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20000623: NLDN data

Dave,

I've had some questions from Bob Holzworth at U. Washington regarding
the NLDN data.

He is primarily concerned with the nanosecond field which appears to
be rounded to the nearest 1/10s. I've also noticed that the 
CHI2, ECC, and ANG fields appear to always be 0 now. I think
they were non-zero at some point in history. 

Is there any information you can provide regarding the processing
of the data for the IDD?

Thanks,

Steve Chiswell
Unidata User Support





------- Forwarded Message

>To: Unidata Support <address@hidden>
>cc: Bob Holzworth <address@hidden>
>From: Robert Holzworth <address@hidden>
>Subject: Re: your mail
>Organization: UCAR/Unidata
>Keywords: 200006222212.e5MMCUT04849

Dear Steve Chiswell,
Thanks for the quick reply.  I have bought "stroke level
data" from Geomet Data in the past, and so I know
they store the data at least to the millisecond.  It
is interesting that they dont give it that way to you.
Sincerely,
Bob Holzworth
************************************************
Prof. Robert H. Holzworth
Graduate Program Advisor in Geophysics
University of Washington
Room 202 ATG Building
GEOPHYSICS 
Box 351650                   
Seattle, WA 98195-1650, USA 
************************************************
address@hidden 
http://www.geophys.washington.edu/People/Faculty/bobholz/
************************************************
206 685 7410 (office & voice mail)
206 685 3815 (fax)
************************************************


On Thu, 22 Jun 2000, Unidata Support wrote:

> Date: Thu, 22 Jun 2000 15:41:04 -0600
> From: Unidata Support <address@hidden>
> To: Robert Holzworth <address@hidden>
> Cc: address@hidden, address@hidden
> 
> 
> Robert,
> 
> The nldn files on the IDD transmit a field for "nanoseconds", which
> is used to create the milliseconds field that DCNLDN is storing.
> Looking at the data that is being transmitted, the nanoseconds value
> is always appearing as an even tenth of a second multiple, eg:
> 
> sec 961704003 nsec 300000000
> 
> Thus, converting the nsec value to 300 milliseconds is not losing any
> presicion in the decoding at your end. Rather, it is already being
> coded as a number with 1/10s resolution when the data file is
> created by the provider.
> 
> We will see if the providers of our NLDN data stream can give us more
> information on how the data is being processed to create the IDD
> datastream products and if the data values are being truncated.
> 
> Steve Chiswell
> Unidata User Support
> 
> 
> 
> 
> 
> 
> >From: Robert Holzworth <address@hidden>
> >Organization: UCAR/Unidata
> >Keywords: 200006221835.e5MIZXT27254
> 
> >Re: NLDN time resolution in data to UW
> >Dear Unidata,
> >I am a professor at the Univ. of Washington and Harry Edmon
> >(Atmospheric Sciences Department) suggested you may be able 
> >to answer my question.  
> >We get NLDN from you on a regular basis, but it seems to have time
> >resolution only to the 1/10 of a second level (0.1s), right?
> >
> >How can we get millisecond resolution?  The data files you
> >send have the time with space for the digits to the
> >millisecond, but the 10ms and 1ms digits are always zero:
> >time: 23.100  instead of 23.132 for an event at 132 ms after
> >the 23rd second.
> >
> >I realize this will make our data set expand somewhat because
> >multiplicity will then always be 1, I guess.  However, for
> >experiments I am doing this month and next we will need
> >stroke-level NLDN data.  
> >
> >Is it possible to increase the time resolution for us?  If
> >this is a problem for the routine processing, would it be
> >possible to get stroke level data after the fact for
> >particular subsets of the data?  
> >
> >Thanks,
> >Bob Holzworth
> >************************************************
> >Prof. Robert H. Holzworth
> >Graduate Program Advisor in Geophysics
> >University of Washington
> >Room 202 ATG Building
> >GEOPHYSICS 
> >Box 351650                   
> >Seattle, WA 98195-1650, USA 
> >************************************************
> >address@hidden 
> >http://www.geophys.washington.edu/People/Faculty/bobholz/
> >************************************************
> >206 685 7410 (office & voice mail)
> >206 685 3815 (fax)
> >************************************************
> >
> 
> 


------- End of Forwarded Message