HTI splitbeam beam compensation
Splitbeam beam compensation in Echoview is based upon an algorithm employed by HTI.
Settings
When HTI beam compensation is selected under Beam compensation model on the Single Target Detection page of the Variable Properties dialog box, the following additional settings are available:
Setting

Description

HTI beam pattern factor coefficients

Displays the Beam pattern factor coefficients for a fourthorder polynomial fit to an ideal beam pattern.
You can enter the coefficients yourself or Echoview can read the coefficients from the data files for the first suitable HTI variable found, when Set HTI coefficients from file is selected.
Note: Entering your own polynomial coefficients may have a dramatic effect on target strength. HTI recommend using the coefficients supplied with each transducer. (pers .comm HTI management)
The following coefficients are offered:
Vertical coefficients for the minoraxis beam pattern factor
Horizontal coefficients for the majoraxis beam pattern factor

Set HTI coefficients from file

When selected, Echoview reads the coefficients from data file for the first suitable HTI variable found.

Clear

Sets all beam pattern coefficients to zero.

HTI splitbeam beam compensation algorithm
HTI splitbeam beam compensation is applied to targets identified by the Single Target Detection algorithms (splitbeam methods).
In splitbeam systems the beam compensation equation can be written as function of beam position as follows:
TS(α,β) = TS(0,0) + B(α,β)
where:
α

is the measured minoraxis angle of the target echo (degrees)

β

is the measured majoraxis angle of the target echo (degrees)

TS(0,0)

is the TS derived from received power measurements  valid at α=0, β=0 (dB re 1 m2)  see uncompensated_TS

TS(α,β)

is the TS predicted for a target at position α, β in the beam (dB re 1 m2)  see compensated_TS

B(α,β)

is the beam compensation function (dB). This identical to CorrHTISplitBeam

HTI beam compensation is calculated using the beam pattern characteristics of the transducer and the angular position of the target.
The beam pattern characteristics of HTI transducers are measured during calibration and remain constant. The HTI beam compensation algorithm uses a fourthorder polynomial to model an ideal beam pattern. The coefficients for the polynomial can be read from a HTI data file or you can enter your own values.
B(α,β) = B(α) + B(β)
where:
B(α) 
is the beam pattern factor in the plane of the minoraxis (dB)
where:
where:
α

= 
Minoraxis angle of the peak amplitude for the detected single target (mechanical degrees)
Note: The angular position variable (made up of minoraxis and majoraxis angles) is derived from values read from the HTI data file.

av

= 
is zero.

bv

= 
Parameter 225 from the first HTI data file found when you select Set HTI coefficients from file on the Single Target Detection page of the Variable Properties dialog box.
 OR 
The value for b entered under the Vertical HTI beam pattern factor coefficients section on the Single Target Detection page of the Variable Properties dialog box.

cv

= 
Parameter 226 from the first HTI data file found when you select Set HTI coefficients from file on the Single Target Detection page of the Variable Properties dialog box.
 OR 
The value for c entered under the Vertical HTI beam pattern factor coefficients section on the Single Target Detection page of the Variable Properties dialog box.

dv

= 
Parameter 227 from the first HTI data file found when you select Set HTI coefficients from file on the Single Target Detection page of the Variable Properties dialog box.
 OR 
The value for d entered under the Vertical HTI beam pattern factor coefficients section on the Single Target Detection page of the Variable Properties dialog box.

ev

= 
Parameter 228 from the first HTI data file found when you select Set HTI coefficients from file on the Single Target Detection page of the Variable Properties dialog box.
 OR 
The value for e entered under the Vertical HTI beam pattern factor coefficients section on the Single Target Detection page of the Variable Properties dialog box.


B(β) 
is the beam pattern factor in the plane of the majoraxis (dB)
where:
where:
β

= 
Majoraxis angle of the peak amplitude for the detected single target (mechanical degrees)
Note: The angular position variable (made up of minoraxis and majoraxis angles) is derived from values read from the HTI data file.

ah

= 
is zero. 
bh

= 
Parameter 230 from the first HTI data file found when you select Set HTI coefficients from file on the Single Target Detection page of the Variable Properties dialog box.
 OR 
The value for b entered under the Horizontal HTI beam pattern factor coefficients section on the Single Target Detection page of the Variable Properties dialog box.

ch

= 
Parameter 231 from the first HTI data file found when you select Set HTI coefficients from file on the Single Target Detection page of the Variable Properties dialog box.
 OR 
The value for c entered under the Horizontal HTI beam pattern factor coefficients section on the Single Target Detection page of the Variable Properties dialog box.

dh

= 
Parameter 232 from the first HTI data file found when you select Set HTI coefficients from file on the Single Target Detection page of the Variable Properties dialog box.
 OR 
The value for d entered under the Horizontal HTI beam pattern factor coefficients section on the Single Target Detection page of the Variable Properties dialog box.

eh

= 
Parameter 233 from the first HTI data file found when you select Set HTI coefficients from file on the Single Target Detection page of the Variable Properties dialog box.
 OR 
The value for e entered under the Horizontal HTI beam pattern factor coefficients section on the Single Target Detection page of the Variable Properties dialog box.


Note: HTI beam pattern factor coefficients in the file can be viewed via a TS echogram and selecting Show Information on the Shortcut menu.
See also
About single target detection
Single target detection algorithms
Single target detection (split beam method)
HTI Sample data to Sv, TS and angular position