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FDSN / StationXML

The FDSN StationXML schema and related documents
https://docs.fdsn.org/projects/stationxml/
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add Unity filter type to hold units #22

Open crotwell opened 5 years ago

crotwell commented 5 years ago

There are many cases, preamp gain-only stages as well as many SOH channels, where there is no known frequency dependency to the response. Often these are represented by a Stage with only a StageGain, but this means that there is no place to put the input and output units, and the client is left to guess them based on the preceding and following stages. And this is a problem if there is only one stage.

Adding a Unity filter that simply extended BaseFilterType to hold the units would make working with these types of stages easier and clearer as well as making it easier to force units to be specified within the schema.

Related to #20

metempleton commented 4 years ago

Note that SOH channels use a pole/zero stage with no poles or zeros to document units.