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Trawlsensorsystems(typicallySimradITIandPI)communicateheadropedepth,as
wellasthedistancefromtheheadropetothefootrope(trawlopening),totheES70at
regularintervals.Thisinformationisrequiredforthetrawlechogramtobegenerated.
Withoutthedepthoftheheadrope,theechogramwillappearlikeastandardpelagic
echogramcontrolledbytheRangeandStartRangeparameters.
Thedistancefromtheheadropetothefootrope(trawlopening)canbemanuallyset
intheTrawldialog.Thisisusefulfortrawlsensorsystemsnotmeasuringthetrawl
opening,orwhenthemeasureddistanceisunreliable.TheTrawldialogalsoallowsyou
toenterthedistancefromthevesseltothetrawlopening.Thedepthoftheheadrope
musthoweverbeprovidedbythecatchmonitoringsystem.
IntheTrawldialogyoucanalsodenethedistancefromthevesseltothetrawlopening.
Example12StartRangeandRangeinatrawlechogram
Inatrawlechogram,settheStartRangevalueto–5meters.Thiswillmakethe
echogramstartfrom5metersabovetheheadrope.Ifthetrawlopeningis20
meters,setRangeto30meters.Theechogramwillnowshowtheareafrom5
metersabovetheheadrope,downacrossthetrawlopening,anddownto5meters
belowthefootrope.Onapelagictrawl,thebottomcontourisnormallynotshown
withthesesettings.Onabottomtrawl,thebottomcontourisshownoncethetrawl
openingislessthan5metersoverthebottom.
ThebiomasscalculationsinaTrawlechogramarenotrestrictedbythebottomdetection.
Thismeansthatthebottomechowillbeincludedinthecalculationsifitappearswithin
thechosenrange.
Relatedtopics
•StartRangeonpage160
•Rangeonpage158
•CalculationIntervalonpage192
•Echogramonpage220
Echogrammarkers
TheechogramsprovidedbytheES70maycontainadditionalinformation.Thefollowing
lines,markersandannotationscanbeenabled.
Topics
•Bottomlineonpage130
•Whitelineonpage130
•Hardnesslineonpage131
•Trawllineonpage131
•Variabledepthlineonpage132
•Rangeotherlinesonpage132
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