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Sparse Mat: A Tale of Devising A Low-Cost Directional System for Pedestrian Counting
Department of Computer Science and Engineering,Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
NSysS 2017Dhaka, Bangladesh
Tarik Reza Toha, Salman Estyak, Taslim Arefin Khan, Tusher Chakraborty, and A. B. M. Alim Al Islam
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Outline
• Background and motivation• Our proposed system– Design– Implementation– Experimentation
• User evaluation• Conclusion and future work
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Background: Pedestrian Counting
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Applications of Pedestrian Counting
• Strategic business research – Tourist flow estimation
• Security and emergency support– Victim count estimation
for rescue operations• Optimization tasks– Railway stations,
shopping malls, airports, hospitals, etc.
Assign staff deployment to demand
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Classical Pedestrian Counting Technique
• Low human mobility– Using pen and paper,
or tally counter
• High human mobility– Automated pedestrian counter is
required
?
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Existing Automated Counting Techniques
Pros: High accuracy
Cons: High cost High power
Pros: Low-cost Low-power Easy setup process
Cons: Low accuracy
Laser scanner counter[Katabira et al., ACRS, 2004]
Infrared beam counter[Wienand et al., USPTO, 2001]
Cons: High cost Complex algorithms High processing power
Pros: High accuracy
Camera-based counter[Agusta et al., ICCEMS, 2014]
Existing high-end device based solutions are high-cost
and high-power
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Existing Mat-Based Counting Technologies
Greneker et al., 1996(2000 sensors/sq. ft.)
Kutschera et al., 2011(90 sensors/sq. ft.)
Instant Counting Mat by Milon et al., 2013(56 sensors/sq. ft.)
Existing mat-based solutions demand high densities of
expensive sensors
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Our Contribution
We propose a mat-based pedestrian counting solution comprising low density (~3 sensors/sq. ft.) of low-cost sensors, which exhibits a high accuracy in pedestrian
counting
Sparse Mat
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Underlying Sensing Mechanism
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Sparse Mat: Operational Block Diagram
Block diagram
Cross sectional view of sensing module
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Snapshot of Sparse Mat
Sensing Module Controller Module
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Piezoelectric Sensor Responses for Varying Radial Distances
Piezoelectric sensor responses under varying points of pressure over the hardboard block
Coverage of piezoelectric sensor response
Vibration propagation while knocking on a hardboard block, which covered a
piezoelectric sensor
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Sensing Step-Down Phenomena
Sensor placement over mat Sensor placement along with taped foam
Hardboard block placement over sensors
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Findings from 2×2 Piezo-grid
Piezoelectric sensor responses while moving towards from down row to up row over the left sensors
Piezoelectric sensor responses while moving towards from up row to down row over the right sensors
drdl
ul ur
drdl
ul ur
The varying response time can significantly undermine the accuracy of directional
pedestrian counting
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Resilience to Variation in Response Time: 2×3 Piezo-grid?
Sensor placement over mat Sensor placement along with taped foam
Hardboard block placement over sensors
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Findings from 2×3 Piezo-grid
Piezoelectric sensor responses while moving towards from down row to up row
Piezoelectric sensor responses while moving towards from up row to down row
drdl
ul ur
dm
um
drdl
ul ur
dm
um
The ending always maintains perfect order even though
starting may not!
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Sensing Step-up Phenomena
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Modified Settings in 2×3 Piezo-grid
Sensor placement over mat Sensor placement along with taped foam
Hardboard block placement over sensors
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Enhancing Sensing Accuracy: 3×2 Piezo-grid
Sensor placement over mat Sensor placement along with taped foam
Hardboard block placement over sensors
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User Evaluation of Preliminary Designs
Grid Sensing Phenomena Accuracy (%) Causes
2×2 Step-Down < 50 Response time varies significantly from sensor to sensor
2×3 Step-Down 60 Time delay between placing heel and toe is very small
2×3 Step-Up 75 Participants often failed to place their foot step over both hardboard blocks
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User Evaluation of the Final Design: 3×2 Piezo-grid Sensing Step-Up
Age Height (inch)
Weight (kg)
Shoe length (inch) Total attempts Successful
detectionDevice
accuracy (%)22 66 68 11 18 14 7822 70 62 11.25 20 20 10022 73 81 12 10 8 8023 70 90 11.25 20 20 10025 68 72 11.25 20 20 10026 66 55 11 8 7 88
Total 96 89 93
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Conclusion and Future Work
• Existing automated directional pedestrian counters are generally highly expensive
• We propose a low-cost and easily-to-deploy automated directional pedestrian counter without compromising accuracy– Uses sparser sensors than any other state-of-the-art technologies
94% sparser than Instant Counting Mat
– User evaluation of real implementations confirms an average accuracy of 93%
• Future work– Workable for different types of users such as kids– Determine multiple footsteps of a single person– Determine multiple persons traversing in parallel over the sensor mat
A Short Demonstration of Sparse Mat
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• https://youtu.be/C7MB58Xvr_w
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Variable Sensor Response Times
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Towards Sensing Step-up Phenomena (contd.)
Flowchart of step-down phenomena sensing algorithm
Flowchart of step-up phenomena sensing algorithm
