Wedge_volume_sampled
This optional single target analysis export analysis variable calculates the volume Vp of a trapezoidal wedge formed by the analysis domain and distance traveled by the transducer along a cruise track, for each ping p.
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where
N = The number of pings in the analysis domain being analyzed
Vp = The wedge volume of a single ping p within the analysis domain (m3)
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where
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l |
= the length of the analysis domain as measured along the cruise track, see notes below (m) |
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ϕ
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= the across track beam angle. Beam angle parameters: 3dB beam angles discusses the relationship between the across track beam angle and the transducer beam angles and beam compensation. By default the value is represented by the MajorAxis3dbBeamAngle specified on the Calibration page of the Variable Properties dialog box. However, in situations where the across track beam angle is not the same as the MajorAxis3dbBeamAngle, the setting WedgeVolumeBeamAngle can be specified to override the MajorAxis3dBBeamAngle. |
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0 if the interval between Ri and Ri+1 is invalid in the analysis domain, i.e.,
Generally, for Single target analysis, do not select the Include the volume of bad data (no data) setting. Note: No-data samples may occur in a number of ways (no-data samples, samples within |
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Ri
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= the range (measured along the beam axis of the ping) to the start of the ith boundary in the analysis domain (m). Refer to the illustration for Beam_volume_sum. | ||
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Ri+1
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= the range (measured along the beam axis of the ping) to the end of the ith boundary in the analysis domain (m) |
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- Wedge_volume_sampled does not represent the sampled volume of water, but an approximation thereof with simplifying assumptions.
- Calculation of Wedge_volume_sampled assumes that the variable (or echogram) contains individual pings. The results of this calculation will not be valid for resampled, integrated or otherwise reduced pings.
- The calculation assumes straight line travel over the analysis domain, and a uniform vessel speed and ping rate. When there is no position or distance variable coincident with the data, the wedge volume sampled is zero.
- The distance l is estimated as the distance between two points P1 and P2 defined as follows:
- if there is a ping before the analysis domain then P1 is the position midway between the first ping in the analysis domain and the previous ping, otherwise P1 is the position calculated in this same manner assuming there is a ping before the analysis domain equally far from the first ping as is the second ping.
- if there is a ping after the analysis domain then P2 is the position midway between the last ping in the analysis domain and the next ping, otherwise P2 is the position calculated in this same manner assuming there is a ping after the analysis domain equally far from the last ping as is the second last ping.
- This algorithm is taken from Kieser and Mulligan (1984)
- Single target beam angle calculation prior to Echoview 13.1. See also the discussion in Single target beam volume angle prior to Echoview 13.1.
See also
About analysis domains
Beam_volume_sum
About single targets: Analysis
Beam angle parameters