Simrad Time Varied Gain (TVG) range correction

This page explains how time varied gain (TVG) range correction is applied to data from the following Simrad echosounders:

Ex500

The range values r are corrected according to following formula:

R = r - (3 * T + τ * 1470 / 4)

where:

R is the corrected range (m)

r the uncorrected range (m)

T is the sample thickness (m)

τ is the transmitted pulse duration (s) - also known as the pulse length

1470 is the sound speed Simrad value used by (m/s)

This correction is applied only if TvgRangeCorrection is set to SimradEx500 on the Calibration page of the Variable Properties dialog box, otherwise R = r.

Notes:

Echoview versions

TVG Range correction

1.51.xx

N/A

2.00.xx

R = r - (3 * T + τ * 1470 / 4)

2.10.00 to 2.10.09 (not released)

R = r - (3 * T + τ * 1470 / 4)

2.10.10 to 2.10.37

R = r - (2 * T + τ * 1470 / 4)

from 2.10.38

R = r - (3 * T + τ * 1470 / 4)

Ex60 (and ME70)

The range values r are corrected according to following formula:

R = r - cτ/4

where:

R is the corrected range (m)

r the uncorrected range (m)

c is the SoundSpeed (m/s) on the Calibration page of the Variable Properties dialog box.

τ is the TransmittedPulseLength (s) on the Calibration page of the Variable Properties dialog box.

This correction is applied when TvgRangeCorrection is set to SimradEx60 on the Calibration page of the Variable Properties dialog box. This correction only applies to SV variables.

Notes:

EK80

The range values r are corrected according to following formula:

R = r - cτ/4

where:

R is the corrected range (m)

r the uncorrected range (m)

c is the SoundSpeed (m/s) value on the Calibration page of the Variable Properties dialog box

τ is the TransmittedPulseLength (s) set on the Calibration page of the Variable Properties dialog box

This correction is applied when TvgRangeCorrection is set to SimradEK80 on the Calibration page of the Variable Properties dialog box.

This correction applies only to SV variables.

See also:

Simrad EK500 Power to Sv and TS
Simrad Ex60 Power to Sv and TS

Single target detection (single beam method 2)

Single target detection (split beam method 2)

Calibration page of the Variable properties dialog box
Single target detection page of the Variable properties dialog box
Background noise in Echoview
About time varied gain