About no data

Echograms can contain areas which contain no data. These areas are termed "no data areas", and they contribute nothing to analyses. They commonly arise, for example, when the range over which data are collected changes during a survey (such as when the water depth changes). A no data area is a part of the echogram in which no samples are found.

There are also situations in which valid samples are associated with no value. These are termed "no data samples", and they also contribute nothing to analyses. This situation arises, for example, where data are masked in a virtual echogram or if thresholded values are set to "no data" on the Data page of the Variable Properties dialog box. A no data sample is a sample that has the value "no data".

Samples within defined Bad data (no data) regions are set to a value of no-data under the Analysis page setting Apply bad data regions. Under the setting Include the volume of no data samples, no data samples may be handled in two distinct ways during integration or analysis calculations. For more information refer to About samples and echo integration and About analysis domains.

Samples with the value "no data" are exported with a special export value.

The color with which no data areas and no data samples are displayed depends upon the color scheme in use. It is typically black.

Notes:

Virtual variables display no data values according to the selected color scheme. See Color schemes for more information.
Post Echoview 5.2, no data samples within bad data regions are deemed as bad_data_samples for integration and analysis results. Prior to Echoview 5.2, no data samples within bad data regions were counted as no_data_samples.

About no data

See also