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Extracted Abstract:
—Massivetaxitrajectorydataisexploitedforknowledgediscoveryintransportationandurbanplanning.Existingtools typicallyrequireuserstoselectandbrushgeospatialregionsonamapwhenretrievingandexploringtaxitrajectoriesandpassenger trips.Toanswerseeminglysimplequestionssuchas“WhatwerethetaxitripsstartingfromMainStreetandendingatWallStreet inthemorning?”or“WherearethetaxisarrivingattheArtMuseumatnoontypicallycomingfrom?”,tediousandtimeconsuming interactionsareusuallyneededsincethenumericGPSpointsoftrajectoriesarenotdirectlylinkedtothekeywordssuchas“Main Street”,“WallStreet”,and“ArtMuseum”.Inthispaper,wepresentSemanticTraj,anewmethodformanagingandvisualizingtaxi trajectorydatainanintuitive,semanticrich,andefficientmeans.WithSemanticTraj,domainandpublicuserscanfindanswersto theaforementionedquestionseasilythroughdirectqueriesbasedontheterms.Theycanalsointeractivelyexploretheretrieveddata invisualizationsenhancedbysemanticinformationofthetrajectoriesandtrips.Inparticular,taxitrajectoriesareconvertedintotaxi documentsthroughatextualizationtransformationprocess.ThisprocessmapsGPSpointsintoaseriesofstreet/POInamesand pick-up/drop-offlocations.Italsoconvertsvehiclespeedsintouser-defineddescriptiveterms.Then,acorpusoftaxidocuments isformedandindexedtoenableflexiblesemanticqueriesoveratextsearchengine.Semanticlabelsandmeta-summariesofthe resultsareintegratedwithasetofvisualizationsinaSemanticTrajprototype,whichhelpsusersstudytaxitrajectoriesquicklyand easily.Asetofusagescenariosarepresentedtoshowtheusabilityofthesystem.Wealsocollectedfeedbackfromdomainexperts andconductedapreliminaryuserstudytoevaluatethevisualsystem. IndexTerms —TaxiTrajectories,TaxiDocument,Textualization,NameQuery,SemanticInteraction,TextSearchEngine 1