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RDI ADCP Time Series

Data files for Teledyne RDI ADCPs are described here. Ancillary data (e.g., temperature, pitch, roll) are also available independently.

Revision History

  • 20110328: NetCDF, CF1.5 compliant product released.
  • 20110202: Correction for determination of ENU (with respect to true North) velocities. Prior code assumed ADCP was downward-facing. Updated code uses orientation or instrument to convert to ENU coordinates.
  • 20100521: Derived backscatter added to MAT contents.
  • 20100513: Initial NetCDF product released for RDI ADCPs, available in CF-1.4 compliant format.
  • 20100218: MAT contents made more complete and descriptive
  • 20091208: Initial PRF and MAT products released

Formats

This data is available in RDI, MAT and NETCDF formats. Content descriptions and example files are provided below.

RDI

This binary format is specific to the manufacturer. When using Teledyne-RDI data acquisition software, data is normally stored in this way. Although we use custom-built drivers to communicate with our instruments, we can use the raw data in the log file to produce the RDI file which can be interpreted by Teledyne-RDI post-processing software.

To produce the file, the following requirements apply:

  • A new RDI file is started at the beginning of each day, when the maximum records per file is exceeded, or when the driver is restarted (this should account for configuration changes, site changes, etc).
  • Only records with valid checksums are included.
  • The instrument date/time field is replaced using the NEPTUNE timestamp at the beginning of the log file (since this timestamp is more accurate than the instrument clock), and the checksum is recalculated.

This format is further described in the manufacturer's documentation.

Example: RDIADCP75WH3808_20101106T000225.rdi

MAT

MAT files (v7) can be opened using MathWorks MATLAB 7.0 or later. The file contains four structures: meta, adcp, config, and units.

meta: structure containing the following metadata fields.

  • deviceID: A unique identifier to represent the instrument within the NEPTUNE Canada network.
  • creationDate:Date and time (using ISO8601 format) that the data product was produced. This is a valuable indicator for comparing to other revisions of the same data product.
  • deviceHeading: Obtained at time of deployment (exception: for Device ID 13051, this field is NaN since this ADCP is on a mooring and does not have a fix heading).
  • siteName: Name corresponding to its latitude, longitude, depth position.
  • deviceName: A name given to the instrument.
  • deviceCode: A unique string for the instrument which is used to generate data product filenames.
  • locationName: The node of the NEPTUNE Canada observatory. Each location contains many sites.
  • samplingPeriod: Sampling rate of the instrument in seconds.
  • depth: Obtained at time of deployment.
  • lat: Obtained at time of deployment.
  • lon: Obtained at time of deployment.
  • dataProductVer: Version of data product.

adcp: structure containing the ADCP data, having the following fields.

  • range: vector of distance to each bin
  • corr: 3D matrix, correlation time-series for each bin
  • intens: 3D matrix, intensity time-series for each bin
  • velocity: 3D matrix, corresponds directly to output of instrument and so depends on configuration coordinate system
  • percentGood: 3D matrix, percent good time-series for each bin
  • ens: vector, ensemble number
  • compassHeading: vector, magnetic compass heading time-series
  • pitch: vector, pitch time-series
  • roll: vector, roll time-series
  • time: vector, timestamp in datenum format (obtained from time the reading reached the shore station)
  • temperature: vector, temperature time-series
  • salinity: vector or constant (depending if configured to be fixed or computed), salinity time-series
  • pressure: vector, pressure time-series
  • depth: vector, depth of the device as measured by the device for each ping. This will vary with the tide and more so if the device is mobile. It should be consistent with meta.depth.
  • soundSpeed: vector or constant (depending if configured to be fixed or computed), speed of sound time-series
  • uMagnetic (optional): 2D matrix, East velocity relative to magnetic North
  • vMagnetic (optional): 2D matrix, North velocity relative to magnetic North
  • u: 2D matrix, East velocity relative to True North
  • v: 2D matrix, North velocity relative to True North
  • w: 2D matrix, Upward Velocity
  • velocityError: 2D matrix, computed using RDI algorithm
  • backscatter: 3D matrix, includes two way beam spreading and absorption. The absorption computation follows Ainslie and Malcolm (1998; full reference details below). Absorption coefficient based on mean depth, temperature and salinity in adcp structure. Reference: Ainslie M. A., McColm J. G., "A simplified formula for viscous and chemical absorption in sea water", Journal of the Acoustical Society of America, 103(3), 1671-1672, 1998.

config: structure containing ADCP configuration details, where some field names are appended with '_XX' to represent the corresponding configuration command (beneficial for experienced RDI ADCP users).

  • fwVer: CPU firmware version
  • fwRev: CPU firmware revision
  • sysCfg: hardware configuration definition
  • freq: frequency
  • beamPattern: convex or concave
  • orient: orientation (e.g.,'Up' indicates transducers are looking upward)
  • beamAngle: beam angle
  • janusCfg: description of Janus Configuration
  • lagLength: time period between sound pulses
  • nbeams: number of beams
  • nbins_WN: number of bins
  • npings_WP: number of pings per ensemble
  • cellSize_WS: length per cell
  • profilingMode: sigal processing mode
  • corrThresh_WC: correlation threshold
  • codeReps: code repetitions in transmit pulse
  • percentGoodMin_WG: percent good threshold
  • errVelThreshold_WE: error velocity threshold
  • timePing_TP: time between pings within ensemble
  • coord_EX: coordinate transformation processing parameters
  • coordSys: coordinate system (evaluated from coord_EX)
  • headingAlign_EA: correction factor for physical heading misalignment
  • headingBias_EB: correction factor for electrical/magnetic heading bias
  • sensorSrc_EZ: defines selected source of environmental sensor data
  • sensorAvail: defines available sources of environmental sensor data
  • bin1Dist: distance to the middle of the first depth cell
  • transmitLength_WT: length of the transmit pulse
  • falseTrgt_WA: false target threshold
  • transmitLagDistance: distance between pulse repetitions
  • cpuSN: CPU board SN
  • sysBndwdth_WB: bandwidth setting (narrow or wide)
  • sysPower_CQ: system power setting
  • instSN: instrument serial number
  • ensInterval: ensemble interval
  • soundAbsorptionCoefficient: sound absorption coefficient used for computing backscatter
  • ambiguityVelocity_WV: radial ambiguity velocity

units: structure containing unit of measure for fields in structures above. For instance, units.pressure='decibar'.

For details about the configuration parameters, refer to the manufacturer documentation (especially the WorkHorse Commands and Output Data Format manual).

Example: RDIADCP75WH3808_20101106T000225.mat

NETCDF

NetCDF is a machine-independent data format offered by numerous institutions, particularly within the earth and ocean science communities. Additional resources are noted here.

The NetCDF file is basically a conversion from the above MAT file, so the variables and data contained within are much the same. One distinction is that the NetCDF is set up for quick plotting. As such, does not contain all of the ancillary variables contained in the MAT file, for example, the NetCDF files do not include adcp.pressure. RDI NetCDF files do contain additional variable called cellDepth which is calculated as meta.depth - adcp.range. cellDepth is the approximate water depth at which the measurement bins are located. It designated as the Z-axis for plotting purposes. The advantage of using the near-constants meta.depth and adcp.range in it's calculation is that plots made will be consistent. For mobile devices, it would be better to use the adcp.depth adcp.range variables for plotting. (Ancillary variables adcp.depth, adcp.range and adcp.temperature are included in the NetCDF file).

Example: RDI75_9202_20110201T000000Z.nc

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