20050727: acars and the -b option

Neil,

The -b option to dcacars has a different meaning than the
"-b num hours before" that dcmetr etc. use to reject observations
that might arrive some -b hours before the current time.

In Dcacars, -b  is a time binning parameter which would allow you to
collect observations into a file of a certain number of minutes.
Without -b, you would get 60 acars files each hour if using the NN
template, but using -b 30, you would get 2 files (eg HH00 and HH30).

The dcacars pattern I provide does not use that -b flag, as I am using
YYYYMMDDHH_acars.gem as the file name.

If there were to be more observations in an hour than could fit into an
hourly file, then we would have to use NN, and then probably 15 minute files.
The -b flag in dcacars does not reject data. Dcacars will compare station ID
and location at a time and remove duplicates though when the data is 
retransmitted.
Dcacars bases the file name template on the data within the netcdf file, for 
each
observation. If there are multiple hours, days or observation in the acars 
file, then dcacars
will create the necessary data files based on the file template.

The LDM strftime templates can only operate on the LDM product date/time and
not on data within the NetCDF file, so would not be appropriate. 

Steve Chiswell
Unidata User Support



>From: Neil Smith <address@hidden>
>Organization: UCAR/Unidata
>Keywords: 200507280430.j6S4UCjo000346

>GEMPAK 5.8.2a
>LDM 6.0.14
>
>I'm decoding acars data with:
>
>PCWS    ^FSL\.CompressedNetCDF\.MADIS\.acars\.
>         PIPE    -close  decoders/dcgunzip decoders/dcacars -b 30
>         -e GEMTBL=/unidata/nawips/gempak/tables
>         -l /unidata/ldm/logs/dcacars.log
>         data/gempak/acars/YYYYMMDDHHNN_acars.gem
>
>and requesting with
>
>request PCWS            "^FSL\.CompressedNetCDF\.MADIS\.(acars)"
>
>Since a lot of the reports come in so 'late', I was thinking that the
>'-b 30' option would still 'bin' the late reports into the correct
>corresponding gempak file. But on re-reading the meaning of the
>-b option, I guess I shouldn't expect this -- there may be reports from
>30 hours before HHNN filed in a given .gem file. Is that correct?
>
>I would like a YYYYMMDDHHNN to only have reports for that time in
>a given gempak file. Is it possible and how is it done?
>
>(I guess I still don't understand the different effects of the 
>YYYYMMDDHHNN
>format and the (1:yy), etc. format, if indeed that is how one 'bin's 
>reports)
>
>Thanks,
>-Neil
>------------------
>Neil R. Smith                          address@hidden
>Comp.Sys.Mngr.                 (979)845-6272
>Dept. Atmospheric Sciences/Texas A&M University
>
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