First_bottom_length_normalized

First_bottom_length_normalized (m) is a bottom feature that may be extracted during bottom classification. A First_bottom_length_normalized analysis variable can be selected under Bottom on the Export page of the EV File Properties dialog box. It can be included with onscreen analyses and exported.

First_bottom_length_normalized represents the mean of the depth normalized length of the first bottom echo in the Feature extraction interval for a bottom classification.

where:

j	=	Bottom point in a bottom points variable. Bottom point number j is assigned sequentially in time. The pings of the echogram are partitioned according to the number of pings in a specified Feature extraction interval.
i	=	Ping i in the Feature extraction interval j.
First_bottom_lengthDepth Normalized i,j	=	Depth normalized length of the first bottom echo in ping i in Feature extraction interval j. The depth normalization equation is: First_bottom_lengthActual = Bottom line depth to the end of the first bottom echo at ping i in Feature extraction interval j. Refer to depth normalization algorithms for definitions of OffAxisPulseLengthRef, OffAxisPulseLengthActual.
n	=	The last ping in Feature extraction interval j.

See also

About bottom classification
Bottom classification algorithms
EV File Properties dialog box