Re: Meeting about improving the GRD API.

Ian Barrodale wrote:

> Hi All:
>
> Based on your feedback (John and Ted), we've been talking and have
> an interesting project idea - brought up today by Peter.
>
> If we were able to put GRD database support into the Java netCDF
> library and use THREDDS and TDS to serve data, we may 
> also be able to provide gridded data reprojection support.
>  
> What do  you think of this idea please?   Some details follow below.
>
> If a grd:// URL was allowed to contain a bit of spatial reference text
> so that not only did it specify the database server, login info, database
> name, and variable name, but also the projection and its parameters
> (sort of like an OPeNDAP subset specification) then the GRD could
> reproject any of the gridded data (including satellite swath data such
> as from a POES satellite) to a projection of the user's choice.  The
> spatial reference text could be tacked onto the grd:// URL in the records
> returned by THREDDS according to some number of pre-specified
> projections that we create. 
>
> Such a capability would help to support users like Dave Foley and
> Roy Mendelssohn (copied) who have expressed an interest to us in storing 
> unmapped satellite data in a spatial database, as well as other 
> groups such as the NOAA/NESDIS CLASS archive.  According to Peter,
> the NOAA CoastWatch technical group has been talking for years about
> how nice it would be to be able to pull unmapped satellite data out of 
> CLASS
> in a user- specified projection rather than having to create mapped 
> products.
>
> Have a great weekend.
>
> Regards,
> Ian
> =====================
Its a very interesting possibility. The core question is, how does the 
user specify the reprojection?

The netcdf data model doesnt allow for modifying the dataset based on 
user input. If there were a small set of possible projections, one could 
create a dataset for each possibilty, but this doesnt scale. So its 
important to realize that this capability takes us into extensions of 
the data model.

OPeNDAP has "server side functions", which would allow you to specify 
the reprojection, but theres no standard way to do this AFAIK, so we'd 
be creating one.

WCS does have standard reprojection capabilities, and this is the 
obvious path. But can any of the client software already talk to WCS 
servers? The WCS messaging XML is somewhat complicated to learn.

One  could also create a simpler REST based web service for this capability.

So the immediate question in my mind is what clients would use this 
capability, and how will they specify it.