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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, through scalar data products, see time series scalar data and time series scalar plots.

Oceans 2.0 API filter: dataProductCode=RADCPTS

Revision History

• 20150903: RDI files now use corrected heading/pitch/roll as specified by site and sitedevice meta data. RDI files with Earth co-ord data are rotated to the corrected heading or apply magnetic declination. These changes do not change the MAT/PNG/NC/PDF data products produced from RDI files other than the compassHeading/pitch/roll values within the MAT/NC files. These changes will allow RDI files to be made available.
• 20150601: Added bin-mapping options (None, nearest vertical, linear).
• 20150228: Depth cell / bin mapping added to correct range and velocity for tilt.
• 20141222: Heading correction rework (affecting ENU / uvw velocities): handle sites with null positions, mobile sensors, autonomous deployments, and better documentation of processing was done to the data.
• 20130317: Bug fixes, including making the number of dimensions of data structures fixed (trailing singleton dimensions are always dropped in MATLAB however).
• 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 RDI and MAT products released

Formats

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

Manufacturer's Raw Binary Format: .RDI Files

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.
• For Beam or Instrument co-ordinate data, heading/pitch/roll (EH/EP/ER) data in the variable length data header are replaced as specified by site and sitedevice metadata (replacing the often unreliable onboard compass) (the EZ sensor source value is changed to manual for each). For Earth co-ordinate data, only the heading is updated with the value from the site and sitedevice metadata, if the internal compass sensor is used, it is corrected for magnetic declination, else if the internal heading value is set manually, it is left alone. Also for Earth data, because the heading has changed, the North/South current velocities are rotated to the new heading. These changes do not change the velocities in the MAT/PNG/NC/PDF data products produced from RDI files, other than the compassHeading/pitch/roll values within the MAT/NC files. The original magnetic compass, pitch and roll maybe replaced by these fixed or external sensor values, however, users can access the original sensor data via scalar data products and services. 

For users' information and interest, the site and sitedevice information is available through the device details pages, for example: http://dmas.uvic.ca/DeviceListing?DeviceId=20003. This information is also included in the metadata report that accompanies most data products.

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

Example: RDIADCP75WH17432_20131113T000000.000Z.rdi

Oceans 2.0 API filter: extension=rdi

Processed Data

Data Product Options: Ensemble averaging

MAT Files

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

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

• range: vector of distance to each bin centre. If bin mapping compensation for tilt is active, this is then a vertical range to the bin centres, see adcp.processingComments to see if bin mapping was applied. To calculate the depth of each velocity bin, use the following:  

  if strcmp(Config.orient, 'Up')
    binDepth = Meta.depth - ADCP.range;
else
    binDepth = Meta.depth + ADCP.range;
end

• corr: 3D matrix, correlation time-series for each bin
• intens: 3D matrix, intensity time-series for each bin (also known as received signal strength intensity or RSSI)
• 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 (replaced ensFirst for averaged products)
• ensFirst: vector of the first ensemble number in an ensemble average (averaged products only, replaces ens).
• compassHeading: vector, containing the EH values from the RDI files. This is either the fixed value from site and sitedevice headings (if not null), or values from an assigned true heading mobile position sensor. If neither, then it defaults to the magnetic compass heading data.
• pitch: vector, containing the EP values from the RDI files. This is either the fixed value from site and sitedevice headings (if not null), or values from an assigned true heading mobile position sensor. If neither, then it defaults to the onboard pitch sensor data.
• roll: vector, containing the ER values from the RDI files. This is either the fixed value from site and sitedevice headings (if not null), or values from an assigned true heading mobile position sensor. If neither, then it defaults to the onboard roll sensor data.
• time: vector, timestamp in datenum format (obtained from time the reading reached the shore station)
• temperature: vector, temperature time-series
• salinity: vector salinity time-series, (may contain constant values depending on device configuration)
• 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. However, it may be in error. If any disagreement, take the value from meta.depth.
• soundSpeed: vector speed of sound time-series, (may contain constant values depending on device configuration)
• uMagnetic (optional): 2D matrix, East velocity relative to magnetic North
• vMagnetic (optional): 2D matrix, North velocity relative to magnetic North
• processingCommments: a string documenting all of the processing steps done to produce adcp.u/v/w. Use char(adcp.processingComments) to print out the text.
• velocity_sourceInfo: a string describing the source of data in adcp.velocity
• uvw_sourceInfo: a string describing the resulting final, rotated data in adcp.u/v/w
• u: 2D matrix, East velocity relative to True North
• v: 2D matrix, North velocity relative to True North
• w: 2D matrix, Upward Velocity
• u_std, v_std, w_std: standard deviations for ensemble averaged u,v,w (averaged products only)
• u_count, v_count, w_count: the number of ensembles/pings that contributed to u,v,w (averaged products only). Differs from pingsPerEnsemble in that it accounts for filtered / NaN-ed data
• velocityError: 2D matrix, computed using RDI algorithm
• backscatter: 3D matrix based on received signal strength intensity (adcp.intensity), compensated for two-way spreading (20LogR) and absorption. Equation based on Gostiaux and van Haren ("Extracting Meaningful Information from Uncalibrated Backscattered Echo Intensity Data, Journal of Atomsheric and Oceanic Technology, 72, 943-949, 2010). The absorption computation follows Ainslie and Malcolm ("A simplified formula for viscous and chemical absorption in sea water", Journal of the Acoustical Society of America, 103(3), 1671-1672, 1998). Absorption coefficient based on mean depth, temperature and salinity in adcp structure.
• meanBackscatter: same as above, except averaged over the four beams to create a 2D matrix. Averaging is done by converting to standard intensity, averaging, then converting back to decibels.

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
• heading_EH: manual setting of the heading from device attributes (not in RDI file, added after)
• 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 (not in RDI, added after)

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

Oceans 2.0 API filter: extension=mat

NETCDF Files

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 extracted from the data contained in the above MAT file. The NetCDF file contains the following variables: u, v, w, time, depth, latitude, longitude and temperature. Important: the depth variable here is distinct from the pressure sensor measurement in the MAT file (adcp.depth). The NetCDF depth variable is is calculated as meta.depth - adcp.range; it 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 the calculation is that plots made will be consistent. For mobile RDI ADCPs, it is necessary to use the adcp.depth and adcp.range variables for plotting. Unfortunately, the CF convention does not permit these additional variables, so use the MAT file in this rare case.

Example: BC_POD3_ADCP_20120214T175028.546Z.nc

Oceans 2.0 API filter: extension=nc

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