# Thickness_mean and Height_mean

The mean thickness of an analysis domain A defined as follows.

Let Ap be the set of pings p in the analysis domain, then:

Where:

 T = the mean thickness of the domain, Thickness_mean (m) Np = the number of pings in the analysis domain Notes: Np is not affected by any analysis settings. A ping is not included in the calculation when a cell or region extends above the first sample and the ping has no samples above the first sample. Prior to Echoview 9, such pings were included. A ping is not included in the calculation when a cell or region extends below the last sample and the ping has no samples below the last sample. Prior to Echoview 9, such pings were included. For more information refer to About samples and echo integration: Echo integration. tp = the thickness of ping p (m), calculated:

Note: There can be a difference in the thickness_mean of Sv echograms and single target echograms. The Sv algorithm is based on analyzed samples in the domain. The single target algorithm is based on exact range calculations in the domain.

1. #### For Sv echograms

Where:

 As = set of samples s in ping p in the analysis domain. Δtp = the thickness of one sample - that is, the sample spacing for ping p (m). = 0 if sample s is: above an Exclude above line and/or below an Exclude below line and/or is a no-data sample and Include the volume of no-data samples is not selected. Note: No-data samples may occur in a number of ways (no-data samples, samples within applied bad data (no data) regions and samples in pings with a bad line status). For further information refer to About analysis domains: Analysis based on regions and samples. 1 otherwise, including below threshold data.

#### For single target echograms

Where:

 NR = the number of boundaries crossing the ping (-). See illustration below. Ri = The range of boundary i in the ping (m). See illustration below. = 0 if the interval Ri ≤ R < Ri+1 is: above an Exclude above line and/or below an Exclude below line and/or is within a bad data (no data) region and Include the volume of bad data (no-data) regions is not selected 1 otherwise

Note: If an analysis domain contains no single targets, no value of thickness mean is calculated or exported. On the other hand, when an analysis domain does contain at least one single target, contributions to tp are included from intervals that are included in analysis but have no single targets within the interval.

An illustration of boundaries in a ping, for the purposes of calculating tp. The red hatching is the analysis-hatching.

## Height_mean (meters)

Height_mean is the projection of thickness_mean onto the vertical axis taking transducer geometry into account. For a vertically mounted transducer pointing directly downwards, Height_mean and Thickness_mean are equal.