Raymarine E70293 - Page 54

D6855-3
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ItemDescription
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Ahardbottom(sand)producesathinline.
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Asoftbottom(mudorseaweedcover)produces
awideline.
3Arockyorunevenbottomorawreckproduces
anirregularimagewithpeaksandtroughs.
Thedarklayersindicateagoodecho;thelighter
areasindicateweakerechoes.Thiscouldmeanthat
theupperlayerissoftandthereforeallowingsound
wavestopasstothemoresolidlayerbelow.
Itisalsopossiblethatthesoundwavesaremaking
twocompletetrips–hittingthebottom,bouncingoff
thevessel,thenreectingoffthebottomagain.This
canhappenifthewaterisshalloworthebottomis
hard.
Factorsinuencingthesonarimage
Thequalityandaccuracyofthedisplaycanbe
inuencedbyanumberoffactorsincludingvessel
speed,depth,objectsizeandbackgroundnoise.
Vesselspeed
Theshapeofthetargetchangesalongwithyour
speed.Slowerspeedsreturnatter,morehorizontal
marks.Higherspeedscausethetargettothicken
andarchslightly,atfastspeedsthemarkresembles
adoubleverticalline.
Targetdepth
Thecloserthetargettothesurface,thelargerthe
markonscreen.
Thedepthofindividualtargetscanbedisplayedby
switchingontheTargetDepthIDinthesonarmenu
Menu>DisplayOptions.Thenumberoftarget
depthsdisplayedisinuencedbytheshalarm
sensitivitylevel.
Waterdepth
Aswaterdepthincreasessignalstrengthdecreases,
resultinginalighteron-screenimageofthebottom.
Sizeofthetarget
Thelargerthetarget,thelargerthereturnon-screen.
Thesizeofashtargetisalsodependentuponthe
sizeofthesh’sswimbladderratherthanitsoverall
size.Theswimbladdervariesinsizebetween
differentbreedsofsh.
Clutter/Backgroundnoise
Thesonarimagemaybeimpairedbyechoes
receivedfromoatingorsubmergeddebris,
particulatematter(suchasplankton,phytoplankton,
orsiltetc.),airbubblesoreventhevessel's
movement.Thisisknownas‘backgroundnoise’or
‘clutter’andiscontrolledbytheSensitivitysettings.
Ifrequiredyoucanadjustthesettingmanually.
Fishnderapplications
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