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netCDF questions...

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  • Subject: netCDF questions...
  • Date: Mon, 20 Jun 1994 16:46:32 -0600
>From: address@hidden (Rob -Not from Bloom County- Binkley, EIT)
>Organization: NASA Dryden FRC
>Keywords: 199406180327.AA22869 netCDF

Rob,

>I have been tasked with building a data recording system
>t record PCM streams and RADAR data from research flights
>and for our flight simulation labs.  I am currently
>re-evaluating the format to store the recorded data.
>We currently use a "home-brew" format, which has many
>limitations, among which is fortran-only support.
>
>I was looking at netCDF and HDF as possible alternative
>formats, but I have a few questions.
>
>IS netCDF a viable format for recording data direct to
>disk as it comes down a PCM stream?  

I am not familiar with the term PCM stream.  The netCDF gives a library
of functions for manipulating netCDF files.  These files are randomly
accessible.  The major slowness you will find in reading/writing netCDF
is the layer that passes variables throught XDRs before reads/writes.

>After the file is initalized, is sequential writes to the file of
>new "frames" of time-tagged data independant of file size?

A seek has to be done to get to the correct data location, so writes are
not instantaneous.

>(I will be writing about 500,000 parameters/sec.)

The comment on XDR above.

>Thanks for any help that you may be able to give,

You might want to grab the netcdf package, build it, play around with
some examples and build an application that mimics the flood of data that
you will be receiving.  You should then be able to determine if you can
handle the PCM stream that you asked about.

Tom Yoksas