Android Open Source - yousense-android-tracker Gps History

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License

The source code is released under:

Energy-efficent motion and location tracker for Android. Based on Mattias's power and tracking work. I plan to release it as GPL, once I have a paper published that goes with it. Might also release i...

Java Source Code

package com.linnap.locationtracker.gps;
// ww  w  . jav  a  2  s  . c om
import java.util.ArrayDeque;

import android.location.Location;

import com.linnap.locationtracker.LocationTrackerService;
import com.linnap.locationtracker.SensorConfig;

public class GpsHistory {

  LocationTrackerService service;
  ArrayDeque<Location> history;
  
  public GpsHistory(LocationTrackerService service) {
    this.service = service;
    this.history = new ArrayDeque<Location>(SensorConfig.GPS_HISTORY_SIZE);
  }
  
  public synchronized void clear() {
    history.clear();
  }
  
  public synchronized void addFix(Location latest) {
    // Add fix to history.
    if (history.size() >= SensorConfig.GPS_HISTORY_SIZE)
      history.removeLast();
    
    history.addFirst(withValidSpeed(latest));
  }

  /**
   * Assumes GPS is tracking at low speed.
   */
  public synchronized boolean shouldSwitchToHighSpeed() {
    // If there is no history yet, should not do any switching.
    if (history.isEmpty()) {
      service.log("No history, perhaps still slow.");
      return false;
    }
    
    // Switch immediately if phone is moving fast.
    float speed = history.getFirst().getSpeed();
    if (speed > SensorConfig.GPS_SWITCH_SPEED_THRESHOLD) {
      service.log(String.format("Latest speed %.3f, go to fast.", speed));
      return true;
    } else {
      service.log(String.format("Latest speed %.3f, still slow.", speed));
      return false;
    }
  }

  /**
   * Assumes GPS is tracking at high speed.
   */
  public synchronized boolean shouldSwitchToLowSpeed() {
    // If history is too short to make a decision, should not do any switching.
    if (history.size() < SensorConfig.GPS_HIGHTOLOW_SPEEDS_CONSIDERED) {
      service.log(String.format("History %d, perhaps still fast.", history.size()));
      return false;
    }

    float maxSpeed = Float.NEGATIVE_INFINITY;
    for (Location loc : history)
      if (loc.getSpeed() > maxSpeed)
        maxSpeed = loc.getSpeed();
        
    if (maxSpeed < SensorConfig.GPS_SWITCH_SPEED_THRESHOLD) {
      service.log(String.format("Max speed %.3f, go to slow.", maxSpeed));
      return true;
    } else {
      service.log(String.format("Max speed %.3f, still fast.", maxSpeed));
      return false;
    }
  }
  
  /**
   * Assumes GPS is tracking at low speed.
   */
  public synchronized boolean shouldReportStationary() {
    // If history is too short to make a decision, should not do any switching.
    if (history.size() < SensorConfig.GPS_LOWTOOFF_DISTANCES_CONSIDERED)
      return false;
    
    float maxDistance = Float.NEGATIVE_INFINITY;
    Location latest = history.getFirst();
    for (Location historical : history) {
      float distance = latest.distanceTo(historical);
      
      if (distance > maxDistance)
        maxDistance = distance;
      
      if (maxDistance > SensorConfig.GPS_STATIONARY_DISTANCE_THRESHOLD) {
        service.log(String.format("Distance %.3f found, out of stationary bounds.", maxDistance));
        // Return false early, avoid computing all distances.
        return false;
      }
    }
    
    service.log(String.format("Max distance %.3f, stationary.", maxDistance));
    return true;
  }
  
  private Location withValidSpeed(Location location) {
    if (location.hasSpeed()) {
      if (location.getSpeed() >= 0.0f && location.getSpeed() < SensorConfig.GPS_MAX_VALID_SPEED)        
        return location;  // Speed from fix is valid.
      else
        service.log(String.format("Fix has invalid speed: %.4f", location.getSpeed()));
    } else {
      service.log("Fix has no speed");
    }
    
    // Speed is missing or messed up. Computing between last points, if possible.
    Location valid = new Location(location);
    if (history.isEmpty()) {
      valid.setSpeed(0.0f);
    } else {
      Location last = history.getFirst();
      float distance = location.distanceTo(last);
      float seconds = (location.getTime() - last.getTime()) / 1000.0f;
      if (distance >= 0.0f && seconds > 0.0f) {
        valid.setSpeed(distance / seconds);
      } else {
        service.log(String.format("Cannot compute speed with distance %.3f m and %.3f sec", distance, seconds));
        valid.setSpeed(0.0f);
      }
    }
    return valid;
  }
}

Java Source Code List

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