Subject: Re: Speaking of numerical data...

From: [email-masked] (Marty Ryba)
Date: Fri, 4 Jun 93 17:02:45 GMT

In article <[email-masked]>, [email-masked] (Ken Stone) writes:
|>   Does HDF support numerical data, such as a time series, as opposed to 
|> images?  
|> 
|>   For example,  consider geophysical measurements taken from an aircraft
|> flight.  The data set contains a time series of locations (lat,lon,altitude) 
|> and 10 different chemical concentrations at each time/location.  Basically a 
|> time series with 13 parameters.  Is this something that HDF will handle 
|> easily? 
|> -- 
|> Ken Stone                  
|> NASA LaRC -- GATS, Inc.     
|> Hampton VA                   

    I would use netCDF.  Not to get into a flame war, but having tried
HDF, I'd say that time series data is not one of its strong points.  (net)CDF
allows you to continually append new data points and allows practically
random-access retrieval of such.  I recommend it.

-- 
Dr. Marty Ryba                     | Generation X:
MIT Lincoln Laboratory             |        Too young to be cynical,
[email-masked]                    |		too old to be optimistic.
Of course nothing I say here is official policy!!!!

---

From: [email-masked] (James L. Anderson)
Date: 17 Jun 1993 15:46:16 GMT

In article <[email-masked]>, [email-masked] (Roger
D Ray) wrote:
> 
> > In article <[email-masked]>, [email-masked] (Ken
> > Stone) wrote:
> > > 
> > >   Does HDF support numerical data, such as a time series, as opposed to 
> > > images?  
> > > 
> > >   For example,  consider geophysical measurements taken from an aircraft
> > > flight.  The data set contains a time series of locations (lat,lon,altitude) 
> > > and 10 different chemical concentrations at each time/location.  Basically a 
> > > time series with 13 parameters.  Is this something that HDF will handle 
> > > easily? 
> > 

I have been using the HDF scientific data sets (SDS) for storage,
transport,
display, and analysis of time series data for several years.  I originally
set up the files with a rank=2, 2 columns of data with the first column the
time 
channel and second the data channel.  Each data channel was a separate SDS.
However, this resulted in file sizes twice as large as required.  Although
it is
not documented, an SDS can be written with a rank=1.  My current file
format is to have the first SDS in the file contain the time channel, and
the subsequent
SDSs containing the individual data channels.  I have used this format with
up to 200 channels with about 20,000 data points per channel.  I do most of
my 
data processing/presentation on a Macintosh and have written a graphics
plotting
program to read the HDF file and plot the data.  If anyone is interested in
this
technique I can provide information.

James L. Anderson
Idaho National Engineering Laboratory
POB 1625   MS:3895
Idaho Falls, ID 83415

Internet: [email-masked]