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What to Do With Thousands of GPS Tracks
John Krumm, PhDMicrosoft Research
Redmond, WA
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GPS DataMicrosoft Multiperson Location Survey (MSMLS)
55 GPS receivers227 subjects1.77 million points95,000 miles153,000 kilometers12,507 tripsHome addresses & demographic data
Greater Seattle Seattle Downtown Close-up
Garmin Geko 201$11510,000 point memorymedian recording interval
6 seconds63 meters
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Personalized Routes
Percentage of trips in our data for which the driver’s actual route matched the…
Shortest route: 27%Fastest route: 31%MapPoint route: 39%Neither shortest nor fastest: 60%
Empirically fastestShortest distance
MapPoint plan
Driver’s route
One Driver A to B:
Julia Letchner, John Krumm, and Eric Horvitz, "Trip Router with Individualized Preferences (TRIP): Incorporating Personalization into Route Planning", Eighteenth Conference on Innovative Applications of Artificial Intelligence (IAAI-06), July 2006.
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Preferable Routes
One trip from GPS data
• Deflate cost of previously driven roads• Tested on ~2500 trips
• 47% of computed routes matched actual• Only 11% of trips duplicated in data
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Dynamic Map Matching
measured GPS points
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Goal: Infer actual route from noisy location data
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John Krumm, Julie Letchner, and Eric Horvitz, "Map Matching with Travel Time Constraints", Society of Automotive Engineers (SAE) 2007 World Congress, April 2007, Paper 2007-01-1102.
Results on traditional problem cases
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PredestinationWhere do you want to go today? We already know.
Traffic WarningDestination Safeco Field (54% chance): 15-minute delay at I-405 & I-90. Suggest I-5 instead.
Destination Seattle Center (31% chance): Broad St. closed. Suggest Denny Way instead.
Going to the airport? Park with us for $8/day!
Regular nav system Upcoming traffic Relevant ads
Optimize hybrid charge/discharge
John Krumm and Eric Horvitz, "Predestination: Inferring Destinations from Partial Trajectories", Eighth International Conference on Ubiquitous Computing (UbiComp 2006), September 2006.
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Predestination• Previous destinations• Preferred ground cover• Efficient driving• Anticipated trip times
USGS Ground Cover: swamps unpopular as destination
(1) (2) (3)
Median error = 2 kilometers at halfway point of trip
John Krumm and Eric Horvitz, "Driver Destination Models", Eleventh International Conference on User Modeling (UM 2007), June 25-27, 2007, Corfu, Greece.
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Location Privacy
Congestion Pricing Location Based Services Pay As You Drive (PAYD) Insurance
Collaborative Traffic Probes (DASH) Research (London OpenStreetMap)
John Krumm, "Inference Attacks on Location Tracks", Fifth International Conference on Pervasive Computing (Pervasive 2007), May 13-16, 2007, Toronto, Ontario, Canada.
Why reveal your location to a 3rd party?
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Attack Outline
Relative Probability of Home vs. Time of Day
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Time (24 hour clock)
Pro
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8 a.m. 6 p.m. Median error = 61 meters
Correct name on 5%
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Computational Countermeasures
Uncorrupted Data Spatial Cloaking
Gaussian Noise, σ = 50 m Discretize, Δ = 50 mMention this talk at any participating* Pizza Hut and receive free breadsticks!* There are actually no participating Pizza Huts.
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How Much Corruption?
Accuracy Effects
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Gaussian Noise, σ = 50 m Discretize, Δ = 50 m