PS just to clarify point 2: the GPS location listener is running in the background while the user is waiting, so it's getting a fix *before* the user clicks on the report button.
The question is why this fix is so much better than the fix over the same period when the background thread is running. On Jul 16, 10:09 pm, Anna PS <[email protected]> wrote: > Hi there, > > I'm having a weird problem with GPS accuracy. > > Basically, I check the GPS accuracy in a background thread after the > user clicks a report button, and show the accuracy in a progress > dialog, changing second by second. (Code is below.) The following > strange thing happens: > > 1. If the user clicks more or less immediately on the button after > taking the phone out, accuracy is unsurprisingly pretty poor to start > off with, say more than 100m. But the accuracy never really improves > very much while the user is running the background thread. There is > some improvement, but it's slow and it never gets very accurate. > 2. However, if the user gets the phone out and then waits for several > seconds *without* clicking on the button and running the background > thread, and *then* clicks on the button, the accuracy quickly improves > and becomes very good. When they click on the button, the accuracy > shows up as fine - within the same length of time. > > So it looks as though running the background thread makes the GPS > worse. Why on earth would this happen? > > This is a problem for me because my app involves sending GPS location > info off to a network service, and I check for a minimum accuracy on > the client side. Many of my users are reporting that they can't get a > GPS fix that's accurate enough. They can't get a fix that's within > tens of metres from my app even when other GPS monitoring applications > are reporting accuracy of just a few metres! > > Basically my question is this - does the fact that I'm running a > background thread somehow make the accuracy worse? Or is the problem > in my code, something to do with the way that I'm polling the GPS > data? > > Any thoughts very much appreciated. > > Thanks > Anna > > ----------- > > public class Home extends Activity { > // **************************************************** > // Local variables > // **************************************************** > private static final String LOG_TAG = "Home"; > private Button btnReport; > > // Location info > LocationManager locationmanager = null; > LocationListener listener; > Location location; > private Double latitude; > private Double longitude; > private String latString = ""; > private String longString = ""; > private static int globalStatus = 13; > private static final int SUCCESS = 0; > private static final int LOCATION_NOT_FOUND = 1; > private static final int LOCATION_NOT_ACCURATE = 2; > // Dialog and thread handling > private ProgressDialog pd2; > private int mSeconds = 100; > private int mProgressStatus = 300; > private Handler nHandler = new Handler(); > final Runnable nUpdateResults = new Runnable() { > public void run() { > pd2.dismiss(); > if (globalStatus == LOCATION_NOT_ACCURATE) { > //warn user here > } else if (globalStatus == LOCATION_NOT_FOUND) { > //warn user here > } else { > uploadToService(); > } > } > }; > > // Called when the activity is first created > @Override > public void onCreate(Bundle icicle) { > super.onCreate(icicle); > setContentView(R.layout.home); > btnReport = (Button) findViewById(R.id.report_button); > testProviders(); > setListeners(); > } > > // Register GPS location listener etc - called when activity first > created > public void testProviders() { > // Log.e(LOG_TAG, "testProviders"); > // Register for location listener > String location_context = Context.LOCATION_SERVICE; > locationmanager = (LocationManager) getSystemService > (location_context); > listener = new LocationListener() { > public void onLocationChanged(Location location) { > } > > public void onProviderDisabled(String provider) { > } > > public void onProviderEnabled(String provider) { > } > > public void onStatusChanged(String provider, int > status, > Bundle extras) { > } > }; > > locationmanager.requestLocationUpdates(LocationManager.GPS_PROVIDER, > 0, > 0, listener); > if (!locationmanager.isProviderEnabled > (LocationManager.GPS_PROVIDER)) { > //warn user > } > } > > // When the user clicks the report button, bring up a progress dialog > showing GPS accuracy > private void setListeners() { > btnReport.setOnClickListener(new OnClickListener() { > public void onClick(View v) { > > pd2 = ProgressDialog.show(Home.this, "Looking > for GPS fix...", > "Looking for a GPS fix", > true, false); > Thread t = new Thread() { > public void run() { > while ((mProgressStatus > 24) > || (mSeconds > 15)) { > mProgressStatus = > (int) getGPSFix(); > // Update the > progress bar > nHandler.post(new > Runnable() { > public void > run() { > pd2 > > .setTitle("Looking for GPS fix: accuracy now " > > + mProgressStatus + "m"); > pd2 > > .setMessage("Looking for GPS fix: we ask for minimum 24m > accuracy, phone says last fix was approx " > > + (mSeconds + 10) > > + " seconds ago with accuracy " > > + mProgressStatus > > + "m. Please make sure you can see the sky."); > } > }); > } > if ((mProgressStatus > 24) || > (mSeconds > 15)) { > globalStatus = > LOCATION_NOT_ACCURATE; > } > nHandler.post(nUpdateResults); > } > }; > t.start(); > } > }); > } > > // Get the current GPS accuracy found by the locationmanager, return > -1 if can't be found > private float getGPSFix() { > Log.d(LOG_TAG, "getGPSFix"); > > if (!(locationmanager == null)) { > location = locationmanager > > .getLastKnownLocation(LocationManager.GPS_PROVIDER); > } > > if (location != null) { > // TODO - put back in > long currentTime = System.currentTimeMillis(); > long gpsTime = location.getTime(); > Log.d(LOG_TAG, "gpsTime = " + gpsTime + ", > currentTime = " > + currentTime); > long timeDiffSecs = (currentTime - gpsTime) / 1000; > mSeconds = (int) timeDiffSecs; > Log.d(LOG_TAG, "timeDiffSecs = " + timeDiffSecs + ", > mSeconds = " > + mSeconds); > latitude = location.getLatitude(); > longitude = location.getLongitude(); > latString = latitude.toString(); > longString = longitude.toString(); > Log.d(LOG_TAG, "accuracy = " + > location.getAccuracy()); > return location.getAccuracy(); > } else { > return -1; > } > } > > > > } --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Android Developers" group. 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