原模板挑选整理

DiscoveringPopularRoutesfromTrajectories,从轨迹中发现热门路线,分享人：亮亮图文,School&Author,School&Author,Theaim,DiscoveringtheMostPopularRoutebetweentwolocationsbyobservingbehaviorsofmanyprevioususers.,通过观察之前用户的行为，找出两地之间最热门的路线,Whydothis,Howdothis,Howdothis,Threesteps:,Howdothis,Threesteps:,Howdothis,Threesteps:,RelatedWork,Step1,MiningTransferNetwork,MiningTransferNetwork,Noticethatifthereisaroadmapavailable,wecanfindoutthetransfernetworkbymap-matchingtrajectories.,MiningTransferNetwork,Detecttheintersectionsoftrajectories,Intersectionsoftrajectories,Withinanintersectionregion,thedensityoftrajectorypointsisnormallyhigher,incomparisonwiththedensityofpointsonanincoming/outgoingroadedge,becauseitistheplacewheretrajectoriesjointogetherordriversslowdowntomakeaturn.Ifweconsideranintersectionasagroupofpoints,thenthesizeofthegroupshouldbegreaterthansomethreshold.,Intersectionsoftrajectories,Anumberoftrajectorieschangemovingdirectionatanintersection,assomepeoplemaketurns.Themovingdirectionsoftrajectorypointsfrom/todifferentroadedgesarelikelytobeorthogonal(i.e.,angleofdifferencetendsto/2).Withinasmalldistance,pointswhosemovingdirectionsdifferby0or(i.e.,inthesameoroppositedirection)areprobablyonthesameroad,whilepointswithdirectiondifference0andarepossiblymovingtodifferentroadbranchesofanintersection.Theclosertheangleofdifferencetendsto/2,thehigherpossibilitythatanintersectionexists.,Intersectionsoftrajectories,density,密度条件,direction,方向条件,Definition1,Definition1：Coherence,(,)istheEuclideandistancebetweenand,istheangleofdifferencebetweenandsmovingdirections,Definition2,3,Definition2：DirectlyCoherence-Connected,Definition3：Coherence-Connected,Ifthereisachainofpoints,and,Obviously,CoherenceConnectedisasymmetricandtransitiverelation.,Algorithm,Density,Coherence,Algorithm,Algorithm,Practice,Inpractice,asGPSdataismoreorlessdirty,wefirstreduceoutlierpointsthatsuddenlyjumpawaybyconsideringphysicallimitsonvehiclespeed,beforerunningtheclusteringalgorithm.Besides,linearinterpolationisconductedforlowsampling-ratetrajectoriestoreducethepossibilitythattheyaremissedatsomeintersectionsthattheydopassthrough.DirectionsmoothingisalsocarriedouttoalleviatetheeffectofpositionfluctuationcausedbyGPSinaccuracy.,MiningTransferNetwork,Afterdiscoveringalltheclusters(intersections),wetreateachofthemasatransfernodewhoselocationisapproximatedbytheaveragecoordinate,whiletransferedgesareconstructedbycheckingtrajectoriesbetweennodes.,Step2,DerivingTransferProbability,Theaim：,DerivingTransferProbability,Where(,)istheshortestEuclidean/networkdistancebetweenandthefrontpartofthatstartsfrom.,RandomWalk,Ifweconductsucharandomwalk,whatistheexactprobabilitythat,startingfromanode,wewilleventuallyreachthedestinationwithinsteps?,用t步从ni走到nj的概率,在t步之内步从ni走到nj的概率,Chooseparameterc,Setasthediameterofthetransfernetworkinourexperiments,whichguaranteesatleastoneroutecanbefoundbetweenanytwonodesandalsoavoidsconsideringthoseexcessivelylongroutes.,AMCM,AbsorbingMarkovChainModel:,Astate(node)ofaMarkovchainiscalledabsorbingifitsimpossibletoleaveit.,AMCM,AMCM,Assumetherearetotallyabsorbingstates,andtransientstates(+=).WegroupabsorbingstatesintoABSandtransientstatesintoTR.,Transfermatrix：,Howtocalculate,Example：,P=,2=?,213=?,1/3+1/4=7/12,Whydothis,Lemma3:,Whydothis,在t步之内步从ni走到d的概率,用t步从ni走到d的概率,Whydothis,Expressedinmatrixform:,Howtocalculate1,Howtocalculate2,D=,=,S,D,y-by-x,x-by-1,y-by-1,Howtocalculate3,D=,=,Q,QD,y-by-y,y-by-1,y-by-1,D,Step3,SearchingTheMPR,热门程度的另一表达形式:,路线热门程度定义:,Algorithm,Algorithm,(),Why,However,aproblemwiththisalternativeoptionisthatthesearchalgorithmjustconsidersthelocalinformationofthecurrentnodeotherthanstepsfurther,whichpossiblycausesanincorrectresult.,author,Experiments,Contributions,Wepresentanewrouteplanningapproachthatgivesanotheroptionforusersotherthanexistingshortestpathbasedmethods.,Wedevelopanalgorithmtoestablishthetransfernetworkmodelofacollectionofhistoricaltrajectories,andutilize