This analysis variable shows the sum of the volumes of the analysis domain that were sampled in each ping.
The beam volume of a single ping within the analysis domain is calculated as:
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where
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= the two-way beam angle (steradians) | ||
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n
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= the number of boundaries, Ri, crossing the ping (-). See illustration below. | ||
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= |  |
0 if the samples in the interval interval between Ri and Ri+1 are in the analysis domain but are excluded from the analysis. |
| 1 otherwise, including below threshold data | |||
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R0
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= the range (measured along the beam axis of the ping) to the first sample in the analysis domain (m) | ||
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Rn
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= the range (measured along the beam axis of the ping) to the last sample in the analysis domain (m) |
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In the example below the samples in the ranges (R1 to R2), (R3 to R4), and (Rn-2 to Rn-1) are part of bad data regions and the volume of the beam in these ranges will not be included in the overall beam volume for the ping. The red hatching marks the samples which were analyzed - see analysis hatching for details.
The sum of the beam volumes of all pings in the analysis domain is calculated as:
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where:
N = The number of pings in the analysis domain being analyzed
Vp = The volume of ping p - as above (m3)
Notes:
Beam_volume_sum does not necessarily represent the sampled volume of water as the calculation does not take overlap between pings into account. This is of particular note in the case of a fixed transducer where two pings may represent sampling of the same volume of water.
To calculate the average number volume samples by all analyzed pings divide beam_volume_sum by the number of pings in the analysis domain.
This analysis variable was known as Volume_sampled in Echoview 3.00 and earlier and was only available for on-screen single target analyses.
Calculation of Beam_volume_sum 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.
