[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

20000410: Converting POES Level 1b to McIDAS Format

This archive contains answers to questions sent to Unidata support through mid-2025. Note that the archive is no longer being updated. We provide the archive for reference; many of the answers presented here remain technically correct, even if somewhat outdated. For the most up-to-date information on the use of NSF Unidata software and data services, please consult the Software Documentation first.

  • Subject: 20000410: Converting POES Level 1b to McIDAS Format
  • Date: Tue, 11 Apr 2000 19:22:04 -0600
>From: Salottolo Greg <address@hidden>
>To: "'McIDAS Users Mail Group'" <address@hidden>
>Date: Mon, 10 Apr 2000 08:54:05 -0400
>Organization: National Transportation Safety Board
>Keywords: 200004101258.GAA07884 McIDAS convert AVHRR Level 1B AREA

Good Morning:

Any thoughts on converting POES Level 1b data obtained from the Satellite
Active Archive (SAA) to McIDAS Format? I have tried using the XRD Command
CONVERT_LEV1B but it does not seem to work. I have tried 10 bits/pixel, 8
bits/pixel, and 16 bits per pixel. I was told that the 8 and 16 bits per
pixel data is unpacked. It is my understanding that the CONVERT program only
works with NOAA15 unpacked data.

Any help would be appreciated.

Thanks..

Greg 

Gregory D. Salottolo
National Resource Specialist, Meteorology

National Transportation Safety Board
Office of Aviation Safety (AS-30)
490 L'Enfant Plaza SW
Washington D.C. 20594

202.314.6338 Work
202.314.6339 Fax
e-mail: address@hidden
Pager: 877.342.3320


From: John Benson <address@hidden>
Subject: Re: Converting POES Level 1b to McIDAS Format
To: address@hidden
Date: Mon, 10 Apr 2000 10:59:25 -0500 (CDT)

      Here's a quick-check.

The program knows that the 4th byte of the header record is an ascii
blank (hex 20).  It checks the fourth byte of the file.  If it isn't
right, it assumes the first 512 bytes of the file are an SAA preamble.
So it tabs 512 bytes into the file and tries again.  If it still can't
find a blank, it gives up.

So take a look at your raw data.  The first four bytes should probably
be N S S <blank>.  Either starting at the very beginning of the file,
or starting at byte 512.  If they aren't, we don't know what you've
got.

The next thing to check is the record length.  If it's the right
format, each record (including the header) should all be the same
length, which is 22,528 bytes.

    --address@hidden


From: John Benson <address@hidden>
Subject: Re: Converting POES Level 1b to McIDAS Format
To: address@hidden
Date: Mon, 10 Apr 2000 13:30:03 -0500 (CDT)


I find a proper header record at data + 512 bytes, which indicates that
the data is GAC.  That means the record length should be 5632 bytes.

But when I look at byte 6144 (5632 + 512) I do not see reasonable
data.  The date is somewhere in the sixth century C.E.

So I'm not sure exactly what you've got.

    --address@hidden

11-APR-2000 16:01 deew

Told Greg that there is a command in XRD, CONVERT_LEV1B, that
works on NOAA-15 level 1B data.

Greg was unable to get it to work.

Contacted Greg to get the specifics of his request. We did some testing
here and found that you MUST REQUEST 16 bit data and all bands. If you
request 8 or 10 bit and fewer bands the program in XRD will not make an
usable area.