Re: Now Level II NEXRAD data files are bogus??

• To: ldm-users@xxxxxxxxxxxxxxxx; poker@xxxxxxxxxxxxxxx;
• Subject: Re: Now Level II NEXRAD data files are bogus??
• From: Kevin W. Thomas [mailto:kwthomas@xxxxxxxxxxxxxxxxxx]
• Date: Thu, 13 Jun 2002 16:34:21 -0500

Just a heads up if you are using NEXRFILE (the SSEC McIDAS method of filing
this data) it stopped working at 17:30Z today.  I a sure it's all related.
I am using my LDM feed as a workaround, but the McIDAS Help Desk folks
are already on the case.



-----Original Message-----
Sent: Thursday, June 13, 2002 3:57 PM
support@xxxxxxxxxxxxxxxx


>All,
>
>Starting around 17:30 UTC, the level II files coming in over the NEXRAD
>feed are unreadable by gempak, wxp, whatever.
>
>The 1km composites are ok though.
>
>Did something bad and unexpected happen when they switched over
>to the new Linux servers?
>
>Yet another update to Gilbert's last status update:
>
>
>NOUS72 KNCF 131721
>ADMNCF
>PLEASE PASS TO MIC, HIC, ESA, SOO AND ITO:
>IN ORDER TO ALLEVIATE LATENCY IN SENDING TO THE AWIPS SBN, THE NCF
>INTENDS TO MOVE UPLINK OF THE GATEWAY (NWSTG) CHANNEL TO A NEWLY
>INSTALLED LINUX UPLINK.  THIS WILL OCCUR AT APPROXIMATELY 18Z.
>
>NCF/KJ
>
>
>Pete
>
>--
>+>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>+<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<+
>^ Pete Pokrandt                    V 1447  AOSS Bldg  1225 W Dayton St^
>^ Systems Programmer               V Madison,         WI     53706    ^
>^                                  V      poker@xxxxxxxxxxxxxxx       ^
>^ Dept of Atmos & Oceanic Sciences V (608) 262-3086 (Phone/voicemail) ^
>^ University of Wisconsin-Madison  V       262-0166 (Fax)             ^
>+<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<+>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>+

I'm receiving corrupted NEXRAD Level II files.

I have my own indexing software which works on NEXRAD data files, whether
they
are LDM, tape, or live/RIDDS.  Up until today, it has always worked fine.
Today, it core dumps on some 88D files.

Due to a design flaw in BZIP2 format, there is no way of knowing the length
of data when it is uncompressed without uncompressing it.  As a result, the
format for LDM has segments that have an encoded length in it followed by
data.  This pattern repeats until the end of the file.  This normally up to
a
5 digit number.  Today, I'm seeing 10 digit lengths at the corruption point.
Something is making a mess of the data.

        Kevin W. Thomas
        Center for Analysis and Prediction of Storms
        University of Oklahoma
        Norman, Oklahoma
        Email:  kwthomas@xxxxxx