WalkCompass: I am a Smartphone and I can Tell my User’s Walking Direction MobiSys 2014, Bretton Woods, NH Nirupam Roy He Wang Romit Roy Choudhury ! !
Indoor Localization: Chasing Accuracy Location Accuracy 2 Meter 50 Centimeter 3 Meter 1 Meter Mean 2000 2004 2007 2010 2013
Indoor Localization: Chasing Accuracy Location Accuracy 2 Meter 50 Centimeter 3 Meter 1 Meter Mean 95 th Percentile 2000 2004 2007 2010 2013
Hardware Walking Map/ Step Device Homogeneity Direction Floor plan Length Orientation …
Walking Direction
Walking Direction: The Definition Walking Direction 8!
Walking Direction: The Definition 9!
Why Not Compass ? 10!
Why Not Compass? Y axis 60° NE N 60° NE
Why Not Compass? Y axis Y axis 30° NE 60° NE N N 60° NE 12!
Why Not Compass? Y axis Y axis 60° NE 30° NE N N Walking Direction Walking Direction 60° NE 13!
Why Not Compass? Compass Direction �� Walking Direction 14!
Walking Direction Force Force 15!
Challenges 16!
Challenge 1: Finding the Right Force Complex combination of forces 17!
Challenge 2: Finding Common Solution Different walking patterns Different phone locations 18!
Understanding a Walk Signal Raw accelerometer signal Phone Location: Pants pocket 19!
Understanding a Walk Signal Foot!step! Body!movement! Leg!touches! ground! Leg!swing! Raw accelerometer signal Phone Location: Pants pocket 20!
Segmentation of the Signal: Key Intuition 21!
Technique Overview 22!
Anatomy of a Human Walk Swing Phase (40%) Stance Phase (60%) Heel-touch Heel-touch Heel-touch (Right) (Left) (Right) 23! Raw Accelerometer Signal
Anatomy of a Human Walk Swing Phase (40%) Stance Phase (60%) Heel-touch Heel-touch Heel-touch (Right) (Left) (Right) 24! High Frequency Components
Anatomy of a Human Walk Swing Phase (40%) Stance Phase (60%) Heel-touch Heel-touch Heel-touch (Right) (Left) (Right) 25! Heel-touch Detection Signal
Anatomy of a Human Walk Swing Phase (40%) Stance Phase (60%) 26! Raw Accelerometer Signal
Anatomy of a Human Walk Swing Phase (40%) Stance Phase (60%) 27! Low Frequency Components
Anatomy of a Human Walk Swing Phase (40%) Stance Phase (60%) 28!
Anatomy of a Human Walk Swing Phase (40%) Stance Phase (60%) 29!
Anatomy of a Human Walk Swing Phase (40%) Stance Phase (60%) 30!
Walking Direction Vector W 3D 31!
Walking Direction Vector W 3D Y W 2D 32!
Global Walking Direction 60° North-East W 2D 33!
But… 34!
Global Walking Direction W 2D 35!
Compass: How Reliable is this? 36!
Compass Correction 37!
Compass: How It Works N S 38!
Compass: Effect of Interference N Ferromagnetic Material S 39!
Compass: Effect of Interference N Ferromagnetic Material S 40!
Compass: Effect of Interference N R esultant I nterference G eo-mag R = G + I - G = I R 41!
Iterative Magnetic Triangulation (IMT) 42!
Iterative Magnetic Triangulation (IMT) - = G correct R I R G correct I 43!
Iterative Magnetic Triangulation (IMT) - = G incorrect R I R G incorrect I 44!
Evaluation 45!
Methodology
Error in Walking Direction 150 Absolute Error (degree) Median 75th Percentile 100 50 0 0 10 20 30 Number of Steps 47!
Error in Walking Direction 150 Absolute Error (degree) Median 75th Percentile 100 Error!converges!to!8°!! within!6!steps! 50 0 0 10 20 30 Number of Steps 48!
Better Compass 90 90 120 60 120 60 150 30 150 30 180 0 180 0 210 330 210 330 240 300 240 300 270 270 Today’s Corrected Compass Compass (IMT Algorithm) 49!
Better Compass 90 90 120 60 120 60 150 30 150 30 180 0 180 0 Error!±40°! Error!±10°! 210 330 210 330 240 300 240 300 270 270 Today’s Corrected Compass Compass (IMT Algorithm) 50!
Discussion and Future Work - Convergence time of the system - Performance when the phone is in a bag 51!
Conclusion 52!
Thank You. SyNRG!@!UIUC! hCp://synrg.csl.illinois.edu! hCp://synrg.csl.illinois.edu/projects/localizaSon/ walkcompass!
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