Channel
Description
An OBS channel is an Instrument plus an orientation. An Instrumentation complex consists of one or several channels, each one implementing the signal processing of an instrument.
Actual channels all have string labels, which are usually channel numbers. They must specify an orientation. Default chann properties can be specified with a label default
. This is not an actual channel. These properties are common to all channels unless overridden by attributes present in specific channels. For example, if a sensor X appears under the label default
but a sensor Y appears under the label “2” then for channel 2 the selected sensor will be Y. If a preamplifier Z is specified under the label default
and no preamplifier is specified under the label “2”, then channel 2 will have preamplifier Z. All attributes can be specified under the default
label.
Configurations are defined at the instrument component level, but are selected at the channel level. A configuration selection attribute specifies a configuration for each of the three instrument components in a channel: sensor, preamplifier and datalogger. They are the attributes sensor_configuration, preamplifier_configuration and datalogger_configuration, respectively.
Python class:
Channel
YAML / JSON label:
channels
default
Particular string labels for each channel
Channels are part of the instrumentation information file.
Corresponding StationXML structure
Channel
Object Hierarchy
Superclass
None
Subclasses
None
Relationships
Implements the signal of an Instrument
Is part of an Instrumentation
Attributes
Name |
Type |
Required |
Default |
Equivalent StationXML |
Remarks |
instrument |
Y |
None |
None |
Attributes of instrument in Channel in StationXML |
|
orientation: |
Orientation |
Y |
None |
None |
|
|
List of values: X,Y,Z,1,2,3,H |
Y |
None |
None |
If orientation code is 1,2,3 or H it must include as a dictionary azimuth and dip. See example. |
|
number |
Y |
None |
Channel. Azimuth |
0.0 ≤ Azimuth < 360.0 in degrees |
|
number |
Y |
None |
Channel. Dip |
-90.0 ≤ Dip ≤ 90.0 in degrees |
location_code |
string |
Y |
None |
See LocationBase for details of how location codes are used. |
|
sensor_configuration |
string |
N |
None |
None |
For obsinfo use only. This selects one of the configurations defined in the instrument components. |
preamplifier_configuration |
string |
N |
None |
None |
For obsinfo use only. This selects one of the configurations defined in the instrument components. |
datalogger_configuration |
string |
N |
None |
None |
For obsinfo use only. This selects one of the configurations defined in the instrument components. |
Orientation codes are a FDSN standard. By convention, if the orientation code is X, Y or Z, these represent the regular coordinates in space following the right-hand rule, within five degrees of the actual directions. So X corresponds to an azimuth of 0º and a dip of 0º, Y corresponds to an azimuth of 90º and a dip of 0º, and Z corresponds to an azimuth of 0º and a dip of -90º (the positive Z direction is towards the bottom). However, if 1, 2 or 3 are specified, these represent three linearly independent directions but not necessarily coincidental with the regular coordinates, so an azimuth and a dip _must_ be specified. The same is true of the H (hydrophone) code.
JSON schema
https://www.gitlab.com/resif/obsinfo/-/tree/master/obsinfo/data/schemas/instrumentation.schema.json
https://www.gitlab.com/resif/obsinfo/-/tree/master/obsinfo/data/schemas/definitions.schema.json
Example
Channels part of instrumentation information file https://gitlab.com/resif/obsinfo/-/tree/master/obsinfo/_examples/Information_Files/instrumentation/BBOBS1_2012%2B.instrumentation.yaml
channels:
default:
datalogger: {$ref: "dataloggers/LC2000.datalogger.yaml#datalogger"}
preamplifier:
{$ref: "preamplifiers/LCHEAPO_BBOBS.preamplifier.yaml#preamplifier"}
sensor: {$ref: "sensors/NANOMETRICS_T240_SINGLESIDED.sensor.yaml#sensor"}
preamplifier_configuration: "0.225x"
"1": {orientation_code: {"2": {azimuth.deg: [90, 0]}}}
"2": {orientation_code: {"1": {azimuth.deg: [0, 0]}}}
"3":
orientation_code: "Z"
preamplifier_configuration: "1x"
"4":
orientation_code : {"H": {azimuth.deg: [0,0], dip.deg: [90,0]}}
preamplifier: {$ref: "preamplifiers/LCHEAPO_DPG.preamplifier.yaml#preamplifier"}
sensor: {$ref: "sensors/SIO_DPG.sensor.yaml#sensor"}