This was a project with Nokia, building a basis towards life sensing. In particular, accelerometer is not too strong in detecting in-vehicle mode. We used the data-driven approach and teased out a couple of other non-GPS sensors that appear strong for user in-vehicle detection.

1. Towards Life Sensing
Barometer-‐based in-‐vehicle detection
Jialing Li
October 2014
Internal Use Only

2. Contextual sensing
Motivation 1:
Context-‐aware apps can tailor user experience (﴾e.g. switching on the
audio interface when user is driving)﴿.
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3. Smartphone as a virtual assistant
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Commuting to work
on my scenic back road
Meeting got
rescheduled
to an earlier slot
Re-‐routing to a
faster path
+

4. Contextual sensing
Motivation 2:
Machine-‐learning algorithms (﴾such as voice recognition)﴿ perform more
accurately when contextual information is supplied.
Internal Use Only

5. How does barometer-‐based
in-‐vehicle detection work?
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7. Vertical Speed ~ the Rate of Pressure Change
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Wikipedia

8. Feature Engineering
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9. Internal Use Only
Smoothed Speed
“Drive” Labeled
Air Pressure
"/"$ ![&'(!)(*++,(*]
Smoothed "/"$ ![&'(!
)(*++,(*]
Threshold of ↑ at
0.005
Median of Smoothed
"/"$ ![&'(!)(*++,(*]
Threshold of ↑ at
0.007
Reference
Generating
input for
model

10. Visual inspection of separation between two classes
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11. Visual inspection of separation between two classes
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12. Accuracy measurement
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13. Internal Use Only
Air Pressure
"/"$ ![&'(!)(*++,(*]
Smoothed "/"$ ![&'(!
)(*++,(*]
Threshold of ↑ at
0.005
Median of Smoothed
"/"$ ![&'(!)(*++,(*]
Threshold of ↑ at
0.007
Prediction
Prediction binned on
each 30 seconds
Ground Truth
>reported by user BB
Generating
input for
model
Output
from
model
Ground
Truth

14. Towards a Population Model
Random Forest
Train on one set of users and test on another set
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15. Internal Use Only
Next: Trip Recognition

17. One major area that needs improvement
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18. Slow%Driving%is%Hard%to%Detect
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detected%
annotated%
300%sec%lag% 60%sec%ahead%%
Low%Speed% Low%Speed%

19. What other sensors can we use?
-‐ work in progress
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20. 1)﴿ Audio sensor
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21. Harmonics*in*car*engine*noise
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22. Harmonics*in*car*engine*noise
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4/2 ! 2200/60 !=!73.33!Hz!

23. Harmonics*in*car*engine*noise
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Increasing*engine*RPM*

24. Harmonics*FFT of an auidni*os acmlipp ldeu*crilnipg
and after ignition
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25. Harmonics*Not every cliinp* sisa mthpisl ec*leclaipn
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26. Borrowing concepts from voice recognition
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27. Engine on and not idling
Engine off
Engine idling

28. Engine idling
Engine on and not idling
Engine off

29. Potential issues with audio
• Privacy concerns
• Battery drain is huge if continuously
sampled (a barometer-audio hybrid
solution could reduce this problem)
• Sound from other cars = false detection
(need a hybrid solution and/or a system
with memory)

30. 2)﴿ Compass sensor
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31. • Field strengths
differ at different
locations inside the
car
• Degree of tire
magnetization
varies among
different brands

32. On
Engine State FFT of Compass Speed 16
Off
10
0
0
car entry?

33. As expected,
clear patterns only exist
for a limited number of brands.
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34. Summary
• Before us, in-vehicle detection relies mostly on GPS,
accelerometer and gyroscope sensors.
• Our POC model using barometer sensor shows huge
improvement in in-vehicle detection over the state-of-the-
art commercial-grade accelerometer-based model.
• The issue with slow-drive can be remedied with audio
(and occasionally compass) sensor.

35. More on barometer
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36. Extension to other
transportation modes