Blacknest BDS Meta Data Definitions
Date |
2009-02-18 |
Version |
0.5 |
Note that this is a "work in progress" document and is being continually updated.
Introduction
This document describes all the Meta data used in the BDS system.
There are two groups of Meta Data used in the BDS system.
- Data File MetaData: This meta data provides information on the
raw data stored in the data files. This includes time periods, the
station and channel the data is from, the sampling rate and sample
format.
- Channel MetaData: This meta data provides information on the
source of the data. This includes the physical location of the sensors,
the type of sensors and sensor calibration information.
Data File MetaData
In order to simplify and generalise data file metadata information, the Bds Data File
API provides meta data information in the form of a set of named values
implemented as a String dictionary. This allows arbitrary information
to be stored. In order to generalise and simplify usage a set of
standard parameters are defined. These are:
Item Name |
Description |
startTime |
The start time of the following data. |
endTime |
The end time if a file format (not in streamed data) |
array |
The Array the data is from if only from a single array |
description |
General description |
channels.number |
The number of channels |
channels.synchronous |
A boolean defining if the channels are synchronously sampled |
channel1.startTime |
The start time |
channel1.endTime |
The end time |
channel1.network |
The network the data is from |
channel1.station |
The station the data is from |
channel1.channel |
The channels identifier name |
channel1.source |
The data source, "Master" is the normal. |
channel1.type |
The channels type (BHZ etc) |
channel1.auxId |
The auxillary or location ID. |
channel1.numSamples |
The total number of samples if known, 0 otherwise |
channel1.sampleRate |
The channels sample rate |
channel1.sampleFormat |
The sample format Int16, Int32, Float32 etc |
channel1.format |
The file format. BDS, BDRS, GCF etc |
channel1.formatOriginal |
The original data format this file was created from |
Networks
The network is the sesmic organisations name. This is
limied to two characters in SEED files. A list of valid network names
is given in the following list: http://www.iris.washington.edu/stations/networks.txt
Station Names
The station names used in the BDS system should match the IDC standards: USG85 and IMS01. This states:
Seismic station and site names shall be registered with the International Seismic Centre (ISC) or the
National Earthquake Information Center (NEIC) of the U.S. Geological Survey. Seismic station and site
names shall conform to standards given in [USG85]. For example, station names shall be three to five
characters in length, and therefore the station field will never be completely filled. No counterpart
registry exists for hydroacoustic and infrasonic station or site names, but station and site name formats
shall conform to IMS station naming conventions [IMS01].
In addition to the standard names there are some specific Blacknest names to handle particular data channels. These are:
Channel Types
The channel types and channel auxId used in the BDS system should match the IDC standards FDSN) [IRI93]
and IMS01 for the Channel Name. Note that the BDS uses a channel name
that is the channel type and channel auxId combined with a "_"
character. If there is no auxId, the "_" character is omitted.
The channel name is the three-character string that labels the bandwidth, gain, and orientation of the
sensor. Channel names for seismic
stations shall conform to the standards of the Federation of Digital
Seismograph Networks (FDSN) [IRI93]. Channel names that are not defined
by the FDSN shall conform to IMS channel naming conventions
[IMS01]. The location field is provided in anticipation of the
need to distinguish between two or more sensors at one site with the
same channel name. Although a location identifier is included in the
SEED format [IRI93], no convention has been defined for location naming.