Retrieving # of satellites used in gps fix from Android

Question

I am trying to retrieve the # of satellites used in the GPS fix. I have implemented two different methods, as shown below:

package ti.utils;

import android.app.Activity;
import android.content.Context;
import android.location.GpsSatellite;
import android.location.GpsStatus;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;

public class Gps {

    private static final int TWO_MINUTES = 1000 * 60 * 2;
    private static Location Location;
    public static int Satellites = -1;

    public static void StartTracking(Activity activity)
    {
        final LocationManager locationManager = (LocationManager) activity.getSystemService(Context.LOCATION_SERVICE);

        //listen for gps status changes.
        GpsStatus.Listener gpsStatusListener = new GpsStatus.Listener() {
            public void onGpsStatusChanged(int event) {
                Log("In onGpsStatusChanged event: " + event);
                if (event == GpsStatus.GPS_EVENT_SATELLITE_STATUS || event == GpsStatus.GPS_EVENT_FIRST_FIX) {
                    GpsStatus status = locationManager.getGpsStatus(null);
                    Iterable<GpsSatellite> sats = status.getSatellites();
                    // Check number of satellites in list to determine fix state
                    Satellites = 0;
                    for (GpsSatellite sat : sats) {
                        //if(sat.usedInFix())
                        Satellites++;
                    }
                    Log("Setting Satellites from GpsStatusListener: " + Satellites);
                }
            }
        };
        locationManager.addGpsStatusListener(gpsStatusListener);

        //listen for location changes.
        LocationListener locationListener = new LocationListener() {
            public void onLocationChanged(Location location) {
                // Called when a new location is found by the network location provider.
                try
                {
                    Log("Location changed! Speed = " + location.getSpeed() + " & Satellites = " + location.getExtras().getInt("satellites"));
                    boolean isBetter = isBetterLocation(location, Location);
                    if(isBetter)
                    {
                        Log("Set to new location");
                        Location = location;
                        Satellites = location.getExtras().getInt("satellites");
                        Log("Setting Satellites from LocationListener: " + Satellites);
                    }
                }
                catch(Exception exc)
                {
                    Log(exc.getMessage());
                }
            }
            public void onStatusChanged(String provider, int status, Bundle extras) {}
            public void onProviderEnabled(String provider) {}
            public void onProviderDisabled(String provider) {}
        };
        locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListener);
    }

    /** Determines whether one Location reading is better than the current Location fix
      * @param location  The new Location that you want to evaluate
      * @param currentBestLocation  The current Location fix, to which you want to compare the new one
      */
    protected static boolean isBetterLocation(Location location, Location currentBestLocation) {
        if (currentBestLocation == null) {
            // A new location is always better than no location
            return true;
        }

        // Check whether the new location fix is newer or older
        long timeDelta = location.getTime() - currentBestLocation.getTime();
        boolean isSignificantlyNewer = timeDelta > TWO_MINUTES;
        boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES;
        boolean isNewer = timeDelta > 0;

        // If it's been more than two minutes since the current location, use the new location
        // because the user has likely moved
        if (isSignificantlyNewer) {
            return true;
        // If the new location is more than two minutes older, it must be worse
        } else if (isSignificantlyOlder) {
            return false;
        }

        // Check whether the new location fix is more or less accurate
        int accuracyDelta = (int) (location.getAccuracy() - currentBestLocation.getAccuracy());
        boolean isLessAccurate = accuracyDelta > 0;
        boolean isMoreAccurate = accuracyDelta < 0;
        boolean isSignificantlyLessAccurate = accuracyDelta > 200;

        // Check if the old and new location are from the same provider
        boolean isFromSameProvider = isSameProvider(location.getProvider(),
                currentBestLocation.getProvider());

        // Determine location quality using a combination of timeliness and accuracy
        if (isMoreAccurate) {
            return true;
        } else if (isNewer && !isLessAccurate) {
            return true;
        } else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) {
            return true;
        }
        return false;
    }

    /** Checks whether two providers are the same */
    private static boolean isSameProvider(String provider1, String provider2) {
        if (provider1 == null) {
          return provider2 == null;
        }
        return provider1.equals(provider2);
    }

    private static void Log(String message) {
        if(message != null && message.length() > 0) {
            //android.util.Log.i(LCAT, message);
            org.appcelerator.kroll.common.Log.i("SygicModule", message);
        }
    }

}

Neither of the listener events (onGpsStatusChanged & onLocationChanged) ever fire, even though I have standalone GPS enabled on my phone. I have the ACCESS_FINE_LOCATION permission set:

<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>

I downloaded a 3rd party app called GPS Status and it was able to correctly display the # of satellites, so I know it isn't an issue with my Droid X2.

Any ideas?

Answer 1

locationManager.requestLocationUpdates(LocationManager.NETWORK_PROVIDER, 0, 0, locationListener);

Should be

locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);

Answer 2

Here is the code that ended up working.

package ti.utils;

import android.app.Activity;
import android.content.Context;
import android.location.GpsSatellite;
import android.location.GpsStatus;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.Bundle;

public class Gps {

    private static final int TWO_MINUTES = 1000 * 60 * 2;
    private static Location Location;
    public static int Satellites = -1;

    public static void StartTracking(Activity activity)
    {
        final LocationManager locationManager = (LocationManager) activity.getSystemService(Context.LOCATION_SERVICE);

        //listen for gps status changes.
        GpsStatus.Listener gpsStatusListener = new GpsStatus.Listener() {
            @Override
            public void onGpsStatusChanged(int event) {
                Log("In onGpsStatusChanged event: " + event);
                if (event == GpsStatus.GPS_EVENT_SATELLITE_STATUS || event == GpsStatus.GPS_EVENT_FIRST_FIX) {
                    GpsStatus status = locationManager.getGpsStatus(null);
                    Iterable<GpsSatellite> sats = status.getSatellites();
                    // Check number of satellites in list to determine fix state
                    Satellites = 0;
                    for (GpsSatellite sat : sats) {
                        //if(sat.usedInFix())
                        Satellites++;
                    }
                    Log("Setting Satellites from GpsStatusListener: " + Satellites);
                }
            }
        };
        locationManager.addGpsStatusListener(gpsStatusListener);

        //listen for location changes.
        LocationListener locationListener = new LocationListener() {
            @Override
            public void onLocationChanged(Location location) {
                // Called when a new location is found by the network location provider.
                /*try
                {
                    Log("Location changed! Speed = " + location.getSpeed() + " & Satellites = " + location.getExtras().getInt("satellites"));
                    boolean isBetter = isBetterLocation(location, Location);
                    if(isBetter)
                    {
                        Log("Set to new location");
                        Location = location;
                        Satellites = location.getExtras().getInt("satellites");
                        Log("Setting Satellites from LocationListener: " + Satellites);
                    }
                }
                catch(Exception exc)
                {
                    Log(exc.getMessage());
                }*/
            }
            public void onStatusChanged(String provider, int status, Bundle extras) {}
            public void onProviderEnabled(String provider) {}
            public void onProviderDisabled(String provider) {}
        };
        locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, locationListener);
    }

    /** Determines whether one Location reading is better than the current Location fix
      * @param location  The new Location that you want to evaluate
      * @param currentBestLocation  The current Location fix, to which you want to compare the new one
      */
    protected static boolean isBetterLocation(Location location, Location currentBestLocation) {
        if (currentBestLocation == null) {
            // A new location is always better than no location
            return true;
        }

        // Check whether the new location fix is newer or older
        long timeDelta = location.getTime() - currentBestLocation.getTime();
        boolean isSignificantlyNewer = timeDelta > TWO_MINUTES;
        boolean isSignificantlyOlder = timeDelta < -TWO_MINUTES;
        boolean isNewer = timeDelta > 0;

        // If it's been more than two minutes since the current location, use the new location
        // because the user has likely moved
        if (isSignificantlyNewer) {
            return true;
        // If the new location is more than two minutes older, it must be worse
        } else if (isSignificantlyOlder) {
            return false;
        }

        // Check whether the new location fix is more or less accurate
        int accuracyDelta = (int) (location.getAccuracy() - currentBestLocation.getAccuracy());
        boolean isLessAccurate = accuracyDelta > 0;
        boolean isMoreAccurate = accuracyDelta < 0;
        boolean isSignificantlyLessAccurate = accuracyDelta > 200;

        // Check if the old and new location are from the same provider
        boolean isFromSameProvider = isSameProvider(location.getProvider(),
                currentBestLocation.getProvider());

        // Determine location quality using a combination of timeliness and accuracy
        if (isMoreAccurate) {
            return true;
        } else if (isNewer && !isLessAccurate) {
            return true;
        } else if (isNewer && !isSignificantlyLessAccurate && isFromSameProvider) {
            return true;
        }
        return false;
    }

    /** Checks whether two providers are the same */
    private static boolean isSameProvider(String provider1, String provider2) {
        if (provider1 == null) {
          return provider2 == null;
        }
        return provider1.equals(provider2);
    }

    private static void Log(String message) {
        if(message != null && message.length() > 0) {
            //android.util.Log.i(LCAT, message);
            org.appcelerator.kroll.common.Log.i("UtilsModule", message);
        }
    }

}

Answer 3

If you can't get the numebr of satellites through GPS_EVENT_SATELLITE_STATUS then you could have your activity implement NmeaListener.

If you implement the NmeaListener then you will have to parse the message string received in onNmeaReceived in order to extract the number of satellites. The NMEA formats are described here. Then you might like to do a Google search for "Java" + "NMEA parser"

Answer 4

I got it working by having following in code. locationManager.requestLocationUpdates(LocationManager.GPS_PROVIDER, 0, 0, new LocationUpdateHandler()); int nSatellites = location.getExtras().getInt("satellites", -1);

nSatellites was found to be >0 once i started getting fix(onLocationChanged callbacks) .