| Re: IDL code to read MSU and HIRS in Level1b [message #40630 is a reply to message #40572] |
Fri, 20 August 2004 07:44  |
Yamout
Messages: 8
Registered: August 2004
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Junior Member |
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Dear Makr,
thank you for your response.
I have not ever touched TOVS data after 1991. It is not my problem to
read those data. My problem is to read the TOVS data before 1995.
I have ordered and downloaded one of the TOVS sensors called MSU and
tired to read this data as is described in POD User's Guide. After many
weeks of errors, I discovered that those data are in a "little bit"
different format. But the problem now is that the differences are not
the same as the notes from the automatic help mail from SAA. The
following is the last so called help which could get from the robot there:
---------------------------------
In response to your SAA Help Desk inquiry
E-Mail : Dear Hossein Yamout,
The only difference between the data from before and after January
1, 1995 is the record length. For data from prior to 1995, there were
additional spare bytes at the end of each data record, effectively
increasing the overall record length. In particular, for the line item
you referenced, L5409101, which was for MSU data, you will want to look
at section 4.3 of the POD Guide
http://www2.ncdc.noaa.gov/docs/podug/html/c4/sec4-3.htm
If you look at table 4.3.2.1-1. titled Format of MSU data, you will
see that pre-1995 data had spare bytes in byte locations 401 to 440
while the data starting in 1995 had spare bytes in byte locations 401 to
437. Otherwise, the formats are identical. If you are interested in the
other TOVS data types, they too had a record length change starting in
1995. The appropriate section of the POD Guide spells out the record
length change for these data types as well. For SSU data, see
http://www2.ncdc.noaa.gov/docs/podug/html/c4/sec4-2.htm
and for HIRS data see
http://www2.ncdc.noaa.gov/docs/podug/html/c4/sec4-1.htm
I hope this clarifies this matter for you.
Sincerely,
CLASS Help Desk
------------------------------------
The robot in SAA help desk have not realized that there is not only one
different between the post and past level1b formats of TOVS data, but
there are many others.
By the way, after so many weeks of mailing and now posting, I have
received no one (among them many meteorologists in NOAA) which reply me
with the word "sorry" somewhere in their mail. Apparently there are not
so many people (even high experts in NOAA) who have ever used these
data. The next question which would one make is, why they operate and
produce so many satellite data which no one can / have used.
If you would like I can make a long list of meteorologists and satellite
experts which I have sent a mail and have got "sorry" answer or no
answer at all.
I the field of remote sensing I have been met many times some statements
in which one claims that has done this or that but nobody can follow how
it has been done or if it has ever been done as it is claimed. If it is
calibration or correction of a satellite image or just some remotely
sensed maps or other earth surface products.
So I suppose would enough for the time being. If you are still
interested in this matter, just let me know.
Yours
Hossein
~~~~~~~
Mark Hadfield wrote:
> Yamout wrote:
>
>> Dear Mark,
>>
>> thank you for your reply. As I said, I have ENVI with full version of
>> IDL unfortunately in PC (windows) platform. As you have written there
>> are some differences between the before and after 1995 formats. I have
>> asked SAA people and they can only send me such "helps" which I knew
>> already.
>
>
> So are you saying that you *can* read the post-1995 format? If so, how?
> Is there any possibility of your modifying the reader for the post-1995
> file so that it will cope with the difference in record length?
>
> Please be patient if the answers to these questions seem obvious to you,
> but I don't know much about ENVI. Please realise when you post questions
> to a news group that you need to give the readers enough information for
> them to help you.
>
> ---
> Mark Hadfield "Ka puwaha te tai nei, Hoea tatou"
> m.hadfield@niwa.co.nz
> National Institute for Water and Atmospheric Research (NIWA)
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