LEVELINGCaltransLEVELNG加州运输局

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1、UNIT6LEVELINGBillJackson,PLSCarrolLeong,PLSCaliforniaDepartmentofWaterResourcesIntroduction“Leveling”isageneraltermusedinlandsurveyingthatappliestoverticalmeasurements.Verticalmeasurementsaremadeandreferencedtodatums,aselevations.Thereferencedatummightbeanarbi

2、traryelevationchosenforconvenienceoraveryprecisevaluedeterminedafterlengthystudies.ThestandardreferencedatumusedthroughoutCaliforniaismeansealevel,basedontheNationalGeodeticVerticalDatum(NGVD1929).Threemethodsusedtomeasuredifferencesinelevationaredirectvertica

3、lmeasurement,trigonometricleveling,anddifferentialleveling.Itisimportanttounderstandtheprocedure,equipmentandnotekeepingformatusedforeachmethod.CaltransLS/LSITVideoExamPreparationCoursePerformanceExpectedontheExamsDefinetheterms“curvature”and“refraction,”beabl

4、etocalculatetheircombinedeffectsandexplaintheprocedureusedtolimittheireffects.Explainhowtopegalevelandcalculatethecollimationcorrectionofaproperlyadjustedlevel.Givenfieldmeasurements,calculatethedifferenceinelevationbetweentwostationsusingtrigonometricleveling

5、method.Explain,interpret,reduceandadjustdifferentiallevelingnotes.Explain,interpret,reduceandadjustthree-wirelevelingnotes.Obtainthedifferenceinelevationbetweentwostationsbyreciprocalleveling.PlanandanalyzetheresultsofalevelingprojectwithregardtoNGSstandardsan

6、dspecifications.KeyTermsAltimetryLenkerrodAutomaticpendulumlevelMeansealevelBacksight(+shot)NationalGeodeticVerticaldatum(NGVD1929)BenchmarkNorthAmericanVerticalDatumCurvature(NAVD1988)DatumPeggingalevelDirectlevelingPhiladelphiarodDifferentiallevelingPlumblin

7、eElevationProfilelevelingForesight(-shot)ReciprocallevelingH.I.RefractionHorizontallineThree-wirelevelingHorizontalplaneTrigonometriclevelingIntermediateforesight(sideshot)Turningpoint(TP)LevelingVerticaldifferenceLevelsurfaceVerticallineLevelline6-2LevelingVi

8、deoPresentationOutlineBasicConceptsEarth'sSurface90˚1HorizontalLineElevationBenchmarkLevelLines2ElevationDatumVerticalLinesFigure6-1.Levelingconcepts.•Levelline•Horizontalline•Vert