Raymarine c97 Installation And Operation Handbook

14.2Thesonarimage
Interpretingtheseabedusingsonar
Itisimportanttounderstandhowtocorrectlyinterprettheseabed
structurerepresentedintheshnderdisplay.
Theseabedusuallyproducesastrongecho.
Thefollowingimagesshowhowdifferentseabedconditionsare
representedinthesonardisplay:
D6855-3
1
2
3
ItemDescription
1
Ahardbottom(sand)producesathin
line.
2
Asoftbottom(mudorseaweedcover)
producesawideline.
3Arockyorunevenbottomorawreck
producesanirregularimagewith
peaksandtroughs.
Thedarklayersindicateagoodecho;thelighterareasindicate
weakerechoes.Thiscouldmeanthattheupperlayerissoftand
thereforeallowingsoundwavestopasstothemoresolidlayer
below.
Itisalsopossiblethatthesoundwavesaremakingtwocomplete
trips–hittingtheseabed,bouncingoffthevessel,thenreecting
offtheseabedagain.Thiscanhappenifthewaterisshallow,the
seabedishard,orthegainissettohigh.
Factorsinuencingthesonardisplay
Thequalityandaccuracyofthedisplaycanbeinuencedbya
numberoffactorsincludingvesselspeed,depth,objectsize,
backgroundnoiseandtransducerfrequency.
Vesselspeed
Theshapeofthetargetchangesalongwithyourspeed.Slower
speedsreturnatter,morehorizontalmarks.Higherspeedscause
thetargettothickenandarchslightly,untilatfastspeedsthemark
resemblesadoubleverticalline.
Targetdepth
Thecloserthetargettothesurface,thelargerthemarkonscreen.
Thedepthofindividualtargetscanbedisplayedbyswitchingonthe
TargetDepthIDintheshndermenuMenu>Presentation.The
numberoftargetdepthsdisplayedisinuencedbytheshalarm
sensitivitylevel.
Waterdepth
Asseadepthincreasessignalstrengthdecreases,resultingina
lighteron-screenimageofthebottom.
Sizeofthetarget
Thelargerthetarget,thelargerthereturnontheshnderdisplay.
Thesizeofashtargetisalsodependentuponthesizeofthesh’s
swimbladderratherthanitsoverallsize.Theswimbladdervariesin
sizebetweendifferentbreedsofsh.
Transducerfrequency
Thesametargetwillappeardifferentlywhenthetransducer
frequencyischanged.Thelowerthefrequencythebroaderthe
mark.
Clutter/Backgroundnoise
Theshnderpicturemaybeimpairedbyechoesreceivedfrom
oatingorsubmergeddebris,airbubblesoreventhevessel’s
movement.Thisisknownas‘backgroundnoise’or‘clutter’andis
controlledbythegainmodes.Thesystemwillautomaticallycontrol
thegainsettingsaccordingtothedepthandwaterconditions.You
canhoweveradjustthegainsettingsmanuallyifyouprefer.
Usingtheshnder
159

Raymarine c97 Specifications

General

Brand	Raymarine
Model	c97
Category	Marine GPS System
Language	English