Raymarine A series - Page 317

D1641-5
1
3
2
4
5
6
ItemDescription
1Falseecho
2Trueecho
3Passingship
4
Mastorfunnel
5
Trueecho
6Falseecho
MultipleEchoes
Multipleechoesarenotverycommonbutcanoccur
ifthereisalargetargetwithawideverticalsurfaceat
acomparativelyshortrange.Thetransmittedsignal
willbereectedbackandforthbetweenthetarget
andyourownship,resultinginmultipleechoes,
displayedbeyondtherangeofthetruetargetecho,
butonthesamebearing.
D1642-4
1
2
ItemDescription
1Trueecho
2Multipleechoes
BlindSectors
Obstructionssuchasfunnelsandmastsnear
theradarantennamayobstructtheradarbeam
andcauseradarshadowsor‘blindsectors’.If
theobstructionisrelativelynarrow,therewillbe
areductionofthebeamintensity,thoughnot
necessarilyacompletecut-off.However,forwider
obstructionstheremaybeatotallossofsignal
intheshadowarea.Theremayalsobemultiple
echoeswhichextendbehindtheobstruction.Blind
sectoreffectscannormallybeminimizedbycareful
selectionofthescannersitepriortoinstallation.
RainorSnowClutter
Theradarcanseeechoesfromrainorsnow.
Returnsfromstormareasandrainsquallsconsist
ofcountlesssmallechoesthatcontinuously
changesize,intensityandposition.Thesereturns
sometimesappearaslargehazyareas,depending
ontheintensityoftherainfallorsnowinthestorm
cell.Theimagesinthetablebelowshowhowthe
Raincontrolcanclearupthisclutter:
Rain
clutter
off
Rain
clutter
on
SeaClutter
Radarreturnsfromwavesaroundthevesselcan
clutterthecentreoftheradarpicture,makingit
difculttodetectrealtargets.Such‘seaclutter’
usuallyappearsasmultipleechoesonthedisplayat
shortrangescales,andtheechoesarenotrepetitive
orconsistentinposition.Withhighwindsand
extremeconditions,echoesfromseacluttermay
causedensebackgroundclutterintheshapeofan
almostsoliddisc.Seacluttercanbesuppressed
usingtheseacluttersettings.Theimagesinthe
tablebelowshowhowtheseacluttersettingscan
clearupsomeofthisclutter:
Sea
clutter
off
Sea
clutterin
auto
Radarapplication
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