Sensors and location based services
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This document discusses sensors and location-based services on Android devices. It describes several types of sensors including compass, gyroscope, accelerometer, barometer, and GPS. It provides examples of how these sensors can be used in applications for active input, passive input, active-passive functions, and auto-rotate capabilities. The document also offers tips for sensor calibration, polling rates, sensor fusion, and managing sensor event listeners and wake locks in apps.
Sensors and location based services
- 1. SENSORS AND LOCATION BASED SERVICES ChinmayVS @ B.A.(U).G 14 JAN 2012
- 2. Sensors & location based services • Compass - Bearing • Gyroscope, Accelerometer - Detect motion. • Barometer - Calculate Altitude. • nGPS http://goo.gl/RWEKL (Experimental.) SENSORS AND LOCATION BASED SERVICES 2
- 3. cvs@BA(U)G$ who am i • Android >2yrs. Remember anyone? • - sensors development. 10million+ units sold. • Presently working @ PathPartnerTech.com SENSORS AND LOCATION BASED SERVICES 3
- 4. “Sense-ors” on Android A sensor (also called detector) is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. 1. ACCELEROMETER 2. GYROSCOPE 3. MAGNETIC_FIELD REAL 4. LIGHT 5. PRESSURE 6. AMBIENT_TEMP 7. RELATIVE_HUMIDITY 8. PROXIMITY VIRTUAL 9. LINEAR_ACCELERATION 10. GRAVITY 11. ROTATION_VECTOR DEPRECEATED 12. TEMPERATURE 13. ORIENTATION Sensors and location based services 4
- 5. “Sense-ors” on Android A sensor (also called detector) is a device that measures a physical quantity and converts it into a signal which can be read by an observer or by an instrument. 1. ACCELEROMETER 2. GRAVITY MOTION 3. LINEAR_ACCELERATION 4. GYROSCOPE 5. MAGNETIC FIELD POSITION 6. ORIENTATION 7. PROXIMITY 8. ROTATION VECTOR 9. LIGHT 10. BAROMETER ENVIRONMENT 11. AMBIENT TEMPERATURE 12. RELATIVE HUMIDITY 13. TEMPERATURE Sensors and location based services 5
- 6. Sensors in Android applications • Use-cases of sensors in apps: 1. Active-Input 2. Passive-Input Application developer 3. Active-Passive 4. Auto-Rotate Android window manager Sensors and location based services 6
- 7. Sensors in Android applications (1/4) • Active input Sensors and location based services 7
- 8. Sensors in Android applications (2/4) • Passive input Sensors and location based services 8
- 9. Sensors in Android applications (3/4) • Active-passive Sensors and location based services 9
- 10. Sensors in Android applications (4/4) • Auto-rotate Sensors and location based services 10
- 11. Compass : Bearing (Azimuth) 90o 180o Sensors and location based services 11
- 12. Compass : Bearing • iPad as in-flight navigator. Android? • Magnetic north != Geographic North • WiFi / Network provider + Compass = GPS? POSITION (LAT, LONG) + BEARING Sensors and location based services 12
- 13. Compass : Magnetic Declination Sensors and location based services 13
- 14. Accelerometer, Gyroscope : Motion • |Accelerometer| != 9.8 Motion • Initial bearing + rotation of device, POSITION (LAT, LONG) + BEARING + SPEED Sensors and location based services 14
- 15. Barometer : Altitude • Remember this ? “ WiFi / Network provider + Compass = GPS” now how about, “ WiFi / Network provider + Compass + Barometer ” POSITION (LAT, LONG) + BEARING + SPEED + ALTITUDE > GPS Sensors and location based services 15
- 16. nGPS : World Geomagnetic model Sensors and location based services 16
- 17. Using Sensors in your app SensorEvent http://goo.gl/hWOQu SensorManager http://goo.gl/1DRUv Examples : http://goo.gl/AVBDV http://goo.gl/eKq6a Sensors and location based services 17
- 18. Sensor app-dev Tips and tricks Sensor calibration. 1. one-turn deserves another (axes-calib) 2. zero-calib Polling rate fastest/game/ui/normal? Sensor fusion Hard-way Easy-way (Invensense ) http://goo.gl/bHmDe Lessons from WindowOrientationListener.java Android/frameworks/base/core/java/android/view/WindowOrientationListener.java When to register/unregister SensorEventListener When to acquire/release Wakelocks Sensors and location based services 18
- 19. WindowOrientationListener.java Low-pass filter the tilt and orientation angles to avoid "twitchy" behaviour. When the orientation angle reaches a certain threshold, transition These thresholds have some hysteresis built-in to avoid oscillation. Use the magnitude to judge the accuracy of the data. Under ideal conditions, the magnitude should equal to that of gravity. When it differs significantly, we know the device is under external acceleration Use the tilt angle to judge the accuracy of orientation data. When the tilt angle is high in magnitude, we distrust the orientation data. When the device is flat, small physical motion = large changes in orientation angle. Sensors and location based services 19
- 20. App-dev Tips and tricks register sensorEventListener acquire wakelock release wakelock unregister sensorEventListener Sensors and location based services 20
- 21. Thank You!! Questions? android-porting android-developers android-kernel android-platform CONTACT ME Sensors and location based services 21