Re: [android-developers] Re: GPS accuracy reliability
Hi jgostylo, On 07/15/2010 07:01 AM, jgostylo wrote: All of this and people have only sort of answered my question. I understand that the answer may just be I don't really know what it would do and I understand that really isn't an answer people post on the forum because it does not fill the information gap. The accuracy is a function of the number of satellites in view and other stuff. I get that. But the question remains the same. When it tells me my location is hundreds of miles from where I actually am, will the call to getAccuracy return hundreds of thousands of meters? I don't know if what I've noted is of any help at all, but here we go anyway: It is easy to get confused when mixing network(coarse) and gps(fine) providers if you just listen to both. For network I've seen it be radically off many times (presumably the operator has messed up IDs and positions), but at least it is usually quick to report SOMETHING. When it comes to gps I would say that the the blue circle shown on Google Map quite often would have to be twice as big for the first few samples (with pretty bad accuracy) to show the truth, but when it comes down to two digit meters it usually is quite good for me - even when I'm indoors (reasonably low buildings). Compared to the iPhone3GS that my colleagues use, it is significantly better actually. This might just be luck with my particular devices, though. So basically, to be on the safe side, I'd say double the number of meters you get from accuracy. The other thing that you will need to consider is to have a best before timestamp on all positions. In some cases I've had a pretty good position from the GPS for a long time when for some reason it drops the signal and you need to go back to network until it comes back. If you are moving fast (say sitting on a train with iffy net coverage too) this can get pretty strange results if you trust your old data for too long. (Your currentLocationAccuracy variable may be trying to address this?) Obviously, debugging this is hard and potentially expensive (even dangerous if you drive yourself!). Disclaimer: I don't claim to be an expert on this, this above is just based on my own observations. / Jonas -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: GPS accuracy reliability
drpickett:
When I say I demand a certain accuracy from the GPS what I mean is
that when it reports a location I call getAccuracy and if it is not
good enough I throw away the result. Maybe I should just be more
lenient on the accuracy from a network location.
All of this and people have only sort of answered my question. I
understand that the answer may just be I don't really know what it
would do and I understand that really isn't an answer people post on
the forum because it does not fill the information gap. The accuracy
is a function of the number of satellites in view and other stuff. I
get that. But the question remains the same. When it tells me my
location is hundreds of miles from where I actually am, will the call
to getAccuracy return hundreds of thousands of meters?
PsuedoCode for the previous request (may be missing and spotty but you
get the gist):
public class ContainerClass extends Activity
onCreate(Bundle savedInstanceState)
{
...
lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
Criteria myCriteria = new Criteria();
myCriteria.setAccuracy(Criteria.ACCURACY_FINE);
providerList = lm.getProviders(true);
for (String provider : providerList)
{
if (provider.equals(LocationManager.GPS_PROVIDER))
{
lm.requestLocationUpdates(provider, 7000, 20, gpsLocationListener);
}
else if (provider.equals(LocationManager.NETWORK_PROVIDER))
{
lm.requestLocationUpdates(provider, 7000, 20,
networkLocationListener);
}
}
}
// Wireless location listener
private final LocationListener networkLocationListener = new
LocationListener() {
public void onLocationChanged(Location location) {
ContainerClass.this.gpsLocationListener.onLocationChanged(location);
}
public void onProviderDisabled(String provider){}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status, Bundle
extras) {}
};
// GPS location listener
private final LocationListener gpsLocationListener = new
LocationListener() {
public void onLocationChanged(Location location) {
//location.getProvider() will return which provider
supplied this location
//Logic when a location is found
if ((long)Math.floor(SystemClock.elapsedRealtime()/1000) -
locationTimeElapse 7)
{
locationTimeElapse =
(long)Math.floor(SystemClock.elapsedRealtime()/1000);
currentLocationAccuracy += 10;
if (locationAccuracy 1500f)
{
currentLocationAccuracy = 1500f;
}
}
if (location.getAccuracy() 30.0 || location.getAccuracy() =
currentLocationAccuracy)
{
currentLocationAccuracy = location.getAccuracy();
//and other junk happens
}
}
public void onProviderDisabled(String provider){}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status, Bundle
extras) {}
};
On Jul 10, 9:13 pm, drpickett davidrpick...@gmail.com wrote:
Maybe I
can be choosy and say that if it GPS then I demand 20 meter accuracy
but if it is network then I only demand 500 meter???
Chuck Norris can demand a certain accuracy from GPS - You can't -
GPS reports its accuracy to you - It is a function of the number of
satellites in view, and other stuff
dp
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Re: [android-developers] Re: GPS accuracy reliability
-- When it tells me my location is hundreds of miles from where I actually
am, will the call
-- to getAccuracy return hundreds of thousands of meters?
With my experience, sometimes I got a accuracy
of 10M, actually 100m away from where I was.
On Thu, Jul 15, 2010 at 1:01 PM, jgostylo jgost...@gmail.com wrote:
drpickett:
When I say I demand a certain accuracy from the GPS what I mean is
that when it reports a location I call getAccuracy and if it is not
good enough I throw away the result. Maybe I should just be more
lenient on the accuracy from a network location.
All of this and people have only sort of answered my question. I
understand that the answer may just be I don't really know what it
would do and I understand that really isn't an answer people post on
the forum because it does not fill the information gap. The accuracy
is a function of the number of satellites in view and other stuff. I
get that. But the question remains the same. When it tells me my
location is hundreds of miles from where I actually am, will the call
to getAccuracy return hundreds of thousands of meters?
PsuedoCode for the previous request (may be missing and spotty but you
get the gist):
public class ContainerClass extends Activity
onCreate(Bundle savedInstanceState)
{
...
lm = (LocationManager)getSystemService(Context.LOCATION_SERVICE);
Criteria myCriteria = new Criteria();
myCriteria.setAccuracy(Criteria.ACCURACY_FINE);
providerList = lm.getProviders(true);
for (String provider : providerList)
{
if (provider.equals(LocationManager.GPS_PROVIDER))
{
lm.requestLocationUpdates(provider, 7000, 20, gpsLocationListener);
}
else if (provider.equals(LocationManager.NETWORK_PROVIDER))
{
lm.requestLocationUpdates(provider, 7000, 20,
networkLocationListener);
}
}
}
// Wireless location listener
private final LocationListener networkLocationListener = new
LocationListener() {
public void onLocationChanged(Location location) {
ContainerClass.this.gpsLocationListener.onLocationChanged(location);
}
public void onProviderDisabled(String provider){}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status, Bundle
extras) {}
};
// GPS location listener
private final LocationListener gpsLocationListener = new
LocationListener() {
public void onLocationChanged(Location location) {
//location.getProvider() will return which provider
supplied this location
//Logic when a location is found
if ((long)Math.floor(SystemClock.elapsedRealtime()/1000) -
locationTimeElapse 7)
{
locationTimeElapse =
(long)Math.floor(SystemClock.elapsedRealtime()/1000);
currentLocationAccuracy += 10;
if (locationAccuracy 1500f)
{
currentLocationAccuracy = 1500f;
}
}
if (location.getAccuracy() 30.0 || location.getAccuracy() =
currentLocationAccuracy)
{
currentLocationAccuracy = location.getAccuracy();
//and other junk happens
}
}
public void onProviderDisabled(String provider){}
public void onProviderEnabled(String provider) {}
public void onStatusChanged(String provider, int status, Bundle
extras) {}
};
On Jul 10, 9:13 pm, drpickett davidrpick...@gmail.com wrote:
Maybe I
can be choosy and say that if it GPS then I demand 20 meter accuracy
but if it is network then I only demand 500 meter???
Chuck Norris can demand a certain accuracy from GPS - You can't -
GPS reports its accuracy to you - It is a function of the number of
satellites in view, and other stuff
dp
--
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[android-developers] Re: GPS accuracy reliability
Hi! Could you provide some sample code for verifying which they are getting results from (gps vs. Network)? Thanks so much! On Jul 10, 11:07 am, jgostylo jgost...@gmail.com wrote: In answer to some questions. I am setting up the network location finder and theGPSlocation finder using 2 separate LocationListeners. I have some logic that determines what the user has activated so I only listen togpsif the havegpsenabled and so forth. From my user feedback it seems like the biggest location discrepancies happen withGPS. I have not been able to personally verify this. I don't need to be super picky about how accurate it is (500 meters would suffice). I am just wondering ifGPSis putting people several hundred miles away from their actual location is it also reliable to say that its accuracy is over 200,000 meters? That way I can throw out anything that says it is less accurate than 500 meters. If it is putting my user 200 miles away and saying that it thinks its accuracy is within 100 meter then it really does me no good. Maybe I can be choosy and say that if itGPSthen I demand 20 meter accuracy but if it is network then I only demand 500 meter??? Thanks for the responses. On Jul 10, 10:19 am, Maps.Huge.Info (Maps API Guru) cor...@gmail.com wrote: You can manage the orientation changes yourself and eliminate this source of device confusion, it's quite easy, just add android:configChanges=orientation to your manifest's activity. As for the signal source, just make sure to check your provider for gps - if it saysgps, it will be from that source. -John Coryat -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: GPS accuracy reliability
Maybe I can be choosy and say that if it GPS then I demand 20 meter accuracy but if it is network then I only demand 500 meter??? Chuck Norris can demand a certain accuracy from GPS - You can't - GPS reports its accuracy to you - It is a function of the number of satellites in view, and other stuff dp -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: GPS accuracy reliability
2) in the backend applcation - Trains travel on tracks (hopefully) so ignore all GPS positions that we cannot map on to a track. Oh I'm highly jealous, wish I could filter on tracks as well. Pent -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: GPS accuracy reliability
Get enough data sets and you know where the tracks are :) On Jul 10, 12:15 pm, Pent lee.wil...@googlemail.com wrote: 2) in the backend applcation - Trains travel on tracks (hopefully) so ignore all GPS positions that we cannot map on to a track. Oh I'm highly jealous, wish I could filter on tracks as well. Pent -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: GPS accuracy reliability
That was my thought. Unless location provider registration is managed through the variety of app lifecycle state changes, it is easy to put an app in a state where it acquires the device location using Network based location providers, even though the user selected GPS and unselected everything else (Namely, Use wireless networks:). The downside of unregistering and registering location providers with every lifecycle state change (i.e. in onPause(), onResume() and so forth) is when users manically switch device orientation back and forth. This leads to a series of lifecycle breakdown and restart calls that seem to have the potential of getting Android location provider registration confused. If you haven't done already, I'd recommend to experiment with this for a few hours to get a feel how it all plays out in relation to your apps. On Jul 9, 7:50 am, Maps.Huge.Info (Maps API Guru) cor...@gmail.com wrote: Question: How are you getting your location fix? Are you using ACCURACY_FINE and assuming it will use the GPS? Unless you specifically test for the provider being GPS, it might default to network, which would give you a position with limited accuracy. I've seen this bouncing around effect when the wireless location (network) provider is trying to figure out where the device is, as it zeros in on the location, it can hop all over the map. Bottom line: Don't assume that ACCURACY_FINE will be GPS, unless you have GPS satellites in view and the user has enabled GPS, you'll be using the network location service instead. -John Coryat -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: GPS accuracy reliability
You can manage the orientation changes yourself and eliminate this source of device confusion, it's quite easy, just add android:configChanges=orientation to your manifest's activity. As for the signal source, just make sure to check your provider for gps - if it says gps, it will be from that source. -John Coryat -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: GPS accuracy reliability
In answer to some questions. I am setting up the network location finder and the GPS location finder using 2 separate LocationListeners. I have some logic that determines what the user has activated so I only listen to gps if the have gps enabled and so forth. From my user feedback it seems like the biggest location discrepancies happen with GPS. I have not been able to personally verify this. I don't need to be super picky about how accurate it is (500 meters would suffice). I am just wondering if GPS is putting people several hundred miles away from their actual location is it also reliable to say that its accuracy is over 200,000 meters? That way I can throw out anything that says it is less accurate than 500 meters. If it is putting my user 200 miles away and saying that it thinks its accuracy is within 100 meter then it really does me no good. Maybe I can be choosy and say that if it GPS then I demand 20 meter accuracy but if it is network then I only demand 500 meter??? Thanks for the responses. On Jul 10, 10:19 am, Maps.Huge.Info (Maps API Guru) cor...@gmail.com wrote: You can manage the orientation changes yourself and eliminate this source of device confusion, it's quite easy, just add android:configChanges=orientation to your manifest's activity. As for the signal source, just make sure to check your provider for gps - if it says gps, it will be from that source. -John Coryat -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: GPS accuracy reliability
I have had the same reports from my user community within my GPS application for Android. In my support emails I have been telling them that it is most likely a hardware/OS issue, and a hard reset (battery pull) should fix it. I have had a few users reply back and said that has fixed it. I think this may be a issue with the API that is is providing use the wrong information when we request it. In my eyes I see this as a bug with Android if it provides the wrong information once we request it. Justin On Jul 9, 8:48 am, jgostylo jgost...@gmail.com wrote: This is a general question about GPS accuracy reporting based on feedback from my user community. My app has an issue where many players get bounced all over kingdom come when using GPS to get a signal. I had this issue with my G1 on occasion but not on my Nexus One. I am talking hundreds of miles from their real location. I changed the code to throw out anything that was not at least 500 meters accurate. My question is, if the location placement is hundreds of miles off, how reliable will the accuracy reporting be? Does it realize that it could be hundreds of miles off? I am asking the community because I cannot reproduce the scenario with what I currently have so I can't test if my fix is meaningful. Does GPS know when its readings are that far off? -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: GPS accuracy reliability
Question: How are you getting your location fix? Are you using ACCURACY_FINE and assuming it will use the GPS? Unless you specifically test for the provider being GPS, it might default to network, which would give you a position with limited accuracy. I've seen this bouncing around effect when the wireless location (network) provider is trying to figure out where the device is, as it zeros in on the location, it can hop all over the map. Bottom line: Don't assume that ACCURACY_FINE will be GPS, unless you have GPS satellites in view and the user has enabled GPS, you'll be using the network location service instead. -John Coryat -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
[android-developers] Re: GPS accuracy reliability
A GPS fix can be inaccurate - no matter how confident the GPS device is :) My experience here is from GPS units mounted on multiple trains travelling about the UK, recording their position every few seconds. A small percentage of the values we recieved from the GPS units were completly un-trustworthy (ie. the train would have had to do over 200mph to get between the last fix and the current positon). For a similar small percentage the train was NOT on a track! We realised we had to sanitise the data returned from the GPS units. We did this at 2 levels: 1) on the Train - no point processing (storing) a GPS position when the calcuated speed (NOT the speed from the GPS unit but calculated by us from the previous good fix) was totally unreasonable. 2) in the backend applcation - Trains travel on tracks (hopefully) so ignore all GPS positions that we cannot map on to a track. Conslusion - a single GPS position should NOT be used at the application level unless it makes sense - for a given value of sanity :) /Richard On Jul 9, 3:50 pm, Maps.Huge.Info (Maps API Guru) cor...@gmail.com wrote: Question: How are you getting your location fix? Are you using ACCURACY_FINE and assuming it will use the GPS? Unless you specifically test for the provider being GPS, it might default to network, which would give you a position with limited accuracy. I've seen this bouncing around effect when the wireless location (network) provider is trying to figure out where the device is, as it zeros in on the location, it can hop all over the map. Bottom line: Don't assume that ACCURACY_FINE will be GPS, unless you have GPS satellites in view and the user has enabled GPS, you'll be using the network location service instead. -John Coryat -- You received this message because you are subscribed to the Google Groups Android Developers group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
