Visualiza(on, Selec(on, and Analysis of Traffic Flows RoelandScheepens,ChristopheHurter,HuubvandeWetering,andJarkeJ.vanWijkIEEETransac@onsonVisualiza@onandComputerGraphics,Vol22,No1,January2016

Presenta@onbyAlistairWick

Overview

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Mo(va(on

•  Individualsmove,butgroupsmaketraffic•  Trafficisunpredictable,butnotrandom–itformspaPerns•  ThesepaPernsareimportant,butdifficulttoanalyse

•  ThistoolhelpsusexaminethesepaPerns,andhowtheychange•  Takesanovelapproach,usinganima@onasakeyvisualchannel

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Data

•  Trajectoriesover@me

10softhousandsofjourneys 100softhousandsofsamplepoints4

Data CaseStudies• OnedayoverParis:17,841flights,424,546samples• VesseldatanearDutchcoast:16,421vessels,420,335samples

10softhousandsofjourneys 100softhousandsofsamplepoints5

Data

•  Largenumbersofoverlappingtrajectories• Highdensityvaria@on• Ataminimum,dataincludes:•  Posi@on•  Heading•  Velocity

• Mayalsoinclude:•  Vehicletype•  Al@tudeforaircra^

• Approachisdesignedfororderedtraffic,notrandommovements!

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Approach • Densitymapshowswherethetrajectorieslie•  Likeahigh-resolu@onheatmap,simplelightnessencoding•  High-leveloverviewofthepathstaken

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Approach • Animatedpar@cleflowshowsdirec@on•  LowcluPer(unlikeglyphs,arrows)•  Leavesawiderangeofvisualchannelsforotheruses

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Approach

•  Importanttorealisethepar@clesarenotmarkingindividualvehicles•  Theyareavisualaidtoshowdirec@onofflow• Notpartofthedata:vislayeraddedbytheapplica@on

• Usessomeformofedgebundling(maybeop@onal)ontrajectories

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Alterna(ves

• Animatedtextures•  Doesn’tworkforthintrajectories

• Colormaps•  Lowresolu@on,can’toverlap

• Arrows/Glyphs•  CluPered;obscuretheview

• Couldjustshowthevehicleloca@ons?•  Terribleforiden@fyingdis@ncttrajectories

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Par(cle Display Method

Incorporatedtodensitymap• Hardtocombinewithcolor•  Imprecise

GaussianBells• Alpha-blendedontopofmap•  Easytocolor• Highvisibility

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Par(cle Flow - Pros

• Canresolveopposingdirec@ons•  LowcluPer•  Intui@ve;mo@onencodesmo@on•  Low-prioritychannel–colorchannelsremainfree

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Par(cle Flow - Cons

•  (Very)highoverhead• Requiresguaranteedperformance• Real-@merenderingathighresolu@onandframerate•  Thousandsormillionsofpar@cleswithconstantturnover

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Par(cle Flow - Cons

•  (Very)highoverhead• Requiresguaranteedperformance• Real-@merenderingathighresolu@onandframerate•  Thousandsormillionsofpar@cleswithconstantturnover

*Challenging–butnotintractable

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Selec(on/Filtering

• Bothrepresenta@onsrespondtoselec@on•  Thisishowtheuserexploresthedata•  Selec@onsarelocalizedandfilterallpathspassingthroughthem:

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Selec(on/Filtering

•  Selec@onsarealsodirec.onal•  Theuserpicksadirec@onrangetofilter–pathswhichmatchtherangewithintheselec@onareaareselected

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The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.

•  Selec@onscanberefinedinotherdimensions• Here,theuserfiltersbyal@tude:

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Selec(on/Filtering

• Differentmodesofselec@oncanbecombined• Compoundselec@onsuseset-likelogic:

• Where⊕canbeeither⋃or⋂(unionorintersec@on),and∖issetsubtrac@on

•  Extremelypowerful• Usercanadd,intersect,andsubtract(inverse)selec@ons

𝑆=⊕ 𝑆↓𝑖 ∖⋃ 𝑅↓𝑖 

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Selec(on/Filtering

Summary:• Polygonalselec@onareas•  Selectstrajectoriespassingthrougharea

•  Selectforheading/al@tuderanges•  Customselec@onwidget

• Powerfulcompoundselec@ons• Usercanenable/disablespecificselec@ons• Canhidetheunselectedtrajectories• Parametric–selec@onscanbemodifiedatany@me

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Examina(on

• Detailwindowscanbedisplayedon-demandforanyselec@on

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Fig.6(page6)

Examina(on

•  Zoomedviewofselec@onarea• Histogramoftrajectoriesover@me•  Polarareahistogramofdirec@ons•  Allsub-plotsarelinked•  Pickableselec@oncolor

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Comparison

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• Differentwindowsarealsolinked

Comparison

• Windowscanbecombinedformoredirectcomparison

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Use-Case: Infographics

• Mul@pleselec@onscreateafacetedviewsuitableforinfographics• Hereasta@cviewcontainsalltheinforma@onneeded

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Fig.10(page8)

Use-Case: Infographics

• BoattrafficontheDutchcoast• Antwerp(boPom)histogramshowswavepaPern–@descominginandout!

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Fig.11(page9)

Use-Case: Air Traffic

•  FlightsinandoutofCharlesdeGaulleairport•  Take-offinblue•  Landingingreen• Partofevalua@onwith2professionalflightcontrollers

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Fig.9(page8)

Use-Case: Air Traffic

•  Sameviewrotatedtoshowal@tude• Alterna@ngincoming/outgoingflows• Differentflowscanbeselectedandcompared

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Fig.9(page8)

Thanks! Ques(ons?

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