comp.lang.idl-pvwave archive: archive » HDF_SD

Home » Public Forums » archive » HDF_SD_ADDDATA problem

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: HDF_SD_ADDDATA problem [message #60155 is a reply to message #59951]

Sun, 27 April 2008 19:52

jameskuyper
Messages: 79
Registered: October 2007

Member

adfraser@utas.edu.au wrote:
> Thanks, Liam (nice book, by the way).
>
> I haven't yet investigated this, but I'd hope that the IDL routines
> are smart enough to decompress before opening the files! Actually I'm
> pretty sure they do - I can read the SDS data fine using IDL. But
> you're right, writing may be a different story. I'll check it out.

I believe that they decompress the data sets in memory; but the original
data is still in the file in compressed format, and that's what causes
the problem. The only way you can write to a compressed SDS is if it
defined as having an unlimited dimension, and the write only appends
data at the end, rather than replacing data within the SDS.

> So LAADS MODIS HDFs are HDF4, not HDF5? That's interesting.

The MODIS project standardized on HDF4 before HDF5 ever came out. HDF4
wasn't even stable yet; there's traces of bizarre workaround in some of
our code for bugs that HDF4 no longer has.

When HDF5 did come out, it was decided that with a planned instrument
lifetime of 5 years, it wasn't worthwhile going to the trouble of
switching MODIS products to HDF5. The MODIS instruments launched later
than originally planned :-( but have lasted longer than planned :-), so
the decision looks a little less reasonable now than it did at the time.
Hindsight is 20/20.

Report message to a moderator

[Message index]

		HDF_SD_ADDDATA problem By: adfraser on Mon, 21 April 2008 16:24
		Re: HDF_SD_ADDDATA problem By: brodzik@nsidc.org on Thu, 24 April 2008 07:25
		Re: HDF_SD_ADDDATA problem By: jameskuyper on Thu, 24 April 2008 06:00
		Re: HDF_SD_ADDDATA problem By: liamgumley on Fri, 25 April 2008 09:18
		Re: HDF_SD_ADDDATA problem By: adfraser on Sun, 27 April 2008 18:08
		Re: HDF_SD_ADDDATA problem By: jameskuyper on Fri, 25 April 2008 09:15
		Re: HDF_SD_ADDDATA problem By: adfraser on Sun, 27 April 2008 18:05
		Re: HDF_SD_ADDDATA problem By: adfraser on Thu, 01 May 2008 19:05
		Re: HDF_SD_ADDDATA problem By: jameskuyper on Wed, 30 April 2008 04:20
		Re: HDF_SD_ADDDATA problem By: jameskuyper on Wed, 30 April 2008 04:13
		Re: HDF_SD_ADDDATA problem By: adfraser on Tue, 29 April 2008 23:43
		Re: HDF_SD_ADDDATA problem By: adfraser on Tue, 29 April 2008 22:57
		Re: HDF_SD_ADDDATA problem By: jameskuyper on Mon, 28 April 2008 16:07
		Re: HDF_SD_ADDDATA problem By: jameskuyper on Sun, 27 April 2008 19:52

Previous Topic:	Re: IDL plotting query - how can I get rid of unwanted colour for a particular data value???
Next Topic:	Multiple draw widget events

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Fri Oct 10 14:46:31 PDT 2025

Total time taken to generate the page: 0.39921 seconds