Nortek ADCP Ensemble-Averaged Time Series
15-minute ensemble-averaged data products for the Nortek ADCPs are described here. Information on the complete (non-averaged) time series are available here. The averaging process used is the simple box-car average with time stamps taken from the middle of the resample interval (7.5, 22.5, 37.5, 52.5 minutes past the hour for 15-min resampling), no other processing is done.
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This is no longer offered as a separate data product. It is now an option for the Nortek Time Series data product.
- 20121024: Initial Release
This data is available in MAT and NetCDF formats. The filename is appended with '-ENSEMBLE' to differentiate it from the MAT and NetCDF formats with the complete time-series. Content descriptions and example files are provided below.
To produce these files, the following requirements are similar to the non-averaged Nortek ADCP data products:
- A new file is started when the maximum records per file is exceeded (currently set to 35040, which is one year of data), or when there is a configuration, device or site changes.
- Only records with valid checksums, velocities less than 5 m/s*, correlations greater than 64 counts*, and not flagged are included. * - these thresholds may changed, the value used is stored in the MAT file.
- The instrument date/time field is replaced by 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.
- Instrument hardware, head and user configuration strings are important parameters are parsed into files. However, any data existing previous to accompanying configuration details being saved in the database cannot be interpreted (earlier than Fall 2009).
MAT files (v7) can be opened using MathWorks MATLAB 7.0 or later. The file contains four structures: meta, data, config, and units.
meta: structure containing the following metadata fields.
- deviceID: A unique identifier to represent the instrument within the NEPTUNE Canada observatory.
- 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: devices on mobile platform will have NaN since they do not have a fixed 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.
data: structure containing the ADCP data, having the following fields.
- time: vector, timestamp in datenum format (obtained from time the reading reached the shore station)
- range: vector of distance to start of each bin
- cellDepth: vector, starting depth of each cell calculated from range and deployment depth (may be inaccurate if instrument is vertically mobile)
- compassHeading: vector, magnetic compass heading time-series
- pitch: vector, pitch time-series
- roll: vector, roll time-series
- pressure: vector, pressure time-series
- temperature: vector, temperature time-series
- soundSpeed: vector or constant (depending if configured to be fixed or computed)
- voltage: vector, battery voltage time-series
- error: vector, error code
- pingsPerEnsemble: 2D matrix, the number of pings comprising the ensemble-average
- u,v,w: 2D matrices, East/North/Up velocities relative to True North, derived using raw velocity matrix, orientation, coordinate system, transformation matrix and one of a) calculated magnetic declination based on time and location (for mobile adcps) or b) meta.deviceHeading (fixed position ADCPs)
- velocity: 3D matrix, corresponds directly to output of instrument and so depends on configuration coordinate system
- amplitude: 3D matrix, amplitude time-series for each of the three receivers
- correlation: 3D matrix, signal correlation coefficient time-series for each of the three receivers (only available for HR-Profilers)
config: structure containing Nortek Aquadopp Profiler configuration details. For details about the configuration parameters, refer to the manufacturer documentation.
- SN: instrument type and serial number
- headSN: head serial number
- boardFrequency: board frequency
- headFrequency: head frequency
- fwVersion: firmware version
- hwRevision: hardware revision
- PICversion: PIC code version
- avgInterval: time the instrument is actively measuring within the profile interval
- measurementInterval: time between each measurement (i.e., data output rate)
- compassUpdateRate: rate at which compass readings are updated
- nbeams: number of transducers/beams.
- ncells: number of cells
- npings: number of pings per profile
- beamAngle: angle of beams
- blankingDistance: distance from the sensor head to the start of the first measurement cell. See Nortek forum discussion for calculation details.
- cellSize: size of each cell. See Nortek forum discussion for calculation details.
- coordSys: coordinates system of raw data (BEAM, XYZ or ENU)
- orientation: Up or Down indicates the direction transducers are facing
- transformationMatrix: matrix, used to convert from beam to xyz coordinates
- correlationThreshold: correlation threshold for resolving ambiguities (as per setting used on the device)
- velocityScaling: scaling for velocities from raw data, dependent on configuration
units: structure containing unit of measure for fields in structures above. For instance, units.pressure='decibar'.
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