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1 “Did you see Bob?”: Human Localization using Mobile Phones Ionut Constandache Co-authors: Xuan Bao, Martin Azizyan, and Romit Roy Choudhury Modified by Chulhong
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2 Localization Technologies Outdoor Driving directions GPS, Skyhook Indoor Localization in office Cricket, Radar, BAT Energy-Efficient Continuous localization EnLoc, RAPS Logical Context-aware ads SurroundSense
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3 Localization Technologies Outdoor Driving directions GPS, Skyhook Indoor Localization in office Cricket, Radar, BAT Energy-Efficient Continuous localization EnLoc, RAPS Logical Context-aware ads SurroundSense Human Localization: Guiding a user to finding another person Human Localization: Guiding a user to finding another person
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4 Usage Scenario Bob Alice
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5 Usage Scenario Where is Bob? Please escort me to Bob. Bob Alice
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6 Usage Scenario Where is Bob? Bob Alice
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7 Usage Scenario Where is Bob? Bob Alice General approach today: 1.Stroll around in the hotel until Alice can visually spot Bob 2.Ask “Have you seen Bob around?” 3.Phone call However, what if Alice does not know Bob?
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8 Usage Scenario Where is Bob? Please escort me to Bob. Bob Provide an electronic Escort system. Alice
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9 Usage Scenario Alice’s Phone 20 steps North 5 steps East N Bob
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10 Usage Scenario Alice’s Phone
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11 Usage Scenario Alice’s Phone Bob
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12 Human Localization Finding Bob in unfamiliar place (E.g. library, mall, engineering building)
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13 Human Localization Finding Bob in unfamiliar place (E.g. library, mall, engineering building)
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14 Human Localization Finding Bob in unfamiliar place (E.g. library, mall, engineering building) Better for Alice to be escorted to Bob
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15 Human Localization Finding Bob in unfamiliar place (E.g. library, mall, engineering building) Better for Alice to be escorted to Bob Challenges: Bob’s location unknown Challenges: Bob’s location unknown
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16 Human Localization Finding Bob in unfamiliar place (E.g. library, mall, engineering building) Better for Alice to be escorted to Bob Challenges: Bob’s location unknown Even if known still require … WALK-able routes to Bob Challenges: Bob’s location unknown Even if known still require … WALK-able routes to Bob
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17 Human Localization Finding Bob in unfamiliar place (E.g. library, mall, engineering building) Better for Alice to be escorted to Bob Challenges: Bob’s location unknown Even if known still require … WALK-able routes to Bob Once in his vicinity, identify Bob Challenges: Bob’s location unknown Even if known still require … WALK-able routes to Bob Once in his vicinity, identify Bob
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Can current localization schemes help?
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too heavy on requirements … Infrastructure: specialized hardware (e.g. Cricket, BAT, etc.) or War-driving: build fingerprint DB (e.g. Radar, Skyhook, etc.) Can current localization schemes help?
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too heavy on requirements … Infrastructure: specialized hardware (e.g. Cricket, BAT, etc.) or War-driving: build fingerprint DB (e.g. Radar, Skyhook, etc.) … need lightweight localization solution Can current localization schemes help?
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21 Contents Escort Evaluation Limitations and Future Work Conclusion
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22 Contents Escort Evaluation Limitations and Future Work Conclusion
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23 Our Solution Accelerometers/compasses track human movements Standard sensors in mobile phones Each user has a trail trail
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24 Our Solution Accelerometers/compasses track human movements Standard sensors in mobile phones Each user has a trail trail step i, direction i > = TRAIL <
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25 Our Solution Accelerometers/compasses track human movements Standard sensors in mobile phones Each user has a trail trail
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26 Our Solution Deploy coordinate system to localize users Any (fixed) location can be the origin N, E directions are the Y, X axises N E Origin
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27 Our Solution Users join the coordinate system When passing the origin At encounters with users already in the system (0,0) N E Origin
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28 Our Solution Users join the coordinate system When passing the origin At encounters with users already in the system N E Origin (x,y)
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29 Our Solution Users join the coordinate system When passing the origin At encounters with users already in the system N E Origin (x,y)
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How does Escorting work?
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C A B D
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C A B D Escort Service Cloud A’s Trail
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C A B D Escort Service Cloud A’s Trail
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C A B D Escort Service Cloud
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C A B D Escort Service Cloud
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C A B D I BD I BC I AC Escort Service Cloud
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C A B D I BD I BC I AC Escort Service Cloud
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C A B D I BD I BC I AC I BC I BD A CB D Trail Graph Escort Service Cloud
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39 Trail Graph I AC I BC C B D I BD A
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40 Escort along the Trail Graph I AC C D I BD B I BC Alice Bob A
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41 Escort along the Trail Graph I AC C D I BD B I BC Alice Bob A
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42 Escort along the Trail Graph I AC C D I BD B I BC Bob A Alice
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43 Escort along the Trail Graph I AC C D I BD B I BC Bob A Alice WALK-able routes Alice guided along user trails: Trails need to be accurate Alice guided along user trails: Trails need to be accurate
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44 Challenges Trails drift: acc. missed steps, compass biases t1t1 t2t2
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45 Challenges Trails drift: acc. missed steps, compass biases t1t1 t2t2
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46 Challenges Trails drift: acc. missed steps, compass biases t1t1 t2t2
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47 Challenges Trails drift: acc. missed steps, compass biases t1t1 t2t2
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48 Challenges Trails drift: acc. missed steps, compass biases t1t1 Compass bias t2t2 θ
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49 Challenges Trails drift: acc. missed steps, compass biases t1t1 t2t2
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50 Challenges Trails drift: acc. missed steps, compass biases t1t1 t2t2
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51 Challenges Trails drift: acc. missed steps, compass biases t1t1 t2t2
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52 Challenges Trails drift: acc. missed steps, compass biases t1t1 t2t2
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53 Challenges Trails drift: acc. missed steps, compass biases t1t1 Actual Drifted t2t2
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54 Challenges Trails drift: acc. missed steps, compass biases t1t1 Actual Drifted t2t2
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55 Challenges Trails drift: acc. missed steps, compass biases t1t1 Actual Drifted t2t2 Error
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56 Challenges Trails drift: acc. missed steps, compass biases t1t1 Actual Drifted t2t2 Error Need to correct: User Location User Trail Need to correct: User Location User Trail
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57 Correct User Location Opportunities When passing the origin, the user is at (0,0) Close-encounters with users who passed the origin recently Take this user’s position (it’s accurate) N E Origin
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58 Correct User Location Opportunities When passing the origin, the user is at (0,0) Close-encounters with users who passed the origin recently Take this user’s position (it’s accurate) N E Origin
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59 Correct User Location Opportunities When passing the origin, the user is at (0,0) Close-encounters with users who passed the origin recently Take this user’s position (it’s accurate) N E Origin
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60 Correct User Location Opportunities When passing the origin, the user is at (0,0) Close-encounters with users who passed the origin recently Take this user’s position (it’s accurate) N E Origin Encounter with origin (0,0)
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61 Correct User Location Opportunities When passing the origin, the user is at (0,0) Close-encounters with users who passed the origin recently Take this user’s position (it’s accurate) N E Origin Encounter with origin (0,0)
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62 Correct User Location Opportunities When passing the origin, the user is at (0,0) Close-encounters with users who passed the origin recently Take this user’s position (it’s accurate) N E Origin Encounter with origin (0,0)
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63 Correct User Location Opportunities When passing the origin, the user is at (0,0) Close-encounters with users who passed the origin recently Take this user’s position (it’s accurate) N E Origin Encounter with phone with good location estimate (x,y)
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64 Correct User Location Opportunities When passing the origin, the user is at (0,0) Close-encounters with users who passed the origin recently Take this user’s position (it’s accurate) N E Origin Encounter with phone with good location estimate (x,y)
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65 Correct User Location Opportunities When passing the origin, the user is at (0,0) Close-encounters with users who passed the origin recently Take this user’s position (it’s accurate) N E Origin Encounter with phone with good location estimate (x,y) How to detect encounters with origin/users?
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66 Detecting Encounters using Sound Phones periodically beacon their presence Beacons = unique audio tones Phones also listen for neighboring beacons
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67 Detecting Encounters using Sound Phones periodically beacon their presence Beacons = unique audio tones Phones also listen for neighboring beacons Tone amplitude above threshold encounter
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68 Correct User Trail Actual Drifted t1t1 t2t2 Error
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69 Origin Correct User Trail Actual Drifted t1t1 t2t2 Error
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70 Origin t1t1 Correct User Trail Actual Drifted t2t2
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71 Origin t1t1 Correct User Trail L(t) L’(t) t2t2 Actual Drifted
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72 Origin t1t1 Correct User Trail Actual Drifted Corrected L(t) L’(t) t2t2
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73 Escort After drift correction Escort users along the corrected trails Place user in vicinity of the searched-for person
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74 Escort After drift correction Escort users along the corrected trails Place user in vicinity of the searched-for person I BC I BD A C B D I AC
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75 Escort After drift correction Escort users along the corrected trails Place user in vicinity of the searched-for person E F I BC I BD A C D I AC B
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76 Escort After drift correction Escort users along the corrected trails Place user in vicinity of the searched-for person E F I BC I BD A C D I AC How to visually identify Bob? B
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77 Solve human localization end-to-end Create visual fingerprint for each user Alice’s Phone Bob Visual Identification
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78 Visual Fingerprint User picture
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79 Visual Fingerprint Upper Region Lower Region Fingerprint User picture
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Recognizing Bob
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Users advertise
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Recognizing Bob Alice’s Phone
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Recognizing Bob Alice’s Phone
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Recognizing Bob Alice’s Phone
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Recognizing Bob Alice’s Phone Bob
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86 Contents Escort Evaluation Limitations and Future Work Conclusion
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87 Evaluation Escort target accuracy: several meters Require high ground-truth accuracy ~ 1m GPS not accurate enough Our approach Run experiments in a testbed with dense markers Markers have known position
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88 A C D 36 m 48 m Testbed Markers Origin B
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89 A C D 36 m 48 m Testbed Markers Origin User Paths B
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90 A C D 36 m 48 m Testbed Markers Origin User Paths B 4 Test Users 13 minutes experiment User locations known at markers 40 escorting tests
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91 Average Localization Error Average Localization Error across all users: ~ 6m
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92 Final Distance from Destination Average Error at end of escorting: ~ 8m
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93 Visual Identification Accuracy
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94 Contents Escort Evaluation Limitations and Future Work Conclusion
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95 Limitations and Future Work Employees only access Trails may have restrictions Phone placement Assumed in hand, investigate placement as future work Imprecise navigation Humans can make educated guesses Testing under heavy user load
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96 Conclusions We asked ourselves: Can mobile phones help in “routing” a person A to a person B Challenging because: Require walkable routes Needs to be free of infrastructure, war-driving Possible because: Rich sensing capabilities on mobile phones High density of such devices
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97 Conclusions Our approach: “Stitching” human walking traces to compose a graph. Route humans on this walkable graph Solution is analogous to routing in DTNs … Only packets are now humans Alice Bob
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98 Questions? Thank You! Visit the SyNRG research group @ http://synrg.ee.duke.edu/
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