SimradES70
-50dB
-70dB
-30dB
(CD010217-003)
TheBottomBackstepparameterallowsyouto
manuallymodifywhereonthebottompulsethe
depthshallbedetected.Thesettingdoesnothave
aneffectontheES70'sabilitytodetectandtrack
thebottom.
aThepeakofthebottompulse
bDefaultbottombacksteplevel
cApproximatebottombacksteplevelforatsh
detection
dApproximatebottombacksteplevelforseagrassdetection
Thebottompulsebasicallyidentiesthebottomdepthjustpriortothepeakofthe
pulse(A).However,thismaynotbethetruebottom.Forexample,ifthebottom
pulseisgeneratedbyarockbottomunderathicklayerofmud,theactualdepthis
slightlyshallower.Forthisreason,theES70isbydefaultsetuptogiveyouadepth
readingafewmillisecondsbeforethepeakofthepulse.Thisisdonebysettingthe
bottombackstepleveltoadefaultvalueof-50dB(B).
Theactualbottomwillneverappearatthepeakofthebottompulse(A),itwill
alwaysbeslightlybeforethepeak.BychangingtheBottomBackstepparameteryou
canhavethebottomdetectedearlier.Thisfeaturecanforexamplebeusedwhen
youshforatsh,orwhenyouareharvestingseagrass.
→Bottomslopesonpage288
Tip
IfyouuseanOlexsystem,youcantakeadvantageoftheBottomBackstepparameter
todetectseagrass.Decreasethebottombackstepvalue(makeitmorenegative)so
thatthebottomisdetectedatthetopofanareaofseagrass.TheOlexwillthen
detecttherealbottom,andtheresultistheheightoftheseagrass.
→Adjustingthebottomdetectiontondseagrassonpage73
Example27UsingtheBottomBackstepparameterforatshdetection
Ifyoushforsole,ounderorsimilarspecies,youcanusetheBottom
Backstepparametertoenhancethedetectionofthesh.Increasethebottom
backstepvalue(makeitmorepositive)sothatthebottomisdetectedslightly
deeperthanthecorrectdepth.TheES70willthen“pushthrough”thesh
better,andtheatshwillbeshownastheyarelocated“above”thebottom.
→Adjustingthebottomdetectiontondatshonpage72
5Applytoall
Clickthisoptionifyouwishtoimplementyourchangestoalltheechograms
presentlyinuseontheES70.
Relatedtopics
•Deningmaximumandminimumdepthsonpage72
•Adjustingthebottomdetectiontondatshonpage72
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