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Programming > Idl-pvware > Re: HDF_SD_ADDD...
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Re: HDF_SD_ADDDATA problem

by James Kuyper <jameskuyper@[EMAIL PROTECTED] > Apr 28, 2008 at 02:52 AM

adfraser@[EMAIL PROTECTED]
 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.




 20 Posts in Topic:
HDF_SD_ADDDATA problem
adfraser@[EMAIL PROTECTED  2008-04-21 16:24:17 
Re: HDF_SD_ADDDATA problem
"brodzik@[EMAIL PROT  2008-04-22 07:23:38 
Re: HDF_SD_ADDDATA problem
"brodzik@[EMAIL PROT  2008-04-22 07:25:50 
Re: HDF_SD_ADDDATA problem
UV_Catastrophe <bripma  2008-04-22 13:57:56 
Re: HDF_SD_ADDDATA problem
adfraser@[EMAIL PROTECTED  2008-04-23 19:17:22 
Re: HDF_SD_ADDDATA problem
adfraser@[EMAIL PROTECTED  2008-04-23 19:18:31 
Re: HDF_SD_ADDDATA problem
adfraser@[EMAIL PROTECTED  2008-04-23 19:23:27 
Re: HDF_SD_ADDDATA problem
jameskuyper@[EMAIL PROTEC  2008-04-24 06:00:58 
Re: HDF_SD_ADDDATA problem
"brodzik@[EMAIL PROT  2008-04-24 07:25:39 
Re: HDF_SD_ADDDATA problem
jameskuyper@[EMAIL PROTEC  2008-04-25 09:15:05 
Re: HDF_SD_ADDDATA problem
liamgumley@[EMAIL PROTECT  2008-04-25 09:18:25 
Re: HDF_SD_ADDDATA problem
adfraser@[EMAIL PROTECTED  2008-04-27 18:05:57 
Re: HDF_SD_ADDDATA problem
adfraser@[EMAIL PROTECTED  2008-04-27 18:08:32 
Re: HDF_SD_ADDDATA problem
James Kuyper <jameskuy  2008-04-28 02:52:31 
Re: HDF_SD_ADDDATA problem
jameskuyper@[EMAIL PROTEC  2008-04-28 16:07:27 
Re: HDF_SD_ADDDATA problem
adfraser@[EMAIL PROTECTED  2008-04-29 22:57:17 
Re: HDF_SD_ADDDATA problem
James Kuyper <jameskuy  2008-04-30 11:13:39 
Re: HDF_SD_ADDDATA problem
adfraser@[EMAIL PROTECTED  2008-04-29 23:43:34 
Re: HDF_SD_ADDDATA problem
James Kuyper <jameskuy  2008-04-30 11:20:11 
Re: HDF_SD_ADDDATA problem
adfraser@[EMAIL PROTECTED  2008-05-01 19:05:51 

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tan12V112 Fri May 16 7:16:07 CDT 2008.