RE: redo striped.nc

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Frank Warmerdam wrote:


On 6/22/05, John Caron <caron@xxxxxxxxxxxxxxxx> wrote:

I am realizing that striped.nc also has irregularly spaced vertical
coordinates. I was thinking that didnt matter, but now im realizing that
i cant use a RectifiedGrid like the one below. Can anyone give me an
example of how it should be changed to accomodate an irregular vertical
coordinate?


To the best of my knowledge there is no GML well defined mechanism
to describe such a grid.  Please describe to the list if you find a way of
doing so.
So then we are restricted to netCDF files on uniform vertical levels, unless the server is smart enough to interpolate. But we (Unidata) have been trying to serve data as close as possible to the "real" data, so we havent been planning on adding that ability at this point.
Unless someone thinks otherwise, i will change striped.nc to be on uniform levels.
I will also send a question to the wcs email list about this. I would like to at least make sure they are considering this for WCS 1.1.
I am pleased that this has raised this question of Gaussian grids! We have rectified the grid in X-Y for our datasets, but we have abused the describeCoverage XML to explain the Z dimension as follows 
<RangeSet>
       <description>0.09999999403953552 0.19999998807907104 0.30000001192092896 0.5 
0.699999988079071 1.0 2.0 3.0 5.0 7.0 10.0 20.0 30.0 50.0 70.0 100.0 150.0 200.0 250.0 
300.0 400.0 500.0 600.0 700.0 850.0 975.0 1000.0 </description>

       <name>bands</name>
       <label>Pressure (hPa units) Levels</label>
       <axisDescription>
         <AxisDescription>
           <name>bands</name>
           <label>Bands/Channels/Samples</label>
           <values>

             <singleValue>1</singleValue>
             <singleValue>2</singleValue>
             <singleValue>3</singleValue>
             <singleValue>4</singleValue>
             <singleValue>5</singleValue>
             <singleValue>6</singleValue>

So that when you use the kvp BANDS then the client by indexing into the 
space-separated description list can calculate which
physical level this corresponds to.
This is not an ideal solution, and I welcome comments on how we can go about changing this. Rectifying the grid to evenly spaced means a change to the original dataset (though it is necessary to make geotiff). 
Hopefully this will be something that we can push into the GML in JPEG2000 
coverage format.

Norman
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