixes the problem. Seems like a bug with using EPSG:4326??
Here's an example using a ROMS ocean forecast of water temperature over central
Hawaii. Using EPSG:4326 gives a blank map:
http://oos.soest.hawaii.edu/thredds/wms/hioos/roms_forec_regridded/hiig/ROMS_Hawaii_Regional_Ocean_Model_Regridded_best.ncd?service=WMS&version=1.3.0&REQUEST=GetMap&FORMAT=image/png&TRANSPARENT=true&LAYERS=water_temp&CRS=EPSG:4326&BBOX=202.12371826171875,20.17714549791179,204.46517944335938,21.50418550077842&WIDTH=1705&HEIGHT=1034&TIME=2013-04-15T00:00:00Z&ELEVATION=-5&STYLES=boxfill/rainbow&NUMCOLORBANDS=256&COLORSCALERANGE=24.02441,26.03417
In contrast, if I switch this to CRS:84 I now get a color map as expected:
http://oos.soest.hawaii.edu/thredds/wms/hioos/roms_forec_regridded/hiig/ROMS_Hawaii_Regional_Ocean_Model_Regridded_best.ncd?service=WMS&version=1.3.0&REQUEST=GetMap&FORMAT=image/png&TRANSPARENT=true&LAYERS=water_temp&CRS=CRS:84&BBOX=202.12371826171875,20.17714549791179,204.46517944335938,21.50418550077842&WIDTH=1705&HEIGHT=1034&TIME=2013-04-15T00:00:00Z&ELEVATION=-5&STYLES=boxfill/rainbow&NUMCOLORBANDS=256&COLORSCALERANGE=24.02441,26.03417
Oh... And I just found another workaround. If I switch to WMS 1.1.1 instead of
1.3.0, EPSG:4326 also works:
http://oos.soest.hawaii.edu/thredds/wms/hioos/roms_forec_regridded/hiig/ROMS_Hawaii_Regional_Ocean_Model_Regridded_best.ncd?service=WMS&version=1.1.1&REQUEST=GetMap&FORMAT=image/png&TRANSPARENT=true&LAYERS=water_temp&SRS=EPSG:4326&BBOX=202.12371826171875,20.17714549791179,204.46517944335938,21.50418550077842&WIDTH=1705&HEIGHT=1034&TIME=2013-04-15T00:00:00Z&ELEVATION=-5&STYLES=boxfill/rainbow&NUMCOLORBANDS=256&COLORSCALERANGE=24.02441,26.03417
In short, I'm hoping that somebody can fix the WMS so that EPSG:4326 will not
give me blank maps in WMS 1.3.0, but I have workarounds in the meantime so it's
not pressing.
Thanks!,
John Maurer
Pacific Islands Ocean Observing System (PacIOOS)
University of Hawaii at Manoa
_______________________________________________
thredds mailing list
thredds@xxxxxxxxxxxxxxxx<mailto:thredds@xxxxxxxxxxxxxxxx>
For list information or to unsubscribe, visit:
http://www.unidata.ucar.edu/mailing_lists/
--
Dr. M. Benno Blumenthal
benno@xxxxxxxxxxxxxxxx<mailto:benno@xxxxxxxxxxxxxxxx>
International Research Institute for climate and society
The Earth Institute at Columbia University
Lamont Campus, Palisades NY 10964-8000 (845) 680-4450
