[thredds] Height subsetting for NetCDF Subset Service (NCSS)

• To: support-thredds@xxxxxxxxxxxxxxxx, THREDDS community <thredds@xxxxxxxxxxxxxxxx>
• Subject: [thredds] Height subsetting for NetCDF Subset Service (NCSS)
• From: Rich Signell <rsignell@xxxxxxxx>
• Date: Sun, 27 Mar 2011 15:06:23 -0400

TDS Developer Gurus,

The NetCDF Subset Service (NCSS) in TDS is great for people who just
want to extract part of a dataset and save it locally as a NetCDF
file.  It's great to be able to subset by lon/lat values and time
(X,Y,T), but how about also adding the ability to subset by
height/depth (Z)?

A common use case in oceanography is that folks just need the surface
layer currents from a model with many vertical layers  to track things
that stay at the surface (oil, larvae, search & rescue, etc).

So it would be great if, for example, one could use NCSS to extract
just the surface layer (Depth: z=0) from this dataset:
<http://edac-dap3.northerngulfinstitute.org/thredds/ncss/grid/ncom_useast_agg/US_East_Aggregation_best.ncd/dataset.html>
instead of being forced to get all 40 layers!

As additional minor suggestions for the NCSS GUI, I think the
interface would benefit by

1) dropping the "all" radio buttons from the "Choose Spatial Subset"
and "Choose Time Subset" selections.   The service already populates
the bounding box and start/stop times with the min/max extents of the
spatial and time coordinates, so just leaving the limits alone would
give you "all".   I've seen several users change the limits to subset,
but forget to change the radio button from "all" to "subset", and then
have the request fail because they asked for too much data by mistake,
not realizing that the subset values they typed in were not activated.

2) turning "on" by default the "add Lon/Lat to file".    Most people
want  the coordinate variables!  Not sure why there is an option to
leave off (by default even!) the lon/lat (X,Y) coordinate variables,
when there is no option to leave off the time (T) and depth (Z)
variables.

3) Put a "1" in the "Horizontal Stride" box by default instead of
leaving it empty.

4) Add a "Time Stride" box, and give it a default value of "1".

5) Add a "Height Stride" box, and give it a default value of "1".

I guess that's enough suggestions for now.   ;-)

Thanks,
Rich
-- 
Dr. Richard P. Signell   (508) 457-2229
USGS, 384 Woods Hole Rd.
Woods Hole, MA 02543-1598