Re: [thredds] Incorrect values for elevation (WMS)

• To: THREDDS THREDDS <thredds@xxxxxxxxxxxxxxxx>
• Subject: Re: [thredds] Incorrect values for elevation (WMS)
• From: Pauline Mak <Pauline.Mak@xxxxxxxxxxx>
• Date: Tue, 20 Jul 2010 08:46:57 +1000

Hi Ethan,

Yes!  It does indeed have an attribute of:

positive: "down"

So should we convert values (and metadata) to have positive values going up?

Cheers,

-Pauline.

On 20/07/10 1:48 AM, Ethan Davis wrote:

Hi Pauline,

Does the zt_ocean variable have a "positive" attribute with a value of
"down"?

      zt_ocean:positive = "down" ;

If so, then the WMS may be converting the values so that positive Z is
upwards.

Ethan

On 7/18/2010 11:19 PM, Pauline Mak wrote:

Hi all,

I've found some problems with how the WMS servlet shows elevation values.

We have a NetCDF file with these values in it (using the OPeNDAP ASCII
response):

zt_ocean[47]
5.0, 15.0, 25.0, 35.0, 45.0, 55.0, 65.0, 75.0, 85.0, 95.0, 105.0, 115.0,
125.0, 135.0, 145.0, 155.0, 165.0, 175.0, 185.0, 195.0, 205.0,
216.50769, 232.35658, 254.85658, 285.51538, 324.8566, 372.3566,
426.50772, 485.00003, 545.0, 609.0192, 684.0192, 774.0192, 879.0192,
995.0, 1115.0, 1237.4758, 1366.8885, 1506.3256, 1656.8885, 1817.4758,
1985.0, 2155.0, 2404.449, 2861.898, 3576.449, 4499.0

However, in the WMS GetCapabilities document, the elevation values are
shown like so:

<Dimension name="elevation" units="meters" default="-5.0">
-5.0,-15.0,-25.0,-35.0,-45.0,-55.0,-65.0,-75.0,-85.0,-95.0,-105.0,-115.0,-125.0,-135.0,-145.0,-155.0,-165.0,-175.0,-185.0,-195.0,-205.0,-216.5076904296875,-232.35658264160156,-254.85658264160156,-285.515380859375,-324.8565979003906,-372.3565979003906,-426.5077209472656,-485.0000305175781,-545.0,-609.0192260742188,-684.0192260742188,-774.0192260742188,-879.0192260742188,-995.0,-1115.0,-1237.475830078125,-1366.8885498046875,-1506.3255615234375,-1656.8885498046875,-1817.475830078125,-1985.0,-2155.0,-2404.448974609375,-2861.89794921875,-3576.448974609375,-4499.0

</Dimension>

The values are float32s:

Float32 zt_ocean[zt_ocean = 47];

So it looks like there's some precision problems?

I am using TDS Version 4.2.20100607.1833 - 20100607.1833

Cheers,

-Pauline.

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Pauline Mak
AODN-DO
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• References:
  • [thredds] Incorrect values for elevation (WMS)
    • From: Pauline Mak
  • Re: [thredds] Incorrect values for elevation (WMS)
    • From: Ethan Davis