Channel codes¶
Band, source and subsource codes¶
A channel is composed of a sequence of three codes that each describe an aspect of the instrumentation and its digitization as follows:
Band: Indicates the general sampling rate and response band of the data source. May be empty for non-time series data.
Source: Identifies an instrument or other general data source. Cannot be empty.
Subsource: Identifies a sub-category within the source, often the orientation, relative positon, or sensor type. The meaning of subsource codes are specific to the containing source. May be empty.
A channel is the combination of these three codes separated by “_”
(ASCII 95) in the following pattern: Band_Source_Subsource, which
forms the end of a source identifier.
For usage of Band codes A and O (both deprecated), the source and subsource codes may be defined by the generator. In these cases, the source and subsource codes should not exceed three characters each in length. In all other cases, source and subsource codes defined in this specification must be used.
Two sequences are reserved for special channels, both deprecated: L_O_G for the console log and S_O_H for general state of health.
Note
All channels with single-character Band, Source, and
Subsource codes are equivalent to SEED 2.4 channel designations
and vice versa.
Band Code¶
The band code specifies the general sampling rate and the approximate response band of the instrument (when applicable to the data source).
Band code |
Band type |
Sample rate (samples per sec) |
Lower bound (sec) |
|---|---|---|---|
J |
… |
> 5000 |
|
F |
… |
>= 1000 to < 5000 |
>= 10 sec |
G |
… |
>= 1000 to < 5000 |
< 10 sec |
D |
… |
>= 250 to < 1000 |
< 10 sec |
C |
… |
>= 250 to < 1000 |
>= 10 sec |
E |
Extremely Short Period |
>= 80 to < 250 |
< 10 sec |
S |
Short Period |
>= 10 to < 80 |
< 10 sec |
H |
High Broadband |
>= 80 to < 250 |
>= 10 sec |
B |
Broadband |
>= 10 to < 80 |
>= 10 sec |
M |
Mid Period |
> 1 to < 10 |
|
L |
Long Period |
~ 1 |
|
V |
Very Long Period |
>= 0.1 to < 1 |
|
U |
Ultra Long Period |
>= 0.01 to < 0.1 |
|
W |
Ultra-ultra Long Period |
>= 0.001 to < 0.01 |
|
R |
Extremely Long Period |
>= 0.0001 to < 0.001 |
|
P |
On order of 0.1 to 1 day |
>= 0.00001 to < 0.0001 |
|
T |
On order of 1 to 10 days |
>= 0.000001 to < 0.00001 |
|
Q |
Greater than 10 days |
< 0.000001 |
|
I |
Irregularly sampled |
irregular |
|
A |
Administrative |
variable, DEPRECATED |
|
O |
Opaque |
variable, DEPRECATED |
Source and Subsource Codes¶
The source code specifies the family to which the sensor belongs or otherwise a general data source. In essence, this identifies what is being measured or simulated. Each of these source types are detailed in this section.
The subsource code provides a way to indicate the directionality of the sensor measurement (orientation), the relative location of the sensor or the sensor type. Subsource codes are source-specific.
Geographic orientation subsource codes
Traditional orientation values of North-Source (N), East-West (E), and Vertical (Z) should only be used when within 5 degress of true directions. Do not use N or E designations if the orientation of horizontal components is known to deviate more than 5 degrees from true North/East.
For orthogonal components that are in nontraditional orientations, if the orientation of the horizontal components is known to deviate more than 5 degrees from true North and East, the respective channels should be named 1, 2 instead of N, E (N->1, E->2).
For sources that record data in a direction typically aligned with geographical coordinate systems, the subsource identifier should follow these conventions (where appropriate):
Subsource codes
Description
N, E, Z
Traditional orientations of North (N), East (E), and Up (Z)
When within 5 degrees of true directions
1, 2, Z
Orthogonal components, nontraditional horizontals
1, 2, 3
Orthogonal components, nontraditional orientations
T, R
For rotated components or beams (Transverse, Radial)
A, B, C
Triaxial (Along the edges of a cube turned up on a corner)
U, V, W
Optional components, also used for raw triaxial output
Seismometer¶
Measures displacement/velocity/acceleration along a line defined by the the dip and azimuth.
Source Code
H
High Gain Seismometer
L
Low Gain Seismometer
M
Mass Position Seismometer
N
Accelerometer
P
Geophone, very short period seismometer with natural frequency 5 - 10 Hz or higher
Subsource Code - See Geographic orientation codes for more details.
N, E, Z
Traditional orientations of North (N), East (E), and Up (Z)
When within 5 degrees of true directions
1, 2, Z
Orthogonal components, nontraditional horizontals
1, 2, 3
Orthogonal components, nontraditional orientations
T, R
For rotated components or beams (Transverse, Radial)
A, B, C
Triaxial (Along the edges of a cube turned up on a corner)
U, V, W
Optional components, also used for raw triaxial output
Dip/Azimuth: Ground motion vector
Signal Units:
m,m/s,m/s**2
Tilt Meter¶
Measures tilt from the horizontal plane. Azimuth is typically N/S or E/W.
Source Code
A
Subsource Code - See Geographic orientation codes for more details.
N, E
Traditional orientations of North (N), East (E), and Up (Z)
When within 5 degrees of true directions
1, 2
Orthogonal components, nontraditional orientations
Dip/Azimuth: Ground motion vector
Signal Units:
rad(radian)
Creep Meter¶
Measures the absolute movement between two sides of a fault. Traditionally this has been done by means of fixing a metal beam on one side of the fault and measuring its position on the other side, but can also done with light beams, triangulation wires and other techniques.
The orientation and therefore the dip and azimuth would be perpendicular to the measuring beam, which would be along the average travel vector for the fault. Position/negative travel would be arbitrary, but would be noted in the dip/azimuth.
Source Code
B
Subsource Code
None defined
Dip/Azimuth: Along the fault or wire vector
Signal Units:
m(meter)
Calibration Input¶
Usually only used for seismometers or other magnetic coil instruments. This signal monitors the input signal to the coil to be used in response evaluation. Usually tied to a specific instrument. Sometimes all instruments are calibrated together, sometimes horizontals are calibrated separately from verticals.
Source Code
C
Subsource Code
A, B, C, D - For when there are only a few calibration sources for many devices.
Blank if there is only one calibrator at a time or, match calibrated channel (i.e. Z, N or E).
Pressure¶
A barometer, microbarometer, or other gauge that measures pressure. Used to measure atmospheric, water, and any other pressure. This includes infrasonic and hydrophone measurements.
Source Code
D
Subsource Code
O
Outside
I
Inside
D
Down hole
F
Infrasound
G
Deep sea differential pressure gauge
H
Hydrophone
U
Underground
Dip/Azimuth: For many pressure measurements Dip and Azimuth are not applicable. If the signal will be used for seismological applications, set Dip to -90 if a positive pressure change gives a positive signal, 90 if a positive pressure change gives a negative signal. This will align polarities with the vertical seismometer channel for UPGOING waves.
Signal Units:
Pa(Pascal)
Electronic Test Point¶
Used to monitor circuitry inside recording system, local power or seismometer. Usually for power supply voltages, or line voltages.
Source Code
E
Subsource Code
Designate as desired, make mnemonic as possible, use numbers for test points, etc.
Dip/Azimuth: Not applicable
Signal Units:
V(Volt),A(Ampere),Hz(Hertz), etc.
Magnetometer¶
Measures the magnetic field at the sensor location. They measure the part of the field vector that is aligned with the measurement coil. Many magnetometers are three axis. The instrument will typically be oriented to local magnetic north. The dip and azimuth should describe this in terms of the geographic north.
Example: Assuming magnetic north is 13 degrees east of north at the recording site, if the magnetometer is pointed to magnetic north, the azimuth would be + 103 for the E channel. Some magnetometers do not record any vector quantity associated with the signal, but record the total intensity. So, these would not have any dip or azimuth.
Source Code
F
Subsource Code
Z, N, E - Magnetic
Dip/Azimuth: Not applicable
Signal Units:
T(Tesla)
Humidity¶
Absolute/relative measurements of humidity. Temperature recordings may also be needed for meaningful results.
Source Code
I
Subsource Code
O
Outside environment
I
Inside building
D
Down hole
1, 2, 3, 4
Cabinet sources
–
All other letters for mnemonic source types.
Dip/Azimuth: Not applicable
Signal Units:
%(Percent)
Rotational Sensor¶
Measures solid-body rotations about an axis, commonly given in “displacement” (radians), velocity (radians/second) or acceleration (radians/second**2).
Source Code
J - Rotation rate sensor
Subsource Code - See Geographic orientation codes for more details.
N, E, Z
Traditional orientations of North (N), East (E), and Up (Z)
When within 5 degrees of true directions
1, 2, Z
Orthogonal components, nontraditional horizontals
1, 2, 3
Orthogonal components, nontraditional orientations
T, R
For rotated components or beams (Transverse, Radial)
A, B, C
Triaxial (Along the edges of a cube turned up on a corner)
U, V, W
Optional components, also used for raw triaxial output
Dip/Azimuth: Axis about which rotation is measured following right-handed rule.
Signal Units:
rad,rad/s,rad/s**2– following right-handed rule
Temperature¶
Measurement of the temperature at some location. Typically used for measuring:
Weather
Outside temperature
State of Health
Inside recording building
Down hole
Inside electronics
Source Code
K
Subsource Code
O
Outside environment
I
Inside building
D
Down hole
1, 2, 3, 4
Cabinet sources
–
All other letters for mnemonic source types.
Signal Units:
degC,°C,K
Water Current¶
Measurement of the velocity of water in a given direction. The measurement may be at depth, within a borehole or a variety of other locations.
Source Code
O
Subsource Code
None defined
Dip/Azimuth: Along current direction
Signal Units:
m/s(meter/second)Note
The special, administrative channel codes of L_O_G and S_O_H (both deprecated) do not denote water current and should be avoided when using the “O” Source Code.
Gravimeter¶
Measurement of a gravitational field.
Source Code
G - Gravitaional sensor
Subsource Code
Z - Traditionally 1 - Unknown, or not vertical**
Note: historically some channels from accelerometers have used a instrumentation code of G. As of August 2000 the FDSN defined the use of this code as limited to gravity.
Dip/Azimuth: Gravity field Vector
Signal Units:
m/s**2
Electric Potential¶
Measures the Electric Potential between two points. This is normally done using a high impedance voltmeter connected to two electrodes driven into the ground. In the case of magnetotelleuric work, this is one parameter that must be measured.
Source Code
Q
Subsource Code
None defined
Dip/Azimuth: Not applicable
Signal Units:
V(Volt)
Rainfall¶
Measures total rainfall, or an amount per sampling interval
Source Code
R
Subsource Code
None defined
Dip/Azimuth: Not applicable
Linear Strain¶
Dip/Azimuth are the line of the movement being measured. Positive values are obtained when stress/distance increases and negative when they decrease.
Source Code
S
Subsource Code - See Geographic orientation codes for more details.
N, E, Z
Traditional orientations of North (N), East (E), and Up (Z)
When within 5 degrees of true directions
1, 2, 3
Nontraditional orientations
Dip/Azimuth: Along axis of measurement
Signal Units:
m/m(meter per meter)
Tide¶
Measurement of depth of water at monitoring site. Not to be confused with lunar tidal filters or gravimeter output.
Source Code
T
Subsource Code
Z - Always vertical
Dip/Azimuth: Always vertical
Signal Units:
m(meter) - Relative to sea level or local ocean depth
Bolometer¶
Infrared instrument used to evaluate average cloud cover. Used in astronomy to determine observability of the sky.
Source Code
U
Subsource Code
None defined
Dip/Azimuth: Not applicable
Volumetric Strain¶
Source Code
V
Subsource Code
None defined
Dip/Azimuth: Not applicable
Signal Units:
m**3/m**3
Wind¶
Measures the wind vector or velocity. Normal notion of dip and azimuth does not apply.
Source Code
W
Subsource Code
S
Windspeed
D
Wind direction vector, relative to geographic north
H
Horizontal wind speed
Z
Vertical wind speed
Dip/Azimuth: Not applicable
Signal Units:
m/s
Derived or generated channel¶
Time series derived from observational data or entirely generated by a computer.
Warning
This code is deprecated. If no other Source code is applicable, a new code should be requested and allocated by the FDSN.
Source Code
X
Subsource Code
Similar to the observable data that was modified or the observable equivalent for generated time series (synthetics). See subsource codes for the corresponding observed channel.
Further Usage (DEPRECATED)
In order to document the provenance of the data, information must be available in the metadata for this channel that documents the algorithms, processes, or systems that modified or generated the time series. A channel comment, providing a Uniform Resource Locator (URL), must be included in the metadata. The information available at the URL must identify the processes that were applied to modify or generate the time series. This information must reference the FDSN web site (http://www.fdsn.org/x-instrument/).
Non-specific instruments¶
For instruments not specifically covered by an existing Source Code the Y Source Code can be used.
Warning
This code is deprecated. If no other Source code is applicable, a new code should be requested and allocated by the FDSN.
Source Code
Y
Subsource Code
Instrument specific.
Further Usage (DEPRECATED)
In order to document the instrument type and provenance of the data, information must be available in the metadata for this channel that documents the instrument that was used to generate the time series. A channel comment, providing a short description of the instrument, the type of measurement it makes and a Uniform Resource Locator (URL) referencing the FDSN web site (http://www.fdsn.org/y-instrument) that fully describes the instrumentation.
Synthesized Beams¶
This is used when forming beams from individual elements of an array.
Source Code
Z
Subsource Code
I
Incoherent beam
C
Coherent beam
F
FK beam
O
Origin beam
D
Wind direction vector, relative to geographic north
Dip/Azimuth: Ground motion vector
Signal Units:
m,m/s,m/s**2