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[THREDDS #XIG-399067]: default colorScaleRange for WMS within the TDS?

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  • Subject: [THREDDS #XIG-399067]: default colorScaleRange for WMS within the TDS?
  • Date: Fri, 04 Jun 2010 16:53:56 -0600
On 6/3/2010 2:45 AM, Jon Blower wrote:
> It's possible in the current setup to have the colour scale
> range automatically set to the min/max of the image, by using
> COLORSCALERANGE=auto (see
> http://www.resc.rdg.ac.uk/trac/ncWMS/wiki/WmsExtensions).
> However, this has two major disadvantages:
> 
> 1. The min/max values are not communicated back to the client,
> so the client doesn't know which values correspond with which
> colours.
> 2. In tiling WMS clients (where images are made up of
> individually-requested tiles) the colour scale range of each
> tile will be different.
> 
> Therefore ncWMS supports three ways of setting the colour scale
> range:
> 
> 1. COLORSCALERANGE=default, or no value set:  The default range
> for the variable is used.  This is useful for standard WMS
> clients that don't understand the ncWMS extensions.  The default
> legend uses the same colour scale range.
> 
> 2. COLORSCALERANGE=<min>,<max>: The client selects the colour
> scale range.  The Godiva2 client uses this to allow the user to
> customize the colour scaling.
> 
> 3. COLORSCALERANGE=auto, as above.  In practice, this is the
> least useful option as it's very difficult to generate an
> appropriate legend.
> 
> I agree that a layer's "ideal" default scale range will vary
> considerably with depth and time, but there's not much that can
> be done about this.  The best we can do is to set the narrowest
> range that is likely to encompass all the values in the variable.
> 
>> How often would one define a colourscalerange that doesn't match 
>> data_max/min?
> 
> The problem is finding data_min/max.  This isn't yet a standard CF
> attribute and is rarely, if ever, set.
> 
> Hope this helps,
> Jon


Ticket Details
===================
Ticket ID: XIG-399067
Department: Support THREDDS
Priority: Urgent
Status: Open