Configuring the LDM to Run the Decoders

Even though they can run "by hand", LDM-MCIDAS decoders are typically run as actions of the LDM's pqact utility.

Five decoders, pnga2area and pngg2gini, nldn2md, proftomd, and zlibg2gini, are used to decode PNG-compressed MCIDAS (Unidata-Wisconsin) and FNEXRAD imagery, NLDN lightning data from SUNY Albany, FSL2 Wind Profiler data, and Zlib-compressed NOAAPORT GINI imagery, respectively. Decoded imagery is usable in all Unidata supported application packages (i.e., GEMPAK, McIDAS, and IDV); non-imagery products are decoded into McIDAS-compatible formats.

Additional decoders included in the LDM-McIDAS distribution do not work on current datastream products, but continue to be included for sites that have archives of Unidata-Wisconsin products included in the IDD before July of 1999.

cdftomd, nids2area, gunrv2, lwfile, lwtmd2, and lwtoa3 decode FSL Wind Profiler, WSI NIDS, and pre-2000 Unidata-Wisconsin datastream products into McIDAS format data files. gunrv2, lwfile, and lwtmd2's use was obsoleted by the removal of GRID, TEXT, and MD files from the Unidata-Wisconsin datastream on July 1, 1999. lwtoa3's use was obsoleted by the switch to use of PNG-compressed images in the Unidata-Wisconsin datastream in August of 2000. cdftomd's use was obsoleted by the introduction of proftomd. nids2area can still be run to create McIDAS AREA files from uncompressed WSI-format NIDS products, but it is recommended that sites receiving WSI NIDS or IDD NEXRAD Level III products use the McIDAS-X 7.8+ NEXRAD LEVEL III ADDE server to access these data files instead.

After the LDM-McIDAS decoders are installed, you need to configure your LDM pqact.conf file to run the LDM-McIDAS decoders that you want to use. Annotated example pqact.conf entries for the decoders can be found in LDM Pattern-Action File for LDM-MCIDAS Decoders. A stripped down version of this file suitable for inclusion in the LDM's pqact.conf file is available in ldm-mcidas-pqact.conf.all. To transfer this to your machine, hold down the Shift key while pressing mouse button 1 over the link.

The ldm-mcidas-pqact.conf.all entries were written assuming that you want to decode data into the following directories:

If you are using these same directory structures, configuring your LDM pqact.conf file should be as simple as copying the ldm-mcidas-pqact.conf.all entries you want to use into ~ldm/etc/pqact.conf, verifying the integrity of pqact.conf, and then sending a HUP signal to your LDM's pqact process (this assumes you are running reasonably current versions of the LDM; if you are not, please contact Unidata User Support for help).

Type the following:

      cd ~ldm/etc
    

Edit pqact.conf and add entries from ldm-mcidas-pqact.conf.all. Then type:

      ldmadmin pqactcheck
    

Correct any errors in pqact.conf, and then type:

      ldmadmin pqactHUP
    

NOTES:

• LDM-MCIDAS decoders are designed to work on one product at a time. It is important, therefore, to include the -close option on pqact lines for each LDM-MCIDAS decoder.
• The PNG AREA file encoder (compressor), area2png and PNG compressed AREA file decoder (uncompressor), pnga2area require information from the McIDAS satellite annotation, SATANNOT, and satellite band description, SATBAND, files. Copies of these files should be placed in a directory whose location will be used in the LDM's pattern-action file, pqact.conf. We recommend the ~ldm/etc directory for this purpose.

  The information needed by the decoders is as follows:

  Encoder/Decoder	McIDAS Information Files
  area2png	SATANNOT, SATBAND
  pnga2area	SATANNOT, SATBAND
  pngg2gini	none

• Several LDM-MCIDAS decoders require information contained in the McIDAS schema file, SCHEMA. SCHEMA is distributed with both LDM-McIDAS and McIDAS-X.

  The information needed by the decoders is as follows:

  Decoder	Schema	Schema Template File(s)
  cdftomd	WPRO	DCWPRO
  nldn2md	NLDN	DCNLDN
  proftomd	WPRO, WPR6	DCWPRO, DCWPR6

  In McIDAS, schema are registered in SCHEMA using the SCHE command and an appropriate schema template file. The McIDAS-X invocation examples will register the NLDN (NLDN), FSL hourly summary profiler (WRPO), and FSL 6-minute profiler schema (WPR6) in SCHEMA:

            SCHE DCNLDN
            SCHE DCWPRO
            SCHE DCWPR6
          

  A copy of SCHEMA with appropriate entries for the output file types needs to be placed in the directory in which the LDM-McIDAS decoders create their output data files.

  SCHEMA must be readable AND writable by the user running the LDM and LDM-MCIDAS decoders.

• LDM-MCIDAS image decoders can use McIDAS file routing concepts. To enable the use of McIDAS file routing, you MUST use a routing table, ROUTE.SYS, that has been created by McIDAS-X, and it MUST be copied to the directory into which the decoders create output data files. A copy of ROUTE.SYS configured to support decoding of imagery conveyed in the IDD is included both in Unidata McIDAS-X and in LDM-McIDAS.

  ROUTE.SYS must be readable AND writable by the user running the LDM and LDM-MCIDAS decoders.

• LDM-MCIDAS decoders can also update the McIDAS System Key Table, SYSKEY.TAB, with information about data received. In order to have SYSKEY.TAB updated automatically upon receipt of new products, it MUST exist in the directory in which decoders create output data files. A copy of SYSKEY.TAB is included both in Unidata McIDAS-X and in LDM-McIDAS.

  SYSKEY.TAB must be readable and writable by the user running the LDM and LDM-MCIDAS decoders.

• Since it is strongly recommended to not configure the ldm account with knowledge of McIDAS processes, there is no direct way to have LDM-MCIDAS decoders execute McIDAS ROUTE PostProcess BATCH files. Unidata has, however, developed a procedure that allows sites running the LDM and McIDAS-X to execute ROUTE PostProcess BATCH commands upon the receipt of data products in the Unidata-Wisconsin stream. Detailed information on setting up your system to do this is found in the README.PP file in the src/decoders subdirectory of the LDM-MCIDAS distribution.

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