PARKNET: DRIVE-BY SENSING OF ROAD-SIDE PARKING STATISTICS Suhas Mathur, Tong Jin, Nikhil Kasturirangan, Janani Chandrashekharan, Wenzhi Xue, Marco Gruteser, Wade Trappe MobiSys ‘10 - Sowhat 2010.7.21
Mar 31, 2015
PARKNET: DRIVE-BY SENSING OF ROAD-SIDE PARKING STATISTICS
Suhas Mathur, Tong Jin, Nikhil Kasturirangan, Janani Chandrashekharan, Wenzhi Xue, Marco Gruteser, Wade Trappe
MobiSys ‘10
- Sowhat 2010.7.21
OUTLINES Motivation Objective Related Works ParkNet
Overview Hardware Deployment Detection Environmental positioning correction Viability
Discussion Conclusion
OUTLINES Motivation Objective Related Works ParkNet
Overview Hardware Deployment Detection Environmental positioning correction Viability
Discussion Conclusion
MOTIVATION Societal costs due to traffic congestion
Parking
Lack of information
Value of real-time information Government – adjusting prices Driver – suggested parking spaces, better
decision
OUTLINES Motivation Objective Related Works ParkNet
Overview Hardware Deployment Detection Environmental positioning correction Viability
Discussion Conclusion
OBJECTIVE
Providing parking information inslotted / unslotted areas
Parking information - Space Count Occupancy Map
OUTLINES Motivation Objective Related Works ParkNet
Overview Hardware Deployment Detection Environmental positioning correction Viability
Discussion Conclusion
RELATED WORKS SF-park project - Stationary sensor network
Sensor node installed in the center of each parking spot
Repeaters and forwarding nodes for connectivity Centralized parking monitoring system
Drawbacks of SF-park project Large installation and maintenance cost Limited to slotted parking spots Wireless relay nodes needed
OUTLINES Motivation Objective Related Works ParkNet
Overview Hardware Deployment Detection Environmental positioning correction Viability
Discussion Conclusion
PARKNET - OVERVIEW
Ultrasonic rangefinder GPS receiver
OUTLINES Motivation Objective Related Works ParkNet
Overview Hardware Deployment Detection Environmental positioning correction Viability
Discussion Conclusion
PARKNET - HARDWARE Ultrasonic sensors
Why ultrasonic? Low cost – compared to laser rangefinder Nighttime operation – compared to camera Increasing availability to support parking functions
Setting Range >= half the width of roads, 12~255
inches(0.3~6.5m) Sampling rate – several samples over the length of a car,
50ms
PARKNET - HARDWARE On-board PC
1GHz CPU 512MB RAM 20GB hard disk Atheros 802.11 a/b/g mini PCI card 6 USB 2.0 ports
GPS receiver Garmin 18-5Hz GPS 12 channel receiver 5 GPS readings / sec WAAS correction of errors less than 3 meters
Parking estimation server
OUTLINES Motivation Objective Related Works ParkNet
Overview Hardware Deployment Detection Environmental positioning correction Viability
Discussion Conclusion
PARKNET - DEPLOYMENT 3 vehicles 2 month 3 road-side area
(57 marked slotted parking spots/ 734m / 616m)
Total of more than ~500 miles of data Camera for ground truth GPS trip-boxes
Trigger to collect data Guard distance/time
OUTLINES Motivation Objective Related Works ParkNet
Overview Hardware Deployment Detection Environmental positioning correction Viability
Discussion Conclusion
PARKNET – DETECTIONSENSOR READING
PARKNET – DETECTIONFLOW & PRE-PROCESSING
Pre-processing Removing dips that have
too few readings < 6 sensor readings Assuming
max speed = 37 mph(58.2km)a car length = 5 m
PARKNET – DETECTIONFILTERING Comparing the width and depth of each dip
against thresholds
Threshold = the values make the minimum overall error rate
Overall error rate = false positive rate + miss detection rate
Depth >= 89.7 inches (2.27meters)Width >= 2.52 meters
PARKNET – DETECTIONWIDTH CLASSIFICATION Slotted
Dips of a width > 2*threshold 2 cars
UnslottedEstimating the spatial distance between
dips that have been classified as parked cars
Comparing the distance to the length of a standard parking space (6 meters)
PARKNET – DETECTIONMETRICS & EVALUATION Missed detection rate pm
False positive rate pf
Slotted – n’/ nUnslotted – d’/ d
OUTLINES Motivation Objective Related Works ParkNet
Overview Hardware Deployment Detection Environmental positioning correction Viability
Discussion Conclusion
PARKNET - ENVIRONMENTAL POSITIONING CORRECTION
GPS ERROR CORRELATION
PARKNET - ENVIRONMENTAL POSITIONING CORRECTION
ENVIRONMENTAL FINGERPRINTING
Comparing reported location of the pattern produced by fixed objects Priori known location of this pattern
Error vectorei(x,y) = ti(x,y) – li(x,y)
ti(x,y) : the true location of object i
li(x,y) : the location stamp of object i
Adding error vector to the location estimates of all detected cars within 100m of this object
PARKNET - ENVIRONMENTAL POSITIONING CORRECTION
EVALUATION Using Hungarian algorithm to match cars to
parking spots
OUTLINES Motivation Objective Related Works ParkNet
Overview Hardware Deployment Detection Environmental positioning correction Viability
Discussion Conclusion
Areas with greater amount of street parking utilization= areas with greater presence of taxis
Cost
Why ParkNet better? Nonguaranteed, random sampling
PARKNET - VIABILITY
ParkNet SF-park
Cost 400 / vehicle 250-800 / spot
Number 300 taxis 6000 spots
Total 120,000 1,500,000
OUTLINES Motivation Objective Related Works ParkNet
Overview Hardware Deployment Detection Environmental positioning correction Viability
Discussion Conclusion
DISCUSSION Multilane roads
Speed limitations
Obtaining parking spot maps
OUTLINES Motivation Objective Related Works ParkNet
Overview Hardware Deployment Detection Environmental positioning correction Viability
Discussion Conclusion
CONCLUSION ParkNet providing road-side parking info
Space countOccupancy map
300 taxis updating every ~25min for 80%
Some technical problems while implementing to real life
THANKS FOR LISTENING ~