I.#Introduction · 5# Introduction,#Overview# From digital mapping to mobile social networking –...

Mobility(Data((Management(&(Exploration(

(I.#Introduction#

Yannis&Theodoridis&&&Nikos&Pelekis&InfoLab(|(University(of(Piraeus(|(Greece((

infolab.cs.unipi.gr((

(

2013.08(

2#

“Τα πάντα ρει, µηδέποτε κατά τ’ αυτό µένειν – Everything changes, nothing remains still”

Heraclitus (500 BC)

3#

Acknowledgments#

!  The(content(of(this(lecture(series(has(been(inspired(

by(collaboraBve(work(done(in(the(following(EU(

projects:((

"  FP7/SEEK((hNp://www.seekOproject.eu),(2012O15(

"  FP7/DATASIM((hNp://www.datasimOfp7.eu),(2011O14(

"  ESF/COSTOMOVE((hNp://moveOcost.info),(2009O13(

"  FP7/MODAP((hNp://www.modap.org),(2009O12(

"  FP6/GeoPKDD((hNp://www.geopkdd.eu),(2005O09(

!  Also,(special(thanks(to(InfoLab(members(

GeoPKDD Geographic Privacy-aware Knowl. Discovery & Delivery

4#

Previous#versions#of#this#material#

"  2013(

!  PhDOlevel(seminar(@(JRC,(IsrpaOItaly,(Apr.(2013(

"  2012(

!  PhDOlevel(seminar(@(Univ.(Cyprus,(Nov.(2012(

!  MSc(course(@(KAUST,(Jeddah,(Saudi(Arabia,(Jun.(2012(

!  PhD(course(@(Univ.(Ghent,(Belgium,(Feb.(2012(

"  2011(

!  PhD(course(@(Univ.(Trento,(Italy,(Nov.(2011(

!  PhD(course(@(Univ.(Aalborg,(Denmark,(Sep.(2011(

!  MSc(course(@(KAUST,(Jeddah,(Saudi(Arabia,(Jun.(2011(

!  PhD(course(@(Univ.(Milano,(Italy,(May(2011(

"  2010(

!  PhD(course(@(Univ.(Venice,(Italy,(Jun.(2010(

More(details(at:(hNp://infolab.cs.unipi.gr/((

5#

Introduction,#Overview#

From digital mapping to mobile social networking – A tour on geospatial information management

challenges

6#

Mobile#devices#and#services#

!  Large(diffusion(of(mobile(devices,(mobile(services(and(locaBonObased(

services(#(loca3on4&and&mobility4aware&data&

7#

Which#data?#

!  LocaBon(data(from(mobile(phones((

"  i.e.,(cell(posiBons(in(the(GSM/UMTS(network(

!  LocaBon((and(trajectory)(data(from(GPSOequipped(devices(

"  Humans((pedestrians,(drivers)(with(GPSOequipped(smartphones(

"  Vessels(with(AIS(transmiNers((due(to(mariBme(regulaBons()(

!  LocaBon(data(from(indoor(posisBoning(systems(

"  RFIDs((radioOfrequency(ids)((

"  WiOFi(access(points(

"  Bluetooth(sensors(

8#

GPS#Data#

!  Raw(data:(GPS(recordings(

objectID, trajectoryID, timestamp, longitude, latitude

201100024,1,2009-01-02 08:54:07,24.609728324369,38.013503319816

201100024,1,2009-01-02 08:54:25,24.6094016577037,38.0127699864845

201100024,1,2009-01-02 08:55:06,24.6086749910399,38.011116653155

201100024,1,2009-01-02 08:55:56,24.6076299910435,38.0092066531597

201100024,1,2009-01-02 08:56:16,24.6071983243782,38.0084733198281

201100034,1,2009-01-02 04:19:26,23.1092366579214,38.5853616531322

201100034,1,2009-01-02 04:19:36,22.9272199909328,38.8922416526431

201100034,1,2009-01-02 04:19:45,23.0359933243564,38.7788549861265

201100034,1,2009-01-02 04:19:55,22.9355449909622,38.868204986019

201100034,1,2009-01-02 04:20:05,23.0638616578755,38.6383849863914

...

9#

GPS#Data#

"  Q:(where(is((24.6071983243782,(38.0084733198281)(located(?(

"  A:(in(the(short(sea(passage(between(Euboea(and(Andros(islands,(

Greece(

What#is#a#(GPSKbased)#trajectory?#

!  A(trajectory(is(a(model(for(a(moBon(path(of(a(moving(object(

(human,(animal,(robot,(…)(

"  (due(to(discreBzaBon)(a(sequence(of(sampled(BmeOstamped(locaBons(

(pi,(t

i)(where(p

i(is(a(2D(point((x

i,(y

i)(and(t

i(is(the(recording(Bmestamp(of(p

i((

10#

What#is#a#(GPSKbased)#trajectory?#

!  A(common(representaBon(in(MOD(is(a(3D&polyline&where(verBces(correspond(to(BmeOstamped(locaBons((p

i,(t

i)((

"  Usually,(linear&interpola3on(is(assumed(between((pi,(t

i)(and((p

i+1,(t

i+1)(

(pi,ti) (pi+1,ti+1)

11#

From#“raw”#to#“semantic”#trajectories#

12#

•  Semantic Trajectory: T={efirst,…,elast}

•  Episode: ei = (STOP | MOVE, tfrom, tto, place, tag)

raw&mobility&data&&sequence&(x,y,t)&points&

e.g.,&GPS&feeds&&

meaningful&mobility&tuples& <place,&3mein,&3meout,&tags>&

Home (breakfast) office (work) Market (shopping) Home (relax)

Road (bus)

Train (metro)

Sideway (walk)

[~, 8am]

[8am, 9am] [6pm, 6:30am] [7:30pm, 8pm]

[9am, 6pm] [6:30pm, 7:30pm] [8pm,~]

13#

Examples#of#GPS#trajectory#data#

!  “Amki”(dataset:(vehicles(moving(in(Athens(metropolitan(area(

"  ~1.5(million(GPS(recordings(#(~4,500(trajectories(

14#

Examples#of#GPS#trajectory#data#

!  “IMIS3days”(dataset:(vessels(sailing(in(Mediterranean(sea(

"  (only(a(small(subset(of(the(dataset(at(hand)((

~3(million(GPS(recordings(from(933(vessels(during(a(3(days(period(#(

1500(trajectories(

15#

Background#on##Positioning#technologies#

16#

GeoKpositioning#

!  PosiBoning(technologies((all(standardized(in(early(2000’s)(

"  Using(the(mobile(telephone(network(

!  Time(of(Arrival((TOA),(UpLink(TOA((ULOTOA)(

"  Using(informaBon(from(satellites(

!  Global(PosiBoning(System((GPS);(Assisted((AOGPS);(DifferenBal(GPS((DOGPS)(

source: ESA

17#

SatelliteKsupported#positioning#

!  GPS((Global(PosiBoning(System)(

"  Fully(operaBonal(since(1994(

"  24Osatellite(constellaBon(

!  monitored(by(5(monitoring(staBons(and(4(ground(antennas;(handled(with(

(extremely(precise)(atomic(clocks(

!  At(least(5(satellites(are(in(view(from(every(point(on(the(globe(

"  GPS(receiver(gathers(informaBon(from(4((

(or(3,(the(minimum)(satellites(and((

(a)(triangulates(to(posiBon(itself;((

(b)(fixes(its((nonOatomic)(clock(

"  PosiBon(accuracy:(~20m(

18#

GeoKpositioning#(cont.)#

!  GPS(accuracy(improvements(

"  Assisted&GPS&(A4GPS):(provides(preOcalculated(satellite(orbits(to(the(receiver;(accuracy(~10m(

"  Differen3al&GPS&(D4GPS):(combines(with(land((antennas)(informaBon;(

accuracy(down(to(1m(

19#

GeoKpositioning#(cont.)#

!  GPS(compeBtors(

"  Glonass((Russia)(–(currently,(semiOoperaBonal((

!  24Osatellite(constellaBon;(1O10m(accuracy(

"  Galileo((EU)(O(fully(operaBonal(by(2019(

!  30Osatellite(constellaBon;(1m(accuracy(

"  Beidou((China)(O(fully(operaBonal(by(2020(

!  35Osatellite(constellaBon;(10m(accuracy(

20#

LocationK#and#MobileKaware#Applications#...#

21#

DeYinitions#

!  (source:(Swedberg,(1999)(Mobile&Loca3on&System&(MLS)&is(a(locaBon(system,(including(applicaBons,(that((

"  determines(the(geographic(posiBon(of(mobile(subscribers(and((

"  provides(them(with(relevant(informaBon(and(services(

!  (source:(Wikipedia)(A(Loca3on4Based&Service&(LBS)&in(a(cellular(telephone(network(is(a(service(provided(to(the(subscriber(based(on(

her(current(geographic(locaBon(

22#

LocationKbased#Services#&#Tools#

!  NavigaBon((vehicle(or(pedestrian)(&(InformaBon(services(

"  RouBng,(finding(the(nearest(pointOofOinterest((POI)(

"  LocaBonObased(yellow(pages((“whatOisOaround”,(…)(

!  Resource(management(&(Tracking(apps(

"  (taxi,(truck,(etc.)(fleet(management,(administraBon(of(container(goods,(

locaBonObased(charging(

"  Tracing(of(a(stolen(car,(locaBng(persons(in(an(emergency(situaBon,(…(

!  Social(networking(apps(

"  Google(LaBtude,(Facebook(places,(Foursquare,(etc.(

23#

LocationKbased#Services#&#Tools#(cont.)#

!  FindOtheONearest(

"  finds(the(nearest(point(of(interest((POI)(O(restaurant,(gas(staBon,(etc.((

(suggests(the(opBmal(way(to(move(there((Router)(

!  ‘opBmal’(in(terms(of(minimum(distance((driving(mode)((

or(minimum(Bme((walking(mode)(

!  EO911((US),(EO112((EU),(EO119((Japan)(emergency((

call(numbers(

"  mandates(require(locaBng(the(caller(within((

a(few(meters((150(feet,(by(FCC(regulaBon)(

"  (in(US)(EO911(call(centers(receive(15,000(calls(from(cellular(phones(per(

day(

24#


Google My Tracks Walktastic by runtastic

25#


RunKeeper

26#


!  Tracing(lost(or(stolen(products(

"  Lost(smartphones:(“Find(my(iPhone”,(“Where’s(my(Droid”(etc.(

"  Stolen(cars:(“Volvo(connecBvity”(

27#


!  (

(

See(in(real(Bme(where(your(friends((are!((launched(Feb.09(by(Google)(

28#


!  Google&places:(Rate(and(share(places(on(Google(

!  Google&places&for&business:((

"  (business(perspecBve)(Get(your(

business(found(on(Google(

"  (end(user’s(perspecBve)(rate(

products,(search(for(similar,(compare(

prices,(etc.(

29#


"  Tag(yourselves(and(find((

tagged(friends(

"  Tell(your(friends(where(you(are,((

suggest(places,(etc.(

30#

What#can#we#do#with#/#learn#from#mobility#data#...#

31#

Querying#with#vehicles#datasets…#

!  (global)(Traffic(monitoring(

"  How(many(cars(are(in(the(ring(of(the(town?(

"  Once(an(accident(is(discovered,(immediately(send(alarm(to(the(

nearest(police(and(ambulance(cars(

32#

Querying#with#vehicles#datasets…#

!  (personalized)(LocaBonOaware(queries(

"  Where(is(my(nearest(Gas(staBon?(

"  What(are(the(fast(food(restaurants(within(3(miles(from(my(locaBon?(

"  Let(me(know(if(I(am(near(to(a(restaurant(while(any(of(my(friends(are(

there(

33#

Querying#with#vessels#datasets…#

!  Querying(and(mining(trajectories:(

"  Extract(/(draw(the(ship(tracks((detailed(vs.(simplified)((

"  Calculate(average(and(minimum(distance(from(shore;(where(and(when((

"  Calculate(the(number(of(ships(in(the(vicinity(of(the(ship((e.g.(10(n.m.(

radius)((

"  Find(whether((and(how(many(Bmes)(a(ship(goes(through(narrow(

passages(or(biodiversity(boxes((

"  Calculate(the(number(of(sharp(changes(in(direcBon(

"  Find(ships(following(typical(routes(vs.(outliers(

34#

Querying#with#vessels#datasets…#

ApplicaBonO(oriented(analysis:(

!  Improving(safety(

"  Analyze(the(accuracy(of(data(provided(by(base(staBons(

!  Traffic(opBmizaBon(

"  Calculate(metrics(from(the(traffic:(traffic(density,(mean(distance(between(ships,(

number(of(trajectories(that(are(close(to(the(‘opBmal’(departure(–(arrival(path(

"  Devise(new(sea(routes(to(handle(traffic(increase(

"  Measure(the(acBvity(of(each(ship:(number(of(intermediate(stops(

!  Environmental(consideraBons(

"  Compare(trajectories(with(environmental(consideraBons((fuel(consumpBon,(

noise(polluBon),(

35#

!  Examples(of(“mobility(paNerns”(

"  Hot4spots((popular(places)(([Giannom(et(al.(2007](

"  T4PaRerns(([Giannom(et(al.(2007](

"  Hot&mo3on&paths(([Sacharidis(et(al.(2008](

"  Typical&trajectories(([Lee(et(al.(2007](

"  Moving&clusters(([Kalnis(et(al.(2005](

"  Flocks&&&Leaders(([Benkert(et(al.(2008](

"  Convoys(([Jeung(et(al.(2008](

"  Centroid&trajectories(([Pelekis(et(al.(2009O10](

δt

ε

X

Y

T

T1 T2 T3

…#more#ambitious:##Patterns#over#trajectory#datasets#

36#

Back#to#LBS#discussion#

!  According(to((Gratsias(et(al.(2005;(Frentzos(et(al.(2007)(

Reference&object&&(user)&

&Database&&objects(

sta3onary( mobile(

sta3onary&⇒  whatOisOaround(⇒  rouBng(⇒  findOtheOnearest(

⇒ ((guideOme(

mobile& ⇒ (findOme( ⇒ (getOtogether(

Almost every current commercial app is classified as stationary-stationary !!

37#

Routing#

!  (“Get(DirecBons”(in(Google(maps)(

!  Find(the(opBmal(route(from(a(departure(to(a(desBnaBon(point((

"  Goal(to(be(opBmized:(the(minimal(network(distance(traveled(or(the(

minimal(traveled(Bme(or(…(

!  Relates(to(the(wellOknown((

shortest&path&(SP)&problem(from((

graph(theory(and(network(analysis(

"  Several(offOtheOshelf(soluBons,(e.g.((

Dijkstra’s(singleOstart(SP(algorithm(

Live example: Get from Uni. Piraeus to Acropolis Museum: http://g.co/maps/jvjvc

38#

Routing#(cont.)#

!  Relates(to(the(wellOknown(shortest(path((SP)(problem(from(graph(

theory(and(network(analysis(

"  Several(offOtheOshelf(soluBons,(e.g.(Dijkstra’s(singleOstart(SP(algorithm(

"  Example(of(Dijkstra’s(SP:((

“find(the(SP(from(A(to(D”(

39#

Routing#(cont.)#

40#

WhatKisKaround#

!  (“Search(nearby”(in(Google(maps)(

!  Retrieve(and(display(all(POI(located(in(the(surrounding(area(

(according(to(user’s(locaBon(or(an(arbitrary(point)(

"  Area(could(by(rectangular(or(circular(or(of(any(other(shape(

"  Example:(“Provide(me(all(the(gasOstaBons(and(ATMs(within(a(distance(

of(1km”(

"  It(is(as(simple(as(a(typical(range(query!(

!  Recall(the(slides(about(range(query(processing(using(ROtrees!(

Live example: Search for hotels around Acropolis museum: http://g.co/maps/wzbaw

41#

WhatKisKaround#

42#

FindKtheKnearest#

(not(supported(by(Google(maps!)(

!  Retrieve(and(display(the(nearest(POI((restaurants,(museums,(etc.)(

with(respect(to(a(reference(locaBon((

"  Example:(“find(the(two(restaurants(that(are(closest(to(my(current(

locaBon”(or(“find(the(nearest(café(to(the(railway(staBon”(

"  Issue:(distances(are(computed(wrt.(the(network(rather(than(the(free(

space((Euclidean(distance)(

(

!  StateOofOtheOart(algorithm((at(the(spaBal(database(domain):(

"  “Euclidean&Restric3on”((Papadias(et(al.(2003)(

How about getting the 1-nearest hotel wrt. Acropolis museum?

43#

FindKtheKnearest#

Closest wrt. Euclidean distance Closest wrt. network distance

44#

FindKtheKnearest#(cont.)#

!  Euclidean(RestricBon(

"  1st&step:&Find&object&P1&which&is&nearest&to&Q&wrt&Euclidean&distance&&

"  2nd&step:&D1&is&the&network&distance&between&P1&and&Q&

45#

FindKtheKnearest#(cont.)#

!  Euclidean(restricBon(

"  3rd&step:&Retrieve&all&points&(Pi)&with&Euclidean&Distance&from&Q&less&than&D1&&

"  4th&step:&Among&all&Pi,&find&the&one&with&the&minimum&network&distance&from&Q&

46#

Advanced#LBS#

!  Examples(

!  Constrained&rou3ng&(advanced(wrt.(geometry(/(complexity)&

"  alternaBve(names:(inOroute(findOtheOnearest((Frentzos(et(al.(2007),(

tripOplanningOquery((Li(et(al.(2005)(

!  “Get4together”(or(“Find4me”((moBon(is(involved)&

"  See(also(Google(LaBtude,(etc.((

47#

Constrained#routing#

!  Find(the(opBmal(route(from(a(departure(to(a(desBnaBon(point(…(

"  …(with(the(extra(constraint(to(pass(through(one(among(a(specified(set(

of(candidate(points(

"  Example:(“provide(me(the(best(route(office(to(home(constrained(to(

pass(from(a(bank(ATM(”(

48#

Constrained#routing#

!  Any(idea(for(pruning?(

49#

Constrained#routing#(cont.)#

!  VariaBon(of(Euclidean(RestricBon(

"  1st&step:&Retrieve&the&op3mal&route&R&between&P&and&Q&

50#



"  2nd&step:&Retrieve&the&Euclidean&NN&w.r.t.&route&R&(point&N1)&

51#



"  3rd&step:&Calculate&network&distances&D1=Net_Dist(P,N1)&and&D2=Net_Dist(N1,Q)&

52#



"  4th&step:&Retrieve&all&candidate&objects&(Ni)&with&total&Euclidean&distance&from&both&P&and&Q&less&than&&D&=&D1&+&D2&

Perpendicular bisector

Circumference

53#



"  5th&step:&For&each&Ni,&calculate&D1i&=&Net_Dist(P,Ni)&and&D2i&=&Net_Dist(Ni,Q),&and&report&the&Ni&the&one&that&minimizes&Di&=&D1i&+&D2i&

54#

“GetKtogether”#(or#“Find#me”)#

!  A(number(of(moving(objects(try(to(meet(a(moving(object(

"  Think(of(a(live(version(of(the(popular(Pacman(game(!!(

"  Could(be(an(advanced(“Google(LaBtude”(or(“Facebook(Places”(app(

!  Methodology:(

"  other(objects(are(routed(to(a(point(where((

the(target(object(is(esBmated(to(arrive((

a|er(a(Bme(interval(

"  this(“meeBng(point”(is(periodically((

refreshed(

55#

GetKtogether#(cont.)#

!  Challenge:(future&loca3on&predic3on(!!(

56#

Summarizing#…#

!  So(far,(we’ve(seen(a(variety(of(mobileOaware(applicaBons(

"  From(‘smart’((updated(in(realOBme)(rouBng(to(mobile(social(

networking((Google(LaBtude,(Facebook(Places,(etc.)(

!  Internally((either(at(server(or(client(side),(what(kinds(of(opera3ons(should(be(efficiently(supported?("  Core(database(/(computaBonal(geometry(operaBons(

"  GraphObased(operaBons(

"  Trajectory(management(operaBons(

57#

Operations#to#be#supported#

!  Core(database(/(computaBonal(geometry(operaBons(

"  Window&search:(selects(points(within(a((circular(or(rectangular)(window(

"  k4NN&search:(selects(the(kO(nearest(points(to(an(object((point(or(region)(

"  Euclidean&distance&calcula3on:(calculates(the(Euclidean(distance(between(two(points(

"  Path&length&rou3ne:(calculates(the(length(of(a(path(

!  GraphObased(operaBons(

!  Trajectory(management(operaBons(

58#

Operations#to#be#supported#(cont.)#



"  Rou3ng:(finds(the(opBmal(route(between(two(points((taking(into(

consideraBon(a(number(of(constraints)(

"  Network&distance&calcula3on:(calculates(the(network(distance(between(two(points(

"  Network&k4Nearest&Neighbor&search:(searches(for(the(kONN(of(a(point(with(respect(to(network(distances(


59#

Operations#to#be#supported#(cont.)#




"  Trajectory&refresh:(adds(a(new(coming(posiBon(to(an(exisBng(

trajectory(

"  Trajectory&projec3on:(esBmates(the(posiBon(of(an(object(at(a(future(

Bme((taking(into(consideraBon(its(history)(

"  Trajectory4based&search:((spaBal(and/or(temporal)(window(search,(NN(

search,(trajectory(similarity(search,(etc.(

60#

The#big#picture#

61#

62#

The#modules#of#our#architecture#

raw data producers

(Semantic) Trajectory

aggregations (DW)

Mobility Data

Visual-ization

(Semantic) Mobility Data

Querying

(Semantic) Mobility

Data Mining

Extract-Transform-

Load (ETL)

Trajectory reconstruction

Raw location recordings (DB)

Home (breakfast) office (work) Market (shopping) Home (relax)

Road (bus)

Train (metro)

Sideway (walk)

[~, 8am]

[8am, 9am] [6pm, 6:30am] [7:30pm, 8pm]

[9am, 6pm] [6:30pm, 7:30pm] [8pm,~]

Trajectories (MOD)

Semantic enrichment

Semantic Trajectories (STD)

(Semantic) Mobility

Data OLAP

PoI DB

+

+

63#

Key#questions#that#arise#

!  How(to(reconstruct&a&trajectory(from(raw(logs?((

!  How(to(store&trajectories(in(a(DBMS?(

"  Is(a(trajectory(simply(a(sequence(of((x,(y,(t)(tuples?(

!  What(kind(of(analysis&is(suitable(for(mobility(data?((

"  In(parBcular,(trajectories(of(moving(objects?(

"  How(does(infrastructure((e.g.(road(network)(affect(this(analysis?(

!  Which(paRerns&/&models&can(be(extracted(out(of(them?(

"  Clusters,(frequent(paNerns,(anomalies(/(outliers,(etc.(

"  How(to(compute(such(paNerns(/(models(efficiently?(

!  How(to(protect&privacy&/&anonymity?("  Looking(for(the(tradeOoff(between(privacy(protecBon(and(quality(of(analysis(

64#

Course#outline#

I.&Introduc3on&–((DefiniBon(of(trajectory(data;(GeoOposiBoning(technologies;(LocaBonO

aware(applicaBons(

II.&Background&–((SpaBal(database(management(and(exploraBon(

III.&Mobility&data&management&–((Acquiring(trajectories(from(raw(data;(LocaBonOaware(querying;(

Efficient(trajectory(indexing(and(storage(in(MODs(

IV.&Mobility&data&explora3on&–((Trajectory(warehousing(and(OLAP;(Mobility(data(mining(and(

reasoning;(Visual(analyBcs(for(mobility(data(

V.&Privacy&aspects&–((Preserving(user(traces’(anonymity(

VI.&Outlook&–((Open(issues;(Future(challenges(

65#

Questions#

End(of(section#

I.#Introduction · 5# Introduction,#Overview# From digital mapping to mobile social networking –...

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