Level 1 data (velocity point-measurements)
| Page status: Ready for review | |
|---|---|
| Author(s): | Cynthia |
| Reviewer(s): | |
| Comment: | |
The required dimensions and variables for the first processing level within NetCDF ATOMIX format for velocity measurements are described below. Note only a few attributes for each variable are listed since the page's purpose is to describe the information layout within each NetCDF file. Please refer to the complete list for the additional information required for writing the files.
Dimensions
The number of velocity instruments [N_VEL_INSTRUMENT] is here for completeness, but the benchmarks examples will have measurements only from one instrument stored.
| Short name | Standard name | Dimensions | Comments |
|---|---|---|---|
| TIME | time | time | Units in Days since 1950-01-01T00:00:00Z |
| TIME_HPR | time_of_heading_pitch_roll | TIME_HPR | Heading, pitch and roll (tilt) sensors measure always at 1Hz for Vector ADV |
| N_VEL_COMPONENT | number_of_velocity_components | N_VEL_COMPONENT | Maximum of 3 for u,v, w (east, north, up) velocities |
| Optional variables | |||
| N_VEL_INSTRUMENT | number_of_unique_velocity_instruments | N_VEL_INSTRUMENT | Required only if storing multiple synchronized instruments in the same file |
Variables
Required variables
| Short name | Standard name | Dimensions | Comments |
|---|---|---|---|
| [math]\displaystyle{ \ddagger }[/math] XYZ_VEL (or ENU_VEL/BEAM_VEL) | water_velocity_measured_in_instrument_coordinates | TIME, N_VEL_COMPONENT, N_VEL_INSTRUMENT | Other variables are water_velocity measured_in_geographical_coordinates(ENU) or measured_in_beam_coordinates (beam). |
| [math]\displaystyle{ \dagger }[/math] HEIGHT or DEPTH | See table below | TIME, N_VEL_INSTRUMENT | |
| [math]\displaystyle{ \dagger\dagger }[/math] BURST_NUMBER | unique_identifier_for_each_burst_in_this_file | TIME | Intergers of 1, 2, etc to designate which burst the velocities are associated with. |
| Platform motion variables | |||
| HEADING | platform_yaw_angle | TIME_HPR, N_VEL_INSTRUMENT | degrees, clockwise from true North |
| PITCH | platform_pitch_angle | TIME_HPR, N_VEL_INSTRUMENT | degrees |
| ROLL | platform_roll_angle | TIME_HPR, N_VEL_INSTRUMENT | degrees |
| Quality-control variables usually available with acoustic-Doppler instruments | |||
| ABSIC | backscatter_intensity_from_acoustic_beam | TIME, N_VEL_COMPONENT, N_VEL_INSTRUMENT | |
| SNR | signal_noise_ratio_from_each_acoustic_beam | TIME, N_VEL_COMPONENT | decibel |
| CORRN | noise_correlation_percent_from_each_acoustic_beam | TIME, N_VEL_COMPONENT, N_VEL_INSTRUMENT | |
| [math]\displaystyle{ \ddagger }[/math] Some manufacturers record quality-control variables (e.g., CORRN) in the instrument coordinate system. For example, Nortek records these variables in the instrument XYZ frame of reference. It's best to record the data in that coordinate system.
[math]\displaystyle{ \dagger }[/math] A variable situating the instruments in the water column is required. This may be a nominal depth (or height) or a time-varying depth or height above the bottom. [math]\displaystyle{ \dagger\dagger }[/math] Variable required only when measuring in bursts e.g., 18 min of continuous measurements every hour. | |||
Required height variable
Height or depth-related variables (only 1x is required). These variables locate the instrument vertically from a boundary (e.g, surface or ice). A negative value implies it's below the boundary. Units are always in meters.
| Short name | Standard name | Dimensions |
|---|---|---|
| HEIGHT_AB | height_above_bottom | TIME, N_VEL_INSTRUMENT |
| DEPTH | depth_below_surface | TIME, N_VEL_INSTRUMENT |
Optional Ancillary Variables
| Short name | Standard name | Dimensions | Comments |
|---|---|---|---|
| PRES | sea_water_pressure | TIME, N_VEL_INSTRUMENT | dbar, equals 0 at the sea surface and positive down. |
| *TEMP | sea_water_temperature | TIME | degrees_Celsius, in-situ temperature ITS-90 scale |
| *Data from concurrent sensors may be optionally included e.g., salinity, dissolved oxygen (e.g., eddy-correlation system). Kinematic viscosity of seawater needs to be calculated during processing, | |||
Group attributes (metadata)
This section describes attributes that may provide additional information about how the data was processed and manipulated at this stage.
| Attribute name | Purpose | Suggested content |
|---|---|---|
| processing_level | Boilerplate about the ATOMIX Level 1 content. |
|
| comment (optional) | Information is pertinent to problems in the raw data files during collection. | Examples: Stitching of files, corruption of binary files that were recovered by the manufacturer, etc. |
Go to next level: Level 2 quality controlled and segmented
