| Re: reading and importing EOS-HDF [message #66772] |
Tue, 09 June 2009 07:24 |
jameskuyper
Messages: 79
Registered: October 2007
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Member |
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David Fanning wrote:
> Maarten writes:
>
>> HDF-EOS-2 (based on HDF-4) is fully supported in IDL, see the
>> documentation for the eos_pt_*, eos_gd_* and eos_sw_* routines in the
>> online help. These routines are failrly high-level, although the
>> calling order can be somewhat odd (especially when writing data to a
>> file).
>
> Humm. I guess my definition of "high-level" must be different
> from yours. Nevertheless, I find this alphabetical listing of
> routines you *could* use if you knew what the hell you were
> doing (which you don't) to be totally off-putting and
> depressing. Since years of IDL experience doesn't seem to
> help get through the morass, I can only imagine what I would
> think if I were approaching it as an IDL novice. "Matlab",
> probably. :-(
You might find the information available at <http://hdfeos.org/docs.php>
helpful. It doesn't document the IDL wrappers for the HDF-EOS routines,
but if you know the name of the appropriate C routine, it's usually not
too difficult to locate the corresponding IDL routine.
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| Re: reading and importing EOS-HDF [message #66774 is a reply to message #66772] |
Tue, 09 June 2009 06:04  |
Maarten[1]
Messages: 176
Registered: November 2005
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Senior Member |
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On Jun 9, 2:39 pm, David Fanning <n...@dfanning.com> wrote:
> Maarten writes:
>> HDF-EOS-2 (based on HDF-4) is fully supported in IDL, see the
>> documentation for the eos_pt_*, eos_gd_* and eos_sw_* routines in the
>> online help. These routines are failrly high-level, although the
>> calling order can be somewhat odd (especially when writing data to a
>> file).
>
> Humm. I guess my definition of "high-level" must be different
> from yours.
It is a matter of gradation. The hdf-5 routines are mostly god-awful,
while the hdf-eos2 routines almost make sense. Part of my experience
is with the C-interface, which IDL follows a little to closely for
comfort. In the C-world, the difference is even more remarkable.
> Nevertheless, I find this alphabetical listing of
> routines you *could* use if you knew what the hell you were
> doing (which you don't) to be totally off-putting and
> depressing.
Agreed, there are things you could do with your time that are more
fun. Still, the eos_sw_* interface isn't totally bogus (open file,
open swath, read data, close swath, close file - makes sense to me).
The eos_gd_* interface has too many options for defining the grid, I
hope your files don't use the most exotic ones.
> Since years of IDL experience doesn't seem to
> help get through the morass, I can only imagine what I would
> think if I were approaching it as an IDL novice. "Matlab",
> probably. :-(
Python, especially if you have to deal with hdf-5. PyTables is the
best interface for HDF-5 on any platform I've used.
> P.S. I do find it immensely cheering that things are
> "fully supported" though. ;-)
For HDF-EOS-2: you can at least create files that are compliant,
something that is impossible with HDF-EOS-5, although you can fake
things to fool most software.
Maarten
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| Re: reading and importing EOS-HDF [message #66775 is a reply to message #66774] |
Tue, 09 June 2009 05:39 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Maarten writes:
> HDF-EOS-2 (based on HDF-4) is fully supported in IDL, see the
> documentation for the eos_pt_*, eos_gd_* and eos_sw_* routines in the
> online help. These routines are failrly high-level, although the
> calling order can be somewhat odd (especially when writing data to a
> file).
Humm. I guess my definition of "high-level" must be different
from yours. Nevertheless, I find this alphabetical listing of
routines you *could* use if you knew what the hell you were
doing (which you don't) to be totally off-putting and
depressing. Since years of IDL experience doesn't seem to
help get through the morass, I can only imagine what I would
think if I were approaching it as an IDL novice. "Matlab",
probably. :-(
Cheers,
David
P.S. I do find it immensely cheering that things are
"fully supported" though. ;-)
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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| Re: reading and importing EOS-HDF [message #66778 is a reply to message #66775] |
Tue, 09 June 2009 02:08 |
Maarten[1]
Messages: 176
Registered: November 2005
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Senior Member |
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On Jun 9, 8:01 am, drgur...@icimod.org wrote:
> I am very new to IDL and trying to read/import EOS-HDF. Any
> references, tutorials and guidance much appreciated.
Which version of HDF-EOS, or from which instrument or dataset?
HDF-EOS-2 (based on HDF-4) is fully supported in IDL, see the
documentation for the eos_pt_*, eos_gd_* and eos_sw_* routines in the
online help. These routines are failrly high-level, although the
calling order can be somewhat odd (especially when writing data to a
file).
HDF-EOS-5 (yes, based on HDF-5) has no special routines available in
IDL, here you'll need to use the plain HDF-5 routines. Although a
little more sanitized when compared to the HDF-4 routines, these are
still low level routines. Over at [1] you'll find some instructions
for HDF-(EOS-)5, in this case for the OMI (EOS-Aura) project.
I suggest that you at least install HDFView [2]. This tool allows you
to inspect all variants of HDF files, and is a great aid in finding
which field you actually want to read.
Best,
Maarten
[1] http://www.knmi.nl/omi/research/product/read_tool_omi_level2 .php
[2] http://www.hdfgroup.org/hdf-java-html/hdfview/
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