
SimradMS70
Coordinatesystems
Theheadingofthetransducerarrayismeasuredastheheadingoftheprojectionofaline
throughthefaceindexmarksintothehorizontalplaneofthevesselcoordinatesystem.If
thearrayismountedinsuchawaythattheX-axisisvertical,theheadinganglemustbe
measuredastheheadingoftheY -axiswith90°subtracted.Seethedenitionbelow.
Themeasurementofrollandpitchisdoneinacoordinatesystemwhichisthe
vesselcoordinatesystemrotatedabouttheZ-axissothatitsX-axisispointinginthe
transducer’sheadingdirection.
•Thepitchofthetransducerarrayismeasuredastheangleintheverticalplanebetween
thehorizontalplaneandthelinethroughtheindexmark.
ThepitchinstallationangleismeasuredbetweentheXaxisandthehorizontalplane.
Theangleispositiveiftheaxispointsupwards,andnegativeifitpointsdown.The
rangeisbetween-90°and+90°.
•Therollofthetransducerarrayismeasuredastheangleintheverticalplanebetween
thehorizontalplaneandalineonthefaceatrightangletothelinethroughtheindex
mark.
TherollinstallationangleismeasuredbetweentheYaxisandthehorizontalplane.
Theangleispositiveiftheaxispointsdownwards,andnegativeifitpointsup.The
rangeisbetween-180°and+180°.
Todetermineiftherollinstallationangleislargerthan+90°orsmallerthan-90°,
considerhowmuchrollwasrequiredtobringthetransducerarrayintoitsnalposition.
Usethestandarddenitionforrolldirection.
TheMS70softwareconvertsthemeasuredrollangletoarotationangle.Thisismade
withanarcsinecalculation,anderroneousmeasurementsordataentrymaymakethis
impossible.However,ifthemeasurementsaredoneaccurately,thiswillneverbea
problem.
Makingthemeasurements
Theactualmeasurementoftheinstallationanglesmaybedonebytwodifferentmethods:
1Themostaccuratemethodistouselandsurveyingtechniques,establishahorizontal
plane,anddodistancemeasurementstoandinthisplane.
2Thesecondmethodistouseaninclinometertomeasurerollandpitchangles
combinedwithdistancemeasurementsinthehorizontalplaneforheading.This
methodiseasier,butitrequiresasufcientlyaccurateinclinometer.
Whichmethodistobeusedmustbedeterminedbythefacilitiesavailable.Theuseof
landsurveyingtechniquesistherecommendedmethod,andisespeciallyappropriateon
anewvesselwhereallsensorlocationsmustbemeasured.Thetwoothermethodsmay
beappropriatewheninstallinganMS70onasurveyvesselwhereothersensorpositions
andorientationsarealreadyestablished.Aprerequisiteforusinganinclinometerisof
coursethatitisaccurateenough.
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