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20000802: pnga2area pqact.conf setup question question

>From: Adam Burnett <address@hidden>
>Organization: Colgate
>Keywords: 200008021416.e72EGDT23082 ldm-mcidas pnga2area Unidata-Wisconsin


>I have a quick question about the PNG compression and the use of pnga2area.


>I downloaded the binary distribution of the new ldm-mcidas decoders, made
>the adjustment to my pqact.conf file (following the example pqact.conf file)
>to include the action:
>MCIDAS ^pnga2area Q. (..) (.*) (.*) (.*) (.*) (........) (....)        PIPE
>       /data2/ldm/ldm-mcidas7.6.4/bin/pnga2area -d /data3/mcfiles

Hmm...  You are the second person that missed specifying the '-r' flag
when specifying the '-d' flag.  I am now suspicious that the example
pqact.conf entry is wrong or unclear.  Can you tell me if you were looking
at the example in the ldm-mcidas distribution or something on the web?
Thanks in advance.

To set the story straight, the pqact entry should look like:

MCIDAS  ^pnga2area Q. (..) (.*) (.*) (.*) (.*) (........) (....)
        PIPE    -close  
        /data2/ldm/ldm-mcidas7.6.4/bin/pnga2area -d /data3/mcfiles -r \1,\2


o the white space after MCIDAS, before and after PIPE, and before /data2
  are tabs not spaces

o the '-d' and '-r' flags are used in combination with each other; they
  can not be used separately.  '-d' tells pnga2area where to put the
  decoded output data file, and the '-r' flag says to try and use the
  McIDAS routing table, ROUTE.SYS, in the generation of the name of the
  output data files.

>I then commented out my lwtoa3 action.  It is my understanding from the
>recent email notices that all imagery, including the new cloud top
>temperatures, sst, etc, will be PNG compressed.

Yes.  We are dropping the delta encoded images (that get unravelled by
lwtoa3) in favor of the PNG compressed ones.  Tests comparing the
efficiency of the two methods demonstrate that PNG is vastly superior
to the delta encoding scheme, esepcially for VISible imagery.

>I also ran the CIMSS.BAT file to update my ROUTE table.


>After my changes, I received no imagery.

You probably mean that you decoded no imagery.

>I then reinstated the lwtoa3
>(knowing the old style imagery were still being sent) and things began to
>work again (except for no new cloud top temp, sst, etc.).  Bottom line - I'm
>not getting any png2area action.
>Have I missed something?

Yes, the -'r' flag as I indicate above.

After you make your modifications to pqact.conf, you should always test
them before sending a HUP signal to pqact.  If you are running a
relatively current version of the LDM, you can make the test by

ldmadmin pqactcheck

If you are running an old version of the LDM you should consider
upgrading, but you can still check the validity of the file by running
pqact by hand.  The test would be:

pqact -vl - -q /dev/null pqact.conf

You will get an error about not being able to open the product queue,
but that will be after the integrity of pqact.conf is checked.

Once you are decoding the imagery that is being sent in PNG compressed
format (i.e., once your pnga2area stuff is working), you would do well
to modify your ldmd.conf file to change the request line for MCIDAS
data.  The reworked line will look something like:

request MCIDAS "^pnga2area Q[01]" upstream_feed_site_name

Note, however, that your existing request for data might be something
like 'request UNIDATA' which includes MCIDAS.  In this case, you would
do well to split your request into two:  one for MCIDAS specifically,
and the other for all of the other feeds that you want.  This might
look like:

request DDPLUS|IDS|HRS|FSL2 ".*" upstream_feed_site_name
request MCIDAS "^pnga2area Q[01]" upstream_feed_site_name

>Thanks - Adam

Please let me know if the pqact.conf entry above does or doesn't work
for you.


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