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wiki:pkfilter.designspecs.txt
Last modified 18 months ago Last modified on 03/25/12 13:57:18

    Design Requirements for a Pick Filter

    1. The purpose of the pick filter is to reduce the number of "duplicate" picks
       from a given "station". For the pick filter, all components which have
       matching station code and network code are considered to be the from the
       same "station". The rules for what are considered "duplicate" picks are
       given below.

    2. For each "station", the pick filter will maintain a history list of picks
       that have been allowed through the filter. The size of these lists will be
       limited by a configurable number (count) of picks.

       LDD: Added the "PickHistory" command to specify the number (count) of
       picks that will be maintained in the list for each "station".
       Only picks which pass the filter rules are added to the list. Once
       the list is full, old picks are removed in a simple first-in, first
       overwritten manner.

    3. The pick filter can optionally be configured to pass picks from only
       certain component codes.

       LDD: Added "AllowComponent" command. If no "AllowComponent" command is
       used, ALL components will be allowed to pass. If one or more "AllowComponent"
       commands are used, the pick filter will only pass picks from the listed
       components.

    4. The following rules may be used to determine if a pick is allowed through
       the filter. Any pick that fails these rules is considered a "duplicate" and
       is rejected by the filter.

       A new pick is considered to "match" a pick in the history list if the two
       pick times are within "pick tolerance" of each other. That is, a new pick
       within "pick tolerance" before or after a listed pick is considered to
       match the listed pick.

       LDD: Set with original "PickTolerance" command.

       a. A pick that is more than "pick tolerance" newer than the most recent
          listed pick is always passed by the filter.

       b. "Allow higher quality matches": A pick that "matches" a listed pick and
          has a higher quality than that matching pick is optionally passed by the
          filter.

          LDD: Set with original "DuplicateOnQuality" and "QualDiffAllowed" commands.

       c. "Allow older": A pick that is more than "pick tolerance" older than the
          older listed pick is optionally passed by the filter.

          LDD: Added two new commands to control this feature.
          "OlderPickAllowed" has 3 possible values:
            0=pass no non-duplicate picks older than the youngest passed
              pick for this station.
            1=pass older picks, but set a limit on how old they can be.
            2=pass all non-duplicate picks older than the youngest pick
              for this station.
          "OlderPickLimit" is used only if OlderPickAllowed=1. If a
           non-duplicate pick is older than they youngest-passed pick by
           more than OlderPickLimit seconds, the pick will be rejected.

           I included the "OlderPickLimit" option because I noticed in CI data,
           that some channels at a station can arrive many minutes later than
           another channel at the same station.  I assume that this is due to
           recovery on a bad telemetry link.  If we want to keep the pick history
           relatively short and still let older picks thru, we need to set a time
           limit on the oldest picks we'll accept. Otherwise we could still end up
           with lots of duplicates in the system.  And if new picks exist, the older
           ones won't really help binder at all.

    5. Coda messages can also be filtered by the pick filter. The options should
       include "allow all", "allow none", and "allow matching". Codas are
       considered to match picks for a given "station" if the pick and coda have
       the same serial number, installation and module IDs. The Earthworm picker
       assigns serial numbers to picks and codas; the installation and module IDs
       are part of the "logo" assigned to all Earthworm messages.

       LDD: Added "CodaFilter" command for this feature.
            It has 3 possible values:
            0=allow no codas
            1=allow matching codas
            2=allow all codas

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