| Re: Fill value problem in MODIS Processing... [message #54544] |
Tue, 26 June 2007 19:47  |
kim20026
Messages: 54
Registered: November 2006
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Member |
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Thank you Edward!!!
1) Sorry. Maybe the explanation for my data was not yet enough. My
mother tongue is not English, and sometimes I couldn't explain my
situation in detail. I will try one more time.
I am gathering various MODIS products overpassed near Korean peninsula
in 2003. the overpassing times of *.hdf files for this simulation are
as follows.
MOD04_L2.A2003001.0130.004.2003003124125.hdf
MOD04_L2.A2003001.0310.004.2003003134137.hdf
MOD04_L2.A2003002.0215.004.2003004030912.hdf
MOD04_L2.A2003003.0255.004.2003004220310.hdf
MOD04_L2.A2003003.0300.004.2003004220446.hdf
MOD04_L2.A2003004.0200.004.2003007020309.hdf
MOD04_L2.A2003004.0205.004.2003007020344.hdf
MOD04_L2.A2003004.0340.004.2003007023517.hdf
.
.
.
MOD04_L2.A2003360.0320.004.2003363162437.hdf
MOD04_L2.A2003361.0220.004.2003365003530.hdf
MOD04_L2.A2003362.0125.004.2003365190426.hdf
MOD04_L2.A2003362.0305.004.2003365213001.hdf
MOD04_L2.A2003363.0210.004.2004001173223.hdf
MOD04_L2.A2003363.0345.004.2004001183040.hdf
MOD04_L2.A2003364.0250.004.2004003030204.hdf
MOD04_L2.A2003364.0255.004.2004003030444.hdf
As you can see, Terra overpassed near Korean peninsula sometimes
once, sometimes twice, sometimes three times a day in 2003. In
addition, I found some missing days, but I don't know why. Anyway, the
number of *.hdf files used for this simulation was 702. If you have
something not clear in my data explanation, please let me know. Then I
will explain in Korean!! (Just kidding! ^.^).
2) What I am trying to obtain from MOD04 are aerosole optical
thickness at three different wavelength (470, 550, 660 nm) for one
year 2003. That's all I need at this point. To do this, I am making
image files for every *.hdf files, and then getting these AOT data
from appr. 70 points in those images.
* If you can give me your routine, it will greatly helpful for me to
get out of this SWAMP!
Thanks, again!!!
Harry
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| Re: Fill value problem in MODIS Processing... [message #54547 is a reply to message #54545] |
Tue, 26 June 2007 18:02  |
MarioIncandenza
Messages: 231
Registered: February 2005
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Senior Member |
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> I am currently retrieving aerosole optical thickness from MODIS04
> Aerosole product of 2003 (Level 2, collection 4, and bands of 470,
> 550, and 660 nm).
>
> There are 702 *.hdf files in 2003 and I processed these in a batch
> mode. After I ran IDL/ENVI with these data and opened the output
> file, I found about 550 of 702 lines were processed into fill value
> (-9999.99), 120 lines were N/I ("not included in the swath"). Only 30
> lines were reasonable values.
Hi Harry,
I have done a lot with MOD04_L2 files in IDL, and maybe I can help. I
have some questions:
1) MOD04 Level 2, like all MODIS L2 products, is chopped into 5-minute
granules, 288 per day. Thus 720 files is not quite 3 days of data. How
are your 720 files selected?
2) What is your processing doing that it returns one value from each
granule? The most obvious guess is that it is looking for a specific
XY location in each granule. If so, your 4% rate of return might not
be unreasonable, again depending on how the 720 files you are picking
through were selected.
I have a routine for X|Y|T extraction of data from MOD04 files. If you
have some proficiency with IDL, it can probably be adapted to your
purposes, if you are interested.
Escape the common block!
--Edward H.
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| Re: Fill value problem in MODIS Processing... [message #54554 is a reply to message #54547] |
Tue, 26 June 2007 13:24 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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DirtyHarry writes:
> Three weeks have passed since I faced this problem. I thought I could
> solve this problem by myself at first. I checked the source codes ->
> there was no problem. IDL/ENVI has been running perfectly...
> Therefore, I thought this problems was just nothing, but I got stuck
> for over 20 days... I believe it is time to listen to your
> suggestions.
>
> Is there anyone who experienced similar problem like this? Please give
> me any comments or suggestions.
If the program ran perfectly, then I think you can
assume the results are valid. It sounds as though
you don't think the results are valid. In that case,
I think I would start by re-evaluating my assumption
that a program that runs without errors runs "perfectly". :-)
Cheers,
David
"When you have eliminated all which is impossible, then whatever
remains, however improbable, must be the truth." -- Sherlock Holmes
--
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: Fill value problem in MODIS Processing... [message #54681 is a reply to message #54544] |
Wed, 27 June 2007 10:22 |
James Kuyper
Messages: 425
Registered: March 2000
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Senior Member |
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I should have mentioned this in my earlier message, but I didn't think
about it:
DirtyHarry wrote:
> I am gathering various MODIS products overpassed near Korean peninsula
> in 2003. the overpassing times of *.hdf files for this simulation are
> as follows.
...
> MOD04_L2.A2003004.0200.004.2003007020309.hdf
> MOD04_L2.A2003004.0205.004.2003007020344.hdf
> MOD04_L2.A2003004.0340.004.2003007023517.hdf
You must have used a large search region; the 03:40 file doesn't
really cover Korea, though it comes close: <http://
ladsweb.nascom.nasa.gov/browse_images/high.html?fileID=45787 585 >.
...
> As you can see, Terra overpassed near Korean peninsula sometimes
> once, sometimes twice, sometimes three times a day in 2003. In
> addition, ...
Korea is far enough north that there will occasionally be two
different orbits in which Terra MODIS day-mode data is available.
Therefore, if the break between 5-minute granules in each orbit
happens to occur while flying sufficiently near Korea, you could get
as many as four granules of data in one day.
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