简介:Dynamiccharacisticsoflargestructures,suchastallbuildings,long_spansuspension,cable_stayedbridgesandtallchimneys,includingrelativedisplacementsandvibratingfrequencies,arekeytoassesstheirdriftandstressconditions,Thesestr_ucturesaredifficulttomeasuredirectly,especiallyundertheconditionofearthquakesorstrongwind/typhoon.Ingeneral,accelerometersarethemostcommoninstrumentsusedtomonitortheresponseofstructuralsystems,butdisplacementmeasuringrequiresprocessingbydoubleintegration.Theintegrationprocesscannotbeautomatedbecauseofthefollowingrequirementsofsignalprocessing:(a)choiceoffiltersandbaselinecorrection(theconstantsofintegration),and(b)substantialjudgmentswhenanomaliesexistintherecords.Consequently,thisprocesscanleadtoerrorsinthecalculationofvelocitiesanddisplacements,someasurementswithaccelerometercannotbeusedtodiscoverdisplacementsatthecentimeterlevelinreal_timeornearreal_time.Othertraditionalmethods,likelasercollimatorandtotalstation,canbealsoappliedtomeasuredisplacementsatveryhighprecision,butcannotworkproperlyduringearthquakesorstrongwinds/typhoons,andinmostcasesdonotworkinreal_timeornearreal_time.Untilrecently,therearenoefficientorfeasiblemethodstomeasuredisplacementsduringanearthquakeorseverewind.Therefore,thereisagreatneedfordevelopinganewmethodortechniquetomonitorthedynamiccharacteristicsoflargestructurespreciselyinreal_timeornearreal_timeunderbadconditions. Fortunately,recentadvancesinGlobalPositioningSystem(GPS)technologyenableabove_mentionedlong_periodchangesofstructurestobereliablymonitored.GPSreceiverswithacapabilityofresolvingmotionatthecentimeterorsub_centimeterlevelandsamplingfrequency10Hzoreven20Hzarenowavailablefromseveralmanufacturers.Thatprovidesagreatopportunitytomonitorlong_periodchangesofstructuresreliably,andwillbeveryusefulfors
简介:摘要GPS测量技术的出现和发展,给工程测绘工作带来了极大的便利,改变了传统测绘工作方式,大大提高了工程测绘的工作效率和增加了工程测绘的服务项目。本文主要从GPS测绘技术的含义、特点等方面来探讨GPS测量技术在工程测绘中的应用。
简介:在动力学轨道拟合以及轨道积分的基础上,提出了基于IGS精密星历的GPS卫星轨道预报方法。该方法首先利用已知的IGS精密星历作为虚拟观测值,采用动力学方法拟合出GPS卫星的初始轨道和动力学参数,然后再通过积分来预报GPS卫星的轨道。主要讨论了基于不同弧段的IGS星历时,该方法对GPS卫星轨道的拟合和预报情况。研究结果显示:对于6d弧段以内的IGS精密星历,其拟合轨道与IGS精密星历差值的三维RMS值均优于4cm,随着拟合弧段的增加,拟合残差变大;当利用2~6d弧段的IGS星历来预报GPS轨道时,大部分卫星第1天、第7天和第30天的三维预报精度可优于0.1m、3m和100m。其中,2d弧段的IGS星历对GPS卫星第1天和第7天的预报结果最好,5d弧段的IGS星历对GPS卫星第30天的预报结果最好。
简介:Thispaperusesmulti-quadricequationsinterpolationtoes-tablishawidelycoveredandvaluablespeedfieldmodelofChina,withwhichthehorizontalcrustalmovementpatternsareobtained.Thepresent-dayverticalcrustalmovementvelocityim-ageofChinaisalsoexpressedbyGPSobservations,fromwhichwecanknowtheverticalcrustalmovementpatterns.