Hello all,
I'm new to this mailing list but not new to netCDF and I have a few
things I'm interested in discussing with other netCDF users. First, I'm
currently working on the next major release of NCAR Graphics. For those not
familiar with NCAR Graphics send me your address and I will arainge to have some
info sent to you. Anyways, the next major release of NCARG will have interactive
capabilities, such as a GUI for selection of data and specificatoin of viewing
parameters. I've found that one can not plan for interactive graphics with
out considering interactive data manipulation, selection and sequencing. To
handle these requirements I am designing a scripting language called the NCAR
Command Language (NCL).
NCL is an interpreted language that provides a uniform environment for reading
data, manipulating and tranforming the data, specifing visualizations styles,
rendering of the visualizations and allowing the user to return to any of the
previous steps at anytime. For those familiar with IDL, NCL is similar but I
find that some of IDL's data management and language syntax leaves alot to be
desired. Furthermore, IDL doesn't, IMHO, easily allow their users to produce
publication quality graphics.
I have addopted the netCDF data model as the internal model of data in NCL. I
have not found other formats, that represent scientific data, that do not map
into the netCDF model. The main data type is the file record (netCDF file). The
file record has all of the features of the netCDF file, file attributes,
variables, named dimensions, variable attributes, etc ... The following is an
example script from the prototype that I have already implemented. It loads
a file called "temp", displays the contents of the file and converts the
temperature from celcius to farenheit for every forecast time, longitude,
latitude, and only the first four elements of the level dimension and then
writes the a new file called "temp_faren.cdf":
Script started on Thu Jan 9 17:13:39 1992
conundrum[1] ncl
ncl> addfile("temp.cdf")
ncl> inquire
FILE VARIABLE DIMENSION DIM NAMES
-------------------------------------------------------------------------------
temp.cdf grib_model 8X10
temp.cdf grib_center 8X10
temp.cdf reftime 20
temp.cdf level 10
temp.cdf frtime 8
temp.cdf lon 36
temp.cdf lat 33
temp.cdf T 8X10X33X36
ncl> faren = temp.T[*][0:3] * 9 / 5 + 32
FileRead
reading 152064 bytes. Please wait...read succesful
ncl> writer("/u1/ethan/faren.cdf",faren,"temp_faren")
Write 152064 bytes ...Write Succesful
ncl> quit
conundrum[2]
script done on Thu Jan 9 17:17:05 1992
This is a very crude example and does not outline the planned capabilities but
it does demonstrate how powerful and easy to use a language like this can be.
Well the functional specification will be complete for this language within the
next few weeks and I'm looking for individuals to review the document and make
sure that its actually going to be usable. Individuals who have meaningful
comments and critisisms of the functional spec will be considered for early
alpha and beta testing.
If you are interested please send me some email. By providing your input on
this project you are helping to specify a tool that could help meet some of
your computing needs and the needs of the atmospheric science community.
The description I have given here is very brief so if you have any immediate
questions please feel free to contact me.
Thank you for your time,
ethan
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Ethan Alpert ethan@xxxxxxxxxxxxx
NCAR Interactive Project Coordinator
Scientific Visualization Group
Scientific Computing Division
National Center for Atmospheric Research
PO BOX 3000, Boulder Co, 80307-3000
Ph# (303)497-1832
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