R/V Kilo Moana EM122 Multibeam Echosounder …mac.unols.org/sites/mac.unols.org/files/KM1514_MAC_Final...R/V Kilo Moana EM122 Multibeam Echosounder Review KM1514 - August 9-13, 2015

R/VKiloMoanaEM122MultibeamEchosounderReviewKM1514-August9-13,2015

Reportpreparedby:PaulJohnsonandKevinJerramUniversityofNewHampshireCenterforCoastalandOceanMapping/JointHydrographicCenterDurham,NHVickiFerriniLamont-DohertyEarthObservatoryColumbiaUniversityPalisades,NY

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TableofContents

TableofContents...................................................................................................................2Introduction...........................................................................................................................3SurveySystemComponents...................................................................................................4

EM122..............................................................................................................................................4EM710..............................................................................................................................................4MRU.................................................................................................................................................4SoundSpeed.....................................................................................................................................4

KM1514Activities..................................................................................................................4EM122AccuracyTesting.........................................................................................................5

Overview..........................................................................................................................................6EM122AccuracyTestingResults.......................................................................................................7

EM122AchievedCoverage....................................................................................................10ConclusionsandRecommendations......................................................................................12Anyopinions,findings,andconclusionsorrecommendationsexpressedinthismaterialarethoseoftheauthor(s)anddonotnecessarilyreflecttheviewsofUNHorNSF.Cover:BathymetryfromtheEM122accuracyandextinctiontestingcollectedsouthwestofOahu.DatawereprocessedwithQPSQimeraandareshownfordisplaypurposesonly.

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IntroductionTheR/VKiloMoanaundertookanengineeringshakedownleg(KM1514)inordertoassessacousticnoiseissuesdocumentedduringtheKM1505QualityAssessmentVisit(QAT)conductedbytheMultibeamAdvisoryCommittee(MAC)inApril,2015anddocumentedinthatreport(seeR/VKiloMoana,EM122andEM710MultibeamEchosounderSystemReview,KM1505April28–30,2015).UndertakingthisassessmentwereVickiFerriniandPaulJohnsonastheMACQualityAssessmentTeam,TimGatesandMarisaYeartaastheNoiseAssessmentTeam,ScottFergusonrepresentingtheUniversityofHawaii’sOceanTechnologyGroup(OTG),andChuckHohingandTravisEliasenrepresentingKongsbergMaritime.

Figure1.Redlineshowstheshiptrackforthe2015EM122multibeamsystemtesting.Greentracklinesareshiptracksforthe2012shipboardacceptancetests.

FollowingtheKM1505leg,itwasrealizedbytheKiloMoana’sengineersandOTGpersonnelthatmountsfortheship’sgeneratorshadbeenchangedandapparentlyinstalledincorrectlyduringthespring’s2015shipyardperiod.Duringtheearlypartofthesummerof2015thesemountswerecorrectlyreinstalledandthentunedtominimizetransmissionofgeneratorvibrationtothehull.Withthisinmind,theabovepersonnelsetoutto1.)verifythattheship’sselfnoisehadreturnedtoitspreviouslymonitoredlevelsasdocumentedin2012,and2.)assesstheswathbathymetrycoverageandaccuracyoftheKiloMoana’sEM122.Forthisleg,datatoassessboththeseconditionswerecollectedsouthwestofHonolulufromAugust9-13,2015(Figure1).Thisreportpresents:

• abriefdescriptionofthetestingundertakenduringKM1514• swathcoverage/extinctiondatafortheEM122MBES• accuracyresultsfortheEM122

DetailedresultsanddiscussionoftheacousticnoisetestingcanbefoundintheKiloMoana2015AcousticTestReportsubmittedbyGatesAcoustictotheMACandwillnotbediscussedinthisreport.

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SurveySystemComponentsTheR/VKiloMoana’smappingsystemsconsistofthefollowingprimarycomponents:

EM1221. KongsbergMaritimeEM122multibeamechosounder(12kHz),v1.3.2,s/n1092. KongsbergMaritimeSeafloorInformationSystem(SIS),v4.1.3

EM7103. KongsbergMaritimeEM710multibeamechosounder(70-100kHz),v2.5.3,s/n2194. KongsbergMaritimeSeafloorInformationSystem(SIS),v4.1.5

MRU5. ApplanixPOS/MV-320v4MRU,s/n23196. TrimbleBD950GPSreceivers

SoundSpeed7. AMLOceanographicsurfacesoundspeedsensor8. Sippicanexpendablebathythermograph(XBT)profilingsystem

KM1514ActivitiesTheKM1514leghadthreemaingoals:1.)testingoftheUniversityofHawaii’sDeepOceanExplorationandResearchremotelyoperatedvehicle,Lu’ukai,2.)determiningtheR/VKiloMoana’sselfnoiseandcomparingittopreviouslycollecteddata,and3.)testingofthedepthaccuracyandswathcapabilityoftheKiloMoana’sKongsbergEM122multibeamechosounder.Unfortunately,alloftheaboveactivitiesrequiredseparateschedulingofshiptimeduetoduetodifferentmissionprofiles.Forinstance,theROVtestingrequiredtheuseoftheship’sbowthruster(thuscreatingaverynoisyandstationaryenvironmentunsuitableformultibeamtesting),whilethemultibeamcouldnotbetransmittingduringvesselnoisetesting(whichreliesupontheBuilt-InSystemTestingcapabilityoftheEM122).Finally,theEM122depthaccuracyandswathcapabilitytestingnaturallyrequiredtheshiptomoveovertheseafloorwhilepinging.Becauseofthis,ROVoperations(notdiscussedinthisreport)wereconductedduringdaylighthoursandtheacousticnoiseassessmentandthemultibeamtestingwereconductedatnight.InitialtestingduringKM1514werefocusedonquantifyingtheKiloMoana’sacousticselfnoisesignature.ThetestingprocessandresultsarewelldocumentedintheGatesreport.Inbrief,afterrigoroustestingofmultiplemodesofoperationitwasrevealedthatonechannelonthepre-amplifierboardwascausinganincreaseinnoiseacrosstheentirearray.MarkRognstad,oftheUniversityofHawaii,wasabletodisablethissinglechannelandtherebylowertheapparentreceivednoiselevelsdowntolevelssimilartothoseobservedin2012.However,furthertestingandinspectionofthemultibeamsonardatarevealedthat,despitethereductionintheapparentship’sacoustic/electrical

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noiselevels,thequalityofthemultibeambathymetrydatawasstillcompromised.Aftermultipleroundsoffurthersystemschecks,includingboardswaps,powersupplyswaps,andfranklyalotofheadscratchingbytheentireteampresent,itwasdiscoveredthatthequalityoftheswathdatawasimprovedsignificantlywhentheRXarraywasswitchedfroma2°toa4°RXbeamwidthconfiguration.ThisswitchismadeusingKongsbergsoftwaretoutilizehalfofthearrayforreceiverbeamformingprocess.Thisdiscoveryinducedfurthertesting,includingpullingtheRXcablesleadingfromtheRXmoduletothepre-amplifiersothatthesystemcouldutilizeonly4ofthe8RXarraymodulesatatime(makingita4°systematthehardwarelevel,ratherthanthroughthesoftware).Thismodificationyieldedthesameresultsasthesoftwaretest,sotheteamthencycledthroughdifferentgroupingsofRXmodulesbyadvancingdownthearray1moduleatatime.Thesetestsrevealedthatthe6thmoduleintheRXarray,whichhadbeenswappedinthespring2015shipyardperiodbyKongsbergduetohistoricallyhighernoiselevels,wasactuallywiredwithreversephase.Amazingly,awiringdiagramfortheRXmodulecablewasdiscoverednearthePre-Amplifierboxontheshipandajumperwasconstructedtocorrectthewiringandthereforeimprovethequalityoftheswathdata.Withcompletionofengineeringtroubleshooting,thefinalmodesofacousticnoisetestingwereperformedtocheckforanyresidualnoisewiththefullyfunctionalarray.Followingthis,theshipwasgivenovertotheQualityAssuranceTeamforthefinalfewhoursoftheKM1514legforaquickrunonthedeepwaterreferencesurfacearea,beforetheshiphadtotransitbacktoHonoluluHarbor.

EM122AccuracyTesting

Figure2.Thedeepwaterreferencesitecollectedduringthe2012EM122ShipboardAcceptanceTest.Referencesurfacedata

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weregriddedat100meters.ThecoloredEM122surface,shownhere,isoverlainonbackgroundbathymetry(SOESTMainHawaiianIslandMultibeamSynthesis)griddedat50m.

OverviewAccuracytestingwasconductedfortheEM122overadeepwaterreferencesurfacewithnominaldepthsof4700meters(Figure2).Thisreferencesurfacewasconstructedusingdatacollectedduring2012EM122ShipboardAcceptanceTestontheR/VKiloMoana.AllsoundingsinthereferencesurfacesandaccuracycrosslineswerecorrectedfortideusingtheOregonStateUniversityglobaltidemodel(http://volkov.oce.orst.edu/tides/otps.html).Furthermore,bathymetricslopeswerecomputedforthereferencesurfacesandusedasamasktoexcludeareasofsignificanttopography(>5°)fromthecrosslineanalysis(Figure3).Priortocollectionofthecrosslines,itwasverifiedthattheEM122wastheonlyacousticsystemrunningatthetime.

Figure3.Thedeepwaterreferencesitedatawithslopesover5°masked.Crosslineanalysiswasrunonthenorth-southorientedredlines.

ThecrosslinewasruninaNorth/Southdirection,butwassituatedtoavoidoverlappingnadirofthecrosslinewithnadirofthereferencesurfacelines.Thisprecautionwastakentoreduceanyeffectsofcompoundingorcancelingbiasesacrosstheswath.Toreducerefractionartifacts,anXBTprofilewascollectedpriortothestartofacquisitionofthecrossline,thenprocessedwithSVPEditor,andloadedintoSIS.Unfortunately,duetoengineissuesontheR/VKiloMoanacausingalarmsatslowerspeedsandincertainengineconfigurations,wehadtorunwithbothportandstarboardenginesrunning.Thisallowedaminimumspeedof8-9ktsinsteadofthedesiredspeedof6ktsrunningwithonlythestarboardenginesengaged;theslowerconfigurationwouldnormallybepreferredbecauseitisthequietestmodeofoperationsformultibeamcollectionandwouldincreasealongtracksoundingdensity.

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Majoroutliers(suchasbottomdetectionsatconstantrangeacrosstheswathduetointerference)wereremovedfromtheaccuracyanalysis,asthesewouldclearlybeeditedduringnormalbathymetricprocessing.Meandepthbiasanddepthbiasstandarddeviationsasapercentageofwaterdepthwerethencomputedin1°angularbinsacrosstheswath.

EM122AccuracyTestingResultsOnlyonecrossline(northandsouth)inonlyoneoperationmode(Table1)wasrunfortheEM122,astherewasverylimitedtimeavailablefortestingpriortodeparturefromthedeepwateraccuracysiteforport.Themeanbiasacrosstheswath(Figure4,bottom)isapproximatelyzero,withtheportsidevaluetrendingdeeperandthestarboardsidetrendingshallower,possiblyindicatingaslightrollbiasinthesystem.Thedepthstandarddeviation(Figure4,top)generallyshowsasimilarpatterntothatseenduringthe2012shipboardacceptancetest(Figure5,top)withouterportionsoftheswath(>45°)trendingfrom0.1to0.4%WD,withmostoftheinnerportionoftheswathfallingbelow0.1%WD.

Table1.EM122deepwateraccuracycrosslinesettings.

SONAR RUN TIME PARAMETERS Sector Coverage Cross Lines Settings 1 Max angle (port) 70 Max angle (sbtd) 70 Angular Coverage Mode Auto Beam Spacing HIDENS EQDIST Depth Settings Cross Lines Settings 1 Force Depth n/a Min depth (m) 4500 Max depth (m) 5000 Dual swath mode DYNAMINC Ping mode DEEP FM disable Unchecked (FM) Transmit Control Cross Lines Settings 1 Pitch stabilization ENABLED Along direction 0 Auto Tilt OFF Yaw stab. Mode REL. MEAN HDG heading n/a heading filter MEDIUM Min Swath Dist 0 Enable Scanning Off

Whatisalittletroublingwiththe2015dataisthatseveralregionsoftheinnerswathstandarddeviationexceed0.1%WD.In2012(Figure5,top),itcanbeseenthattheentireinnerportionoftheswathiscloseto0.05%WD,whiletheKM1514data(Figure4,top)plotshowsthattheinnerregionisnotnearlyasaccurate,withmultiplespikespresentandsomeexceeding0.1%WD.Potentialcomplicatingfactorsforthisassessmentarethehigherspeed(8+ktsin2015and6ktsin2012)andlessdesirableengineconfigurations(portandstarboardgeneratorsin2015versusstarboardonlyin2012)duringtheKM1514accuracydatacollection.Thisisapotentialdataqualityissuethatshouldbereevaluatedwhentimeis

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availablethroughadditionalpassesoverthereferencesurfaceindifferentengineconfigurations.

Figure4.EM122deepwateraccuracyresults(Deep,Dynamic,FM)fromKM1514.Top:depthbiasstandarddeviationasapercentageofwaterdepth.Bottom:meandepthbias(red)asapercentageofwaterdepth+/-onestandarddeviation(blue).

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Figure5EM122deepwateraccuracyresults(Deep,Dynamic,FM)fromthe2012R/VKiloMoanashipboardacceptancetest.Top:depthbiasstandarddeviationasapercentageofwaterdepth.Bottom:meandepthbias(solidmiddleline)asapercentageofwaterdepth+/-onestandarddeviation(dashedlines).

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EM122AchievedCoverage

Figure6.EM122accuracytestandtransitlinedatausedfortheswathcoverageassessment.Coloredbathymetryindicatesdatausedforswathcoverageassessment.

TheEM122swathcoverageperformancewasevaluatedbytrackingtheoutermostportandstarboardsoundingsfromalldataacquiredfromtheaccuracytestsiteandduringthetransittoHonoluluHarbor(Figure6).Figure7depictstheacross-trackcoverageversusdepthfordepthsbetween~300mand~4700m.Ideally,alldataincludedintheswathcoverageanalysisshouldhavebeencollectedinautomaticangularcoveragemode,automaticdepthmode,FMtransmitmode,at6ktsspeed,andperpendiculartotheslopeoftheseafloorinordertocalculatethemaximumswathwidthasafunctionofdepth.However,asmuchofthedatacoveringamajorityofthedepthrangewerecollectedduringthefinalhoursofthecruiseonatransitbacktoHonoluluHarbor,thespeedwashigherthandesired(8+kts)andtheshiptrackwasatanobliqueangletotheseafloorslopes.Thus,thedatacollectedmaynotfullyrepresentthemaximumswathwidthachievable.Aswathwidthof4timeswaterdepthwasobservedduringKM1514atthemaximumdepthmappedof~4700m(Figure7),whichisveryclosetothatseenduringthe2012SAT(Figure8).Inshallowerdepths,theKM1514dataseemstoshowsimilartrendsasthe2012SATforswathwidthasafunctionofdepth,withoverallswathwidthincreasingto5to6Xwaterdepthinshallowerwaters.Ideally,wewouldhavemoredatatobetterdefinethisswathcoveragecurve,butthelimiteddatafromKM1514suggestnomajorchangesinswathwidthperformancebetween2012and2015.

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Figure7.EM122coverageachievedduringKM1514.Datapointsaretheoutermostportandstarboardsoundingsfromeachping.Colorsofthepointsarebasedonthebackscatterstrengthsofthecontributingsoundings.

Figure8.Swathcoverageachievedduringthe2012SATconductedoversimilarsurveyareas.

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ConclusionsandRecommendations1. Havingthe“A”team(AcousticNoiseTeam,QualityAssuranceTeam,KongsbergMaritime,and

UHOceanTechnologyGroup)aboardtotroubleshoottheEM122multibeamproblemsworkedgreat.Withoutthismultidisciplinaryandtalentedgroup,itisprobablethattheissuemightnothavebeenresolvedwithoutadditionalshiptime.

2. TheEM122accuracyassessmentshowswhatappearstobealessaccurate/noisierinnerswaththanthatobservedin2012.Complicatingthisassessment,thetestswererunathigherspeedsandwithadifferentengineconfigurationcomparedto2012,duetothelimitedavailabletimeandengineissuesduringKM1514.Totrulycomparethetwoaccuracydatasets,additionalrunsshouldbeundertakenat6ktswithastarboardengineconfiguration.

3. Theassessmentofswathwidthasafunctionofdepthshowssimilarswathwidthatthereferencesurfacesite(~4700m)asseenin2012.ThetransitlinefromthereferencesitebacktoHonoluluHarborcrossestheseafloorslopesatobliqueanglesandwasrunathigherthandesiredspeedsduetotimeconstraints.Inlightofthesefactors,thereappeartobenomajorchangesinswathwidthfromthe2012SATtoKM1514.

4. Itwasnoticedthatthereweremanynadir“punch-through”artifactsseenduringthetransitbacktoHonoluluHarbor.Thiswasaverylimitedsamplinginterval,andtherewasnoattempttosteerthebeamsinordertoseeifthiscouldbeminimized.AmappingcruiseiscurrentlyunderwayandtheMACwillbecontactwiththescientistsaboardtoseeifthishasbeenanissue.