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- time: vector, timestamp in datenum format (obtained from time the reading reached the shore station, or if the ping averaging option was selected, these time stamps will be resampled).
- temperature: vector, temperature time-series (will be filled with NaNs if not available). Calibration formula:
vin = tempRawCounts * 2.5 / 65535;
R = (ka + kb * vin) / (kc - vin);
temperature = (1/(A + B * log(R) + C * (log(R)^3))) - 272.15; - pressure: vector, pressure time-series (will be filled with NaNs if not available). Note: calibration not yet available, these sensors are not calibrated or even connected, do not use this data.
- tiltX: vector, tilt X-direction time-series (will be filled with NaNs if not available). Calibration formula:
X_a * txc + X_b * txc + X_c * txc + X_d, where txc is the raw tilt counts in the x direction - tiltY: vector, tilt Y-direction time-series (will be filled with NaNs if not available). Calibration formula:
Y_a * txc + Y_b * txc + Y_c * txc + Y_d, where txc is the raw tilt counts in the x direction - voltage: vector, battery voltage time-series (will be filled with NaNs if not available)
- timeInstrumentClock: vector, instrument clock time-series
- ProfileNum: vector, profile number
- error: vector, error code
- nPingsAquired: vector, number of pings acquired for profile
- pingFirst: vector, index of first ping acquired in profile
- pingLast: vector, index of last ping acquired in profile
- profileStatus: vector, profile status code
- overrun: vector, (we think) this indicates if the data hit the limit of the A/D converter.
- Channel: structure (one for each channel, so access is by Data.channel(3) for example), with the following fields:
- rangeToBinCentre: vector of length of the number of bins. The range to the centre of each bin is calculated from two-way travel time, accounting for sound speed, lockout distance and one half of the pulse length.
- profileData: 2D matrix (time, rangeToBinCentre) of the acoustic data. The acoustic data can be raw counts from the echosounder's Analogue to Digital converter (A/D), or if calibrated, it will be Volume Backscatter or Target Strength data in units of dB re 1 m-1 or dB re 1 m2 (respectively). See the Unit structure or the isCalibrated flag (below) in order to tell the two apart. Here is the calibration formula applied to convert raw profile data to calibrated profile Volume Backscatter (Sv) data for AWCPs and AZFPs:
N = (log10(Data.Channel(i).profileData) - 2.5) * 524280 * Config.Calibration.DS(i);
Data.Channel(i).profileData = Config.Calibration.EL(i) - 2.5/Config.Calibration.DS(i) + ...
N/(26214*Config.Calibration.DS(i)) - Config.Calibration.TVR(i) - 20*log10(Config.Calibration.VTX0(i)) + 20*log10(R) + ...
2*Config.Calibration.acousticAttenuation(i) * R - ...
10*log10( (1/2) * Config.speedOfSound * (Config.pulseLength(i)*1e-6) * Config.Calibration.BP(i) );
Here is the calibration formula for ZAPs:Data.Channel(i).profileData = -Config.Calibration.OCV(i) - Config.Calibration.sourceLevel(i) - 20*log10(Config.Calibration.Q(i)) + 20*log10(R) +...
2*Config.Calibration.acousticAttenuation(i) * R -...
10*log10( (1/2) * Config.speedOfSound * (Config.pulseLength(i)*1e-6) * Config.Calibration.BP(i) ) +...
20*log10(Data.Channel(i).profileData) - repmat(Config.Calibration.zapInterpTVG(i,:), size(Data.Channel(i).profileData, 1), 1);
where i is the channel number and R is the rangeToBinCentre (replicated into a matrix). The calibration procedure also accounts for the gain and time-varying-gain applied. In the case of the ZAP echosounder, an optional noise reduction algorithm is also applied (contact us for more details). To calculate the Target Strength (TS, units of dB re 1 m2,) the 20logR term becomes 40logR and the ensonification term is dropped (the term with the beampattern BP and pulse length), as detailed here: EchoViewManual_AZFP_Sv_and_TS.pdf
- rawData: 2D matrix (time, rangeToBinCentre) of the acoustic data. When non-calibrated data is requested for ZAP echosounders only, this matrix is provided as the most raw data. In that case, profileData represents the noise-reduced raw data (contact us for more details).
- isCalibrated: integer, 0 indicates the data is not calibration, 1 indicates volume backscatter data in units of dB re 1 m-1, 2 indicates Target Strength in units of dB re 1 m2. Calibration may be requested but no provided if not available. This flag represents what the data is, not what was requested.
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