About analysis domains

An analysis domain defines the inital set of datapoints (samples) or single targets (echoes) to be considered for analysis. In Echoview, an analysis domain may be defined for:

Echograms (for single beam data)
Scenes (for multibeam data)

Note: Analysis settings can direct Echoview to exclude specific samples and pings from analyses.

Analysis domains on echograms (for single beam data)

An analysis domain can be defined for single beam data on echograms by:

Which pings and samples are included in an analysis domain

Pings and samples with time/distance coordinates that are inside the boundary of the analysis domain are included in the analysis domain.

Pings and samples with time/distance coordinates that place them on a boundary of the analysis domain are treated as follows:

If the ping or sample is on the...	Then...
left boundary	it is included in the analysis domain
right boundary	it is not included in the analysis domain

Samples with depth coordinates that are inside the boundary of the analysis domain are included in the analysis domain.

Samples with depth coordinates that place them on a boundary of the analysis domain are treated as follows:

If the sample is on the...	Then...
upper boundary	it is included in the analysis domain
lower boundary	it is not included in the analysis domain

Notes:

selections, 2D regions and cells are all defined in time/depth coordinates.
Lines in Echoview have a higher precision than Sv sample ranges and thus the boundaries of an analysis domain may not lie on sample boundaries.

Exclusions from analyses

Samples that are included in an analysis domain will be excluded from analyses of that domain if they are:

within a bad data region and Exclude bad data regions is selected on the Analysis page of the Variable Properties dialog box,
below an Exclude-below line (if one is defined),
above an Exclude-above line (if one is defined),
above a point on the currently selected exclude-below line which has bad line status and Exclude pings with bad line status on the exclude below line is selected on the Analysis page of the Variable Properties dialog box
no data values

A sample that is excluded from analysis is not included in the calculations for onscreen analysis or export analysis. Excluded samples (from analysis) reduce the Thickness_mean which is used in the calculations for NASC except in the case where Whole excluded or no-data pings do not reduce the Thickness mean is selected on the Analysis page of the Variable Properties dialog box. It is important to understand the ramifications of excluded samples in the reporting of NASC and the estimation of biomass. For more information refer to About samples and echo integration.

Note: Excluded samples do not alter the definition of the analysis domain itself. The analysis domain's boundaries remain unchanged. These exclusions apply to the analysis of samples within the analysis domain.

Viewing good datapoints

The set of datapoints that fall within an analysis domain and are not excluded, are termed good datapoints.

When you perform an on-screen integration or an on-screen analysis of an analysis domain, all good datapoints will be overlayed with analysis-hatching (providing that the Show Analysis option on the Echogram page of the EV File Properties dialog is selected).

You can view the good data points for an entire echogram using the Processed Data operator. This operator creates a virtual echogram which displays only the good datapoints for an echogram.

You can view information about a datapoint as follows:

To view time information about a datapoint, move the mouse point over the datapoint and check the status bar.
To view depth and range information about a datapoint, invoke the Information dialog box and select the Datapoint page (or Target page for a single target detection).

Analysis domains on scenes (for multibeam data)

An analysis domain can be defined for multibeam on scenes by:

a 3D region

Which datapoints are included in an analysis domain

Datapoints are included in an analysis domain if:

the latitude, longitude and depth coordinates of the datapoint are inside the boundary of the analysis domain, and
the time of the ping on which the datapoint is, lies within the valid time of the analysis domain

Datapoints with latitude, longitude and depth coordinates that place them on the boundaries of the analysis domain are highly unlikely to occur and inclusion is undefined in this circumstance.

Datapoints cannot be excluded from analysis domains on scenes. It is possible however to detect 3D schools using exclusion criteria. This will define a 3D region (domain boundary) which does not include this data.