Thread: FDSN StationXML schema proposal for Working Group II

Dear WG-II members,

Please find a proposal for a unified FDSN StationXML schema developed by
SCEDC/Caltech, GEOFON/GFZ, NCEDC/Berkeley and IRIS DMC, contributed by Chad.
Please have a careful look at the proposal and the attached documents
and provide feedback if needed. I strongly support this proposal.

Best regards
Reinoud

________________________________________________________________________


The purpose of this schema is to define an XML representation of the most important
and commonly used structures of SEED 2.4 metadata.

The goal is to allow mapping between SEED 2.4 dataless SEED volumes and this
schema with as little transformation or loss of information as possible while at the
same time simplifying station metadata representation when possible and adding
important details that have been "missing" from SEED. When definitions and usage
are under-defined the SEED manual should be referred to for clarification.

Another goal is to create a base schema that can be extended to represent similar data
types. We anticipate data center or project specific extensions will be created in the future
using the base schema.

We propose that these schema documents and other relevant documentation be publicly
available from the FDSN website, e.g. http://www.fdsn.org/xml/station/fdsn-station-VER.xsd

Three files are attached:

fdsn-station-0.9.xsd -- the base FDSN StationXML schema

fdsn-station+availability-0.9.xsd -- an extension of the base schema that includes time series data availability structures

Variations-FDSNSXML-SEED.txt -- an overview of major variations between SEED 2.4 and FDSN StationXML

This work is based on the existing StationXML schema developed at Caltech, in production use at the IRIS DMC and possibly other data centers. Many lessons have been learned from this early work and usage and have been incorporated into FDSN StationXML.








2012/11/03
An outline of the variations between FDSN-StationXML and SEED 2.4.

This should not be considered complete but highlights the major differences.


Features and content supported by SEED and not in FDSN-StationXML:

* Dictionary and lookup reference blockettes, there are no such concepts
in FDSN-StationXML.

* Data record blockettes, 100 and higher. FDSN-StationXML does not include
anything that would be included in miniSEED.

* Event and time span indexing blockettes. No event parameters and no
indexing relating to data records in files are contained in
FDSN-StationXML.

* Comment code keys, class code and units of comment level (blockette 31
referenced by 51 and 59). FDSN-StationXML contains comments but does not
retain these rather esoteric features.

* Generic Response Blockette 56, a simple response defined by a list of
corner frequencies and corner slopes, documented as not acceptable on their
own and should be combined with other response blockettes. This blockette
is not used by any metadata at the IRIS DMC, likely it is not widely used
or ever used at all.


Features and content supported by FDSN StationXML and not in SEED:

* Instead of the instrument identifier field of blockette 52,
FDSN-StationXML has structures at the Channel level for describing a
Sensor, Preamplifier and Datalogger with many details for each component
such as manufacturer, vendor, model, serial number, etc.

* Uncertainties for latitude, longitude, elevation, depth, azimuth, dip
and frequency.

* Comments are allowed at the Network level, in addition to the Station and
Channel levels.

* Optionally specify a sampling rate as a ratio in addition to a required
value in samples per second.

* Name and description fields for each response filter type, similar to the
name field for blockette 61 but broadened to all response structures.

* Station and Channel entries may contain an ExternalResource element to
indicate a URL to an external report or dataless or other relevant
documentation.

* Station and Channel entries can contain CreationDate and TerminationDate
attributes. These are independent of the start and end dates that define
the epoch.

* A Station entry can include one or many Equipment elements to list the
equipment common to all channels at a station.

* A Station entry can contain a Site element that includes: name,
description, town, county, region, country.

* A Station entry can include Vault and Geology descriptions.

* A Station entry can include one or many Operators. Each Operator
designation can include an agency name, a web site and contact details.

* A Contact element, used for Operators or comment Authors, can contain
name, agency, email and phone number.

* A Comment can include an Author designation.

* An alternateCode and historicalCode may be designated in addition to the
"code" for a Network, Station or Channel.

* A generic description string is supported for Network, Station and Channel
elements.

* The storage format can be denoted for Channels as a simple string
(e.g. SEED, V0, etc.)

* The restriction status (open, closed or partial) can be denoted for a
Network, Station and Channel levels.

* A resource identifier can be associated with Equipment and response filter
entries. This can be used to identify equipment in an inventory system or
entries in a catalog of response filters.

* Using a schema extension, the time series data availability can be
described for at the Network, Station and Channel levels. Availability
can be described as either extents or a subset of spans.