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Hi i have weird problem with my GPS.
While I driving (car is moving) everything is beauty and sweet but once I stop my car my GPS is still moving for about 10 sometimes 20 sec showing 2km/h then 0km/h then 2km/h again. Sometimes when I stop car on junction my Gps will jump on the perpendicular road and from time to time my arrow on the map just turn around to opposite direction and the maps sets a new route! Once i move my car everything going back to normal.
I was using first my TomTom and i just thought it`s a map problem although i haven`t problem with that on my Rhodium either X1. So I decided to try Igo8 and it`s exactly this same. Even on the roundabout my gps can jump somewhere else on different road.
I tried all Radios available for HD2, many Roms and just have no idea what more I can do. Many people on HD2 forum in Poland have this same problem.
I also tried GPS fix cab downloaded here from xda but no luck its ever worst.
I can add that i'm getting GPS fix in few second so its good the problem is just my gps is moving around.
PS. Very, very rarely have no problem with this jumpin gps around. But is like 1/30.
Do you have access to an external Bluetooth GPS receiver you can test out? That could eliminate or isolate some possibilities.
balane said:
Do you have access to an external Bluetooth GPS receiver you can test out? That could eliminate or isolate some possibilities.
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unfortunately i don`t. but on my Touch Pro 2 and Xperia never had this problem.
hi,
are you using the 'gpsmoddriver' software, that is floating around here in the forum?. its made for using the compass data when no gps fix is available. it causes such failures in igo and copilot on my hd2. after uninstalling it gps works much more percise to me, when im not moving.
regards mad
Happens with mine as well. I have replaced my HD2 and it seems that the 2nd unit acts the same. tried various ROMs/RADIOs (official/cooked) - nothing seemed to fix this.
It's quite funny though... most of the people rather paying attention to the fix time instead of the accuracy (which is quite bad imo) in addition to this weird phenomenon. I doubt that the AGPS is somehow related, but it will be nice to know how to disable this feature, and try to acquire the signal without it. maybe this is the cause.
Btw, check this out - http://forum.xda-developers.com/showthread.php?t=600232
Fatherboard said:
Happens with mine as well. I have replaced my HD2 and it seems that the 2nd unit acts the same. tried various ROMs/RADIOs (official/cooked) - nothing seemed to fix this.
It's quite funny though... most of the people rather paying attention to the fix time instead of the accuracy (which is quite bad imo) in addition to this weird phenomenon. I doubt that the AGPS is somehow related, but it will be nice to know how to disable this feature, and try to acquire the signal without it. maybe this is the cause.
Btw, check this out - http://forum.xda-developers.com/showthread.php?t=600232
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Agps - this feature is available in NRGZ roms. I tried to turn on and off and it was no different.
PS. thanks for answering.
madbird said:
hi,
are you using the 'gpsmoddriver' software, that is floating around here in the forum?. its made for using the compass data when no gps fix is available. it causes such failures in igo and copilot on my hd2. after uninstalling it gps works much more percise to me, when im not moving.
regards mad
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As i said before : i was using it. I had feelings its jumping around the places more than without it so I uninstalled it.
Tried to email HTC regarding this. they claim that their HD2's don't exhibit this behavior, even though I've tried two different units, from different batches.
I don't know what to do... this drives IGO nuts - it causes igo to switch lanes, directions and having the route recalculated without any good reason.
Fatherboard said:
Tried to email HTC regarding this. they claim that their HD2's don't exhibit this behavior, even though I've tried two different units, from different batches.
I don't know what to do... this drives IGO nuts - it causes igo to switch lanes, directions and having the route recalculated without any good reason.
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Sometimes its just pointless to talk with those dickheads.
They ll never say true.
With pink camera was this same. They were saying at the beginning that they have no problem with pink spot at all. And what was next? We need just more people to email or ring them.
Most of them even not using HD2. They've seen for few minutes and think they'll know everything about it.
It was so many bugs with this device they just dont want to hear about another one!
In addition to that, both of my units tended to show different position and altitude readings each time i powered up igo or google maps. while exhibiting the differences I obviously didn't from my current position, not even an inch.
to try to make things clearer. that's what I did :
loading igo -> acquiring signal within seconds -> getting a certain position reading with altitude of 11 meters (for example) -> quit -> reloading igo -> acquiring signal within seconds -> slightly different position, altitude of 75 meters or a negative value (for example).
even the small blinking dot in igo (which determines the actual gps mark) doesn't fit to my physical location on the road which I'm currently driving on. it sometimes blinks few meters to the right/left, and sometimes it tracks behind the guidance arrow (as it should be).
Could be
Simply a limitation of GPS. I have seen it on other GPS's. Garmin etrex. Try walking with one and even thou you are walking in a straight line it plots a zigzag path. More satelites (10+) should reduce this issue.
Basically the GPS is only accurate to a certain range from +-50m to +- 2 meters depending on the no of sats. The location is detemined by timing from when the signal was sent to when it was received. Calcs how far away the sat is (Speed of light??). It is possible you care getting a fluctuation in your current location. Eg
Sample 1 says you are point a.
Sample 2 says you are 2 meters to the right.
Sample 3 says you are 2 meters to the left.
Still in the +- 5 meters but the gps is plotting you moving backwards and forwards.
Guys, it is a problem everyone has, gps position is not as accurate or stable on the hd2 as on most other htc devices. And with an erratic gps position automatically comes an erratic speed. Don't know yet if it is because of a different gps module that's inside the hd2 or because of the inclusion of crappy gps drivers. Will try to find out soon....
Anyway, gpsmoddriver is not the cause of this problem since the problem is also on an hd2 without having gpsmoddriver installed. Because of the functionality of gpsmoddriver to improve the gps readings, in some cases it can amplify your erratic gps position, and that is also what some of you have been experiencing. Remember you can always use gpsmoddriver to add the hardware compass functionality to your navigation software, while additionally configuring gpsmoddriver to leave gps data untouched so it won't make the erratic position and speed worse. For more info or help, please visit the gpsmoddriver thread: http://forum.xda-developers.com/showthread.php?t=571266
EDIT: Of course the HD2 has a new snapdragon chip which has built-in GPS just like many previous generations of phones. Most likely qualcomm changed the way gps works in their new line of Snapdragon processors...
The movement of vehicles around you or even the movement of the sun's rays on buildings nearby can distort GPS signals. The GPS navigator software tries to rationalize this distortion and that usually appears as a movement when you are still. On the other hand, if you drive into a tunnel using TomTom and some other software, you will often see yourself driving straight on in the tunnel well after the GPS is receiving no more satellite signals.
In top-of-the-line built-in navigation systems, the GPS data is supplemented by inertial guidance. (Someone could create a similar supplement for the HD2 The supplementary information allows the system to reconcile the GPS information with information on your car's actual movement.
But for us mere mortals, we just have to live with it.
Well... this particular gps chip is quite useless, then. if my navigation program has to recalculate the route each time I stop at traffic light, then it seems that I either have to purchase a usb-based gps to pair with the HD2, or replace this device. I counted on it to perform well.
Fatherboard said:
Well... this particular gps chip is quite useless, then. if my navigation program has to recalculate the route each time I stop at traffic light, then it seems that I either have to purchase a usb-based gps to pair with the HD2, or replace this device. I counted on it to perform well.
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Complain to HTC, perhaps if they get enough complains they will come out with a hotfix or a rom upgrade that fixes it. Nobody said that the hardware is not that good (though it's possible), but it could also very well be a bad implementation by HTC!!
Already did.
They have obviously denied my complaints.
thanks again, anyway.
I noticed this behaviour yesterday night, at about 10pm. I was playing with NoniGPSplot, and while I was completely still (and freezing me arse outside believe me), it was tracking a movement back and fro and all around in small step, keeping track of me traveling some meters still while I was standing in the same point.
It was night and I was in my big yard, so no sunrays nor moving vehicles around nor buildings over my head.
I think this behaviour is very well hidden in tomtom since it automatically puts you on a road, and "smoothens" the gps data by making you follow that road no matter what, but a "realtime" software like nonigps tracks that all so well. Gonna notify htc about it now.
Guys, let's not go overboard on this. Non-military GPS is only claimed accurate to around 20 metres, regardless of the quality of the receiver. It's the US Defense Department messing with your HD2, not HTC.
Stephen Selby said:
Guys, let's not go overboard on this. Non-military GPS is only claimed accurate to around 20 metres, regardless of the quality of the receiver. It's the US Defense Department messing with your HD2, not HTC.
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Yes, absolutely, I've noticed the same behaviour with all three of the BlueTooth GPS I used in the past. So, I would not be too quick to blame HTC for this.
my touch cruise's gps receiver worked with static navigation enabled to avoid this false movement. maybe this is just a usual behaviour?
Agree to that.
But regardless of the fact that the thing is not a military GPS system, It should do it's work correctly as for me the GPS is almost useless when driving slow or within a city. My 2nd phone (HTC DIAMOND) and 3 personal navigation devices are mounted in my car to compare and all work fine when the HD2 isn’t .
The GPS looses all the time the fix to the satellites and then quickly gets the fix back. when using a GPS monitor you can see that the satellites constantly moving really rapidly. (moving --> getting fix and loosing it again)
This is for 4 other reference devices which are running simultaneously not the case so it seems really an issue with the GPS device.
I tested this with different ROMs (1.44 Vodafone, 0.6 dutty WM 6.5.5, 1.66 stock and another one I cannot recall the producer anymore.)
Okay so now that I have my vibrant I tested it out (only a few times) but I did test it in different applications, websites, and maps and navigation. Yes in the gps and compass apps it doesn't pick up at all compared to my slide BUT in every other application, on google where it finds your location, on yelp, movie phone, maps, and navigation it finds my location each and every time. It doesn't get me lost, it doesn't show me going in a different direction, and it doesn't show me somewhere else.
What if the configurations or settings are different with samsung, what if the third party app is not completely accurate? Why else would every other program find my location if the app says I am not found by even 1 satellite? I think the"fix" is just a change of setting that helps the app not the gps or the phone.
Time will tell but for me it us working fine for now.
Sent from my SGH-T959 using XDA App
Well you can do gps tests within the os that say basically the same thing...
Ive used my gps with google navigate nermous times with no problem. in fact, it guided me on a 160mile trip just fine... What problems are people having with their gps?
Well, I've only had the phone for a day, so I'm still getting used to the quirks coming from a G1. GPS so far is the biggest disappointment. Android has been pushing location based stuff since the beginning, so the lack of a solid GPS is really screwing up some of my favorite apps. Locale for instance, it's worthless. It can't ever find me. The G1 always worked fine with it on Donut, Eclair, and Froyo.
Google Maps is the ONLY app I have that seems to even be able to get a rough idea where I am, and even then its circle is pretty big, about 4 city blocks. That's not GPS, that's network location, and it's fine for what it is, but not good enough when there aren't a lot of cell towers around. At home, it puts me out in the middle of a corn field. All the time I'm in maps, the GPS icon is up there blinking at me, telling me it can't lock. I've seen it work a couple times, for a short while. In GMaps and in GPS Test. But it takes a LONG time. The G1 could get a lock indoors in about 10 seconds. The Vibrant takes minutes, even with the A-GPS turned on in the test menus. That's insane. And it's not any better outside with a clear sky view. That might be acceptable, if it could hold the lock, but it doesn't.
Even stranger, in GPS Test, I get a single colored bar saying it's using that signal. There are 6 more with the same or higher signal strength being ignored. Very odd. Something is wrong with this GPS. It could very well be software, but Samsung needs to get on this and fast. If I can't find a way to get acceptable GPS performance within my 14 day period, I will likely return it. That will really suck, as otherwise I really like the device, but I need a decent GPS.
ttabbal said:
Even stranger, in GPS Test, I get a single colored bar saying it's using that signal. There are 6 more with the same or higher signal strength being ignored. Very odd. Something is wrong with this GPS.
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This has been my experience as well, and I found the same thing when trying a friend's phone. If only T-Mobile/Samsung would acknowledge that there is a problem and say they are working on it...
No problem here
But as I came from the G1 I use Google Maps exclusively. I haven't had a single problem with it. Inside my house I can get a fix on my location on the map, exactly where it should be. Are you guys using the TeleNav?
ttabbal said:
Even stranger, in GPS Test, I get a single colored bar saying it's using that signal. There are 6 more with the same or higher signal strength being ignored. Very odd. Something is wrong with this GPS. It could very well be software, but Samsung needs to get on this and fast.
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I have the same issue... I can only ever lock on to 1 sat. This is not right. My G1 would lock on to many birds.
zoid_99 said:
I have the same issue... I can only ever lock on to 1 sat. This is not right. My G1 would lock on to many birds.
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I wonder if GPS Test is either wrong about that, or more likely, getting bad data from the OS or GPS driver. IIRC they are just parsing the NMEA data from the GPS driver, so "garbage in, garbage out". You don't get 20ft accuracy with 1 satellite being used.
I fooled with the settings in the "GPS fix 101" thread and got the thing working decently. Took a number of tries, and we'll see if it keeps working over time.
This really is something that TMO and Samsung should acknowledge and at least promise a fix for. Preferably with a close release date. And we shouldn't have to wait for Froyo either, get us a fix for JUST the GPS and a lot of people would be VERY happy. Well, that and the compass, that thing is even more worthless than the GPS before the fixes.
For the poster with Google Maps working, did you try with network locations disabled? Is the GPS icon in the status bar flashing or solid? If it's flashing, you DON'T have a GPS lock. Maps seems to be really good at using the network location stuff. I also enabled Skyhook in the GPS settings screen and Maps really seems to like that. Doesn't help with GPS performance though.
This thread is idiotic.
cashless said:
This thread is idiotic.
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Wow.. that statement was idiotic. Maybe you aren't having the GPS issues that others are having but this thread is helping me debug and decide weather or not I'm keeping the Vibrant or returning it.
You guys are not alone. There is obviously something wrong with either the hardware, or the software. Either way, the buyer's remorse period is halfway through, and neither company has said so much as a peep.
I will definitely be returning my device by the time the remorse period expires. What a shame that would be, because I really love this screen. All it would take is for T-Mobile and Samsung to acknowledge the problem, and state that a fix is on the way.
Here's my post, detailing my contact and findings with the two companies.
It's been a few days now, and I've heard nothing back. Never a good sign.
EDIT. Got it working
Care to share?
Well like everyone I had the GPS issue and it was frustrating. I do run an app killer and I always notice many apps (especially the preloaded ones) Keep launching themselves. It got rather irritating. Specifically Telenav.
I noticed with Telenav my GPS would be very flaky. Once I got "killed" it the gps seemed to improve. I thought to myself maybe I'm just being paranoid.
Did a bit of research and found an app called "Start UP Auditor" which completely kills an app and restricts it from every starting up again. My gps seems to be working much better now.
I drove a few miles and on the Verrazano Bridge here in NY and the GPS was super percise. When I was at the end of the block it was at the end of the block as well at the same time. Not like it was before.
Now I can launch google maps and it will find me exactly in front of my house and not 200 feet away.
Takes a solid minute to lock on. Not more but not less unfortunately. So there still is a bit of a problem but for me at least it has exponentially gotten better. Versus it not even locking on previously.
I think I might be on to something. I cannot give all credit to me because I saw on a Tmobile forum someone say that they think the problem might be with the self launching apps so that's where I started to draw conclusions.
EDIT: Scratch that one min thing. It seriously just now took me 10 seconds to lock on and the GPS to start talking to tell me where to turn inside my house. Issue fixed?
I completly removed TeleNav and I still have GPS issues... It is not any software causing this problem. It is a Hardware / Firmware / Driver issue.
Sent from my SGH-T959 using XDA App
gravis86 said:
I completly removed TeleNav and I still have GPS issues... It is not any software causing this problem. It is a Hardware / Firmware / Driver issue.
Sent from my SGH-T959 using XDA App
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Same here, one of the first things I did after rooting was remove all the bloatware, and Telenav was one of them.
gravis86 said:
I completly removed TeleNav and I still have GPS issues... It is not any software causing this problem. It is a Hardware / Firmware / Driver issue.
Sent from my SGH-T959 using XDA App
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Hmmm... Interesting.
My GPS issues seem to have disappeared after killing Telenav.
This just takes me back to the drawing board once more. I just do not understand...
I would like to see others responses. Does there happen to be vibrants with different firmwares?
So what happened to me?
Was it some magical stroke of luck?
Wow.
Initially, disabling TeleNav gave me a significant improvement in GPS performance. Indoors, I went from having 50-60ft. of accuracy (with multiple locks), to 12-15ft. of accuracy with a single lock. Initial accuracy was in the upper 40s, but quickly dropped to the highest accuracy I've seen with the device (the 12-15ft. figure) - indoor or outdoor - within a minute. Crazy.
Outdoor, on a perfectly clear sky, the best I've achieved was previously 25ft. of accuracy.
I rebooted (the phone froze, wheee!), with TeleNav still selected as disabled, and now, I'm only getting 30-52ft. of accuracy with a single lock. This took about two minutes to come down from 170ft. or so.
GPS settings have been switched to 'Automatic', from the stock supl server, for all of these tests.
Maps still shows me in Issaquah, initially (incorrect data), but quickly updates my position my exact location (within a few seconds). Previously, Maps would take at least a half hour to place me in even the correct city! Margin of Error: ~50ft. or so (shows me on the street, rather than on my property), within seconds.
Compass, as expected: still totally ****ing broken and ****ty.
I can confirm that - besides not being able to lock onto more than a single sat - I'm seeing drastic improvements. Thanks for pointing this out.
Still, I'm not sure the improvement will be enough to convince me to hang onto the device while we wait to hear from Samsung. :/
Jon C said:
Wow.
Initially, disabling TeleNav gave me a significant improvement in GPS performance. Indoors, I went from having 50-60ft. of accuracy (with multiple locks), to 12-15ft. of accuracy with a single lock. Initial accuracy was in the upper 40s, but quickly dropped to the highest accuracy I've seen with the device (the 12-15ft. figure) - indoor or outdoor - within a minute. Crazy.
Outdoor, on a perfectly clear sky, the best I've achieved was previously 25ft. of accuracy.
I rebooted (the phone froze, wheee!), with TeleNav still selected as disabled, and now, I'm only getting 30-52ft. of accuracy with a single lock. This took about two minutes to come down from 170ft. or so.
GPS settings have been switched to 'Automatic', from the stock supl server, for all of these tests.
Maps still shows me in Issaquah, initially (incorrect data), but quickly updates my position my exact location (within a few seconds). Previously, Maps would take at least a half hour to place me in even the correct city! Margin of Error: ~50ft. or so (shows me on the street, rather than on my property), within seconds.
Compass, as expected: still totally ****ing broken and ****ty.
I can confirm that - besides not being able to lock onto more than a single sat - I'm seeing drastic improvements. Thanks for pointing this out.
Still, I'm not sure the improvement will be enough to convince me to hang onto the device while we wait to hear from Samsung. :/
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Yea like I said in the OP the fix is better but there definitely is a problem that needs to be addressed. That might be either hardware or firmware, All thats left is to wait for sammy to fix it up. However my GPS performance for my needs is more than exceptional.
I have noticed that while running GPStest, Google Maps starts to work. Something is wrong with the API.
If anyone is getting black screen freeze ups, disabling GPS will clear that right up.
And, we're back to square one. So much for that.
Location services can no longer locate me, and show that I'm in a neighboring city. Nothing I adjust fixes this for more than a short period of time.
Oh, Samsung...
dattaway said:
I have noticed that while running GPStest, Google Maps starts to work. Something is wrong with the API.
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It seems to me that it is definitely a software problem. I don't think the hardware is bad. (The gps chip?)
heygrl said:
If anyone is getting black screen freeze ups, disabling GPS will clear that right up.
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I drove for miles and had nothing. Though if I am not using GPS I always turn it off to conserve battery.
Jon C said:
And, we're back to square one. So much for that.
Location services can no longer locate me, and show that I'm in a neighboring city. Nothing I adjust fixes this for more than a short period of time.
Oh, Samsung...
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Click to collapse
I wonder if they can't even find the issue yet. It will probably be fix in the 2.2 update.
I removed TelNav within 4days of owning my phone and it really for me hasn't changed a thing.
What helped me was turning off the wireless location feature. From what I noticed it looks for your location based off the cell towers first then it looks for your location via GPS. If its slow to find you via wireless then well its slow to find you via GPS too.
I didn't really tried the GPS when I saw the threads saying there was a problem with it and I read somewhere about "how to fix it" so I applied the fix before even using the GPS before, so I have no clue if I had problems or not, but after the fix, the GPS locks in about 10 to 15 seconds and gest my location on the spot, even indoors.
just change the GPS settings to google servers
Directly after rebooting my gps/navigation seems to work much better.
To make it more clear... I'll be using my phone throughout the day and then i'll try to use navigation. Usually it will just keep trying to find the route but it never actually finds it. I'll reboot the phone and it'll find my location and the route in <10 seconds.
kizer said:
I removed TelNav within 4days of owning my phone and it really for me hasn't changed a thing.
What helped me was turning off the wireless location feature. From what I noticed it looks for your location based off the cell towers first then it looks for your location via GPS. If its slow to find you via wireless then well its slow to find you via GPS too.
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I believe the wifi and GPS share the same antenna. Anyone know which antennas do what for sure?
Our cellular antenna is at the bottom under the bump. The one at the top next to the antenna port does the rest.
heygrl said:
If anyone is getting black screen freeze ups, disabling GPS will clear that right up.
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Thanks for this tip, I hadn't caught this in the other GPS threads.
I ran and used My Tracks but forgot to turn on GPS. When I tried nav it could not get a fix until I restarted. Next time I'll try killing conflicting apps.
Sent from my SGH-T959 using XDA App
I just deleted the Tel-Nav app and now my GPS locks on in about 10 seconds and is dead on accurate. I even drove 165 miles today and never dropped a GPS signal. I could never do that before.
Does anyone know why the times are off one the gps sensors? My local time is 10:51, but gps test has it as 18:51 that is about 8 hours off.
Sent from my SGH-T959 using XDA App
We all know that the GPS unit on our beloved SGS sucks badly. Firstly it takes ages and ages to find a good signal, and secondly it chews up bucketloads of battery to get there.
The other day I was talking to someone about GPS units within some handheld devices at work, and he told me something that completely blew me away - how GPS units ACTUALLY work as opposed to how most people think they work.
Firstly let me preface this by saying that he used (and I will use) the "Lies to Children" method of technical communication. If you are not a Terry Pratchett fan, it basically means that instead of explaining a subject to the Nth degree and getting the full detail across, you sum it up with what is essentially and technically a lie - but one that's a half-truth that will pave the way for future understanding.
Example? "The sun rises in the east and sets in the west". Comparatively speaking against the Earth, the Sun does NOT move. The actual truth is the sun moves within the galaxy and within the galaxy cluster and within the universe. The earth also moves in a similar manner and also rotates on its axis with a slight wobble that technically provide seasons. How does that relate to a 5 year old? "Yeah, uh, kid. The sun, you see, it rises in the east". A "lie" but one that works for everyone, and when their brain absorbs enough other information you can explain it properly (with another "lie", but one that's more truthful than the previous one)
Back to the topic:
I thought, like most of you probably think, that a phone's GPS works by having some kind of 2-way method of communication. When you enable the GPS unit and go into maps, the device starts broadcasting to the satellites to say "I'm here, now where is 'here'?" That's not the case.
It works a bit like this (and pardon the analogies)
Let's say there are 3 satellites are in geosynchronous orbit at fixed locations. For the sake of the description we'll call them FRED, GEORGE, and BILL. A lot of time and money was spent to make sure that they don't vary that location by a factor of a few cm before they re-correct their location. A bunch more time and money went into their internal time-keeping mechanisms so that they are also VERY accurate.
From their location they broadcast a signal outward. Fred says "HI I'M FRED LOCATED AT POSITION X AND THE TIME IS SUNDAY 18TH MARCH 2012 7:15PM AND 38.123456789 SECONDS"..."HI I'M FRED LOCATED AT POSITION X AND THE TIME IS SUNDAY 18TH MARCH 2012 7:15PM AND 38.123456790 SECONDS" and so on.
George says "HI I'M GEORGE LOCATED AT POSITION Y AND THE TIME IS SUNDAY 18TH MARCH 2012 7:15PM AND 38.123456789 SECONDS"..."HI I'M GEORGE LOCATED AT POSITION Y AND THE TIME IS SUNDAY 18TH MARCH 2012 7:15PM AND 38.123456790 SECONDS" and so on.
And Bill...I can't be stuffed writing it, let's just say Bill screams out his location and the current time, multiple times a second.
Now, while some satellites broadcast in higher or lower timings, the basics are the same: Current position, plus the current (accurate) time. (Some also send information regarding the other satellites it "knows" around it. Eg, "HI I'M BILL AT POSITION Z AND THE TIME IS BLAH AND I CAN SEE GEORGE AND FRED. THEY DON'T SAY MUCH, SO IT SURE IS LONELY UP HERE").
My point here is that the satellite neither knows nor cares who you are or where you are, it just pumps out that racket like a noisy teenager with a new stereo and what they THINK is the coolest music ever.
When the 3 signals are received on the ground by the GPS unit, it works out: "Bill thinks it's THIS TIME....George thinks it's THAT TIME...and Fred thinks it's this OTHER TIME....that means my distance from each one is actually THIS FAR and the real time is NOW". From that you can bang your location in LATITUDE and LONGITUDE on a map.
Sure, there are complications due to altitude and speed and direction, and you really need more than 3 satellites to work out where you are. But the reality is that, based on the lag in the signal from transmission to receiving (able to be calculated due to the speed of light), we can work out how long each signal took to get to the unit and therefore how far from the satellites we are. If you know where the satellite is supposed to be, you can work out where you are on the globe.
It really is that simple.
So when I found all of that out, I asked the question: If the satellite is really all that counts in this case, why does our GPS blow? In fact, why does any GPS work better than others?
Well, there are multiple factors:
Firstly, just like a good barman or psychologist, some "listen" better than others. The PASSIVE radio signal needs to be received by a unit that has a decent antenna and doesn't have other electrical crap affecting it. Anyone look inside their phone and see the antenna (and it's location)? Yup, it's in a pretty bad position and it's a pretty bad antenna.
Even if we were somehow to isolate the GPS unit and bring it out away from the interference, it's a pretty bad receiver. If you've ever listened to a transistor radio and compared it to a $4000 stereo unit, you know what I mean. Noise = bad data = bad location finding.
Secondly, the signal needs to be interpreted. When each broadcast hits the phone, the receiver accepts it and shunts it to the processor to work out. Slower phones can process less signals, especially when the OS may put a limit on how much processor time should be dedicated into working out the signals (there's no point using 100% of your processor when that means you can't display it properly on the map or let the user actually interact with the maps app)
Thirdly, we don't know all the positions of the satellites. When the signals first start getting processed, your phone communicates with the NTP servers it has located in your GPS.CONF. It asks which satellites are where and where that actually may be on the globe. Remember how I said each satellite tells you it's position? That was a "lie to children" moment. The damned thing is in the SKY after all. So, while we technically know where it is, the information means jack and sh*t to the GPS unit unless it has more information available.
What I mean here is: What part of the world can that satellite see/broadcast to? The satellite doesn't know or care, and it's not broadcasting that information at any case. There's more than a couple of satellites up there, so the phone needs to check back the NTP.ORG to work out some basics. As your phone uses the GPS function more and more, it stores up the addresses of the satellites that you know and love in your neck of the woods (including ones that are not geostationary) and will need to rely less on a data connection.
That's why when you use GPS the first time after a fresh flash it is just plain crap, but after a few more tries it works better. And that's why it's important to use FasterFix or a like app to nominate the closest/best NTP server for you - the closer servers respond quicker over the 'net and also have the list of "closest" stationary satellites stored at the front of the file. If you're in Australia you don't care about the 'merican or European sats, but they come afterward "in case you're overseas"
Lastly, when you take it all into account, if you have bad weather or tall buildings around you, then the signals blasted down from on high either get muted, muddled, or bounced around. The error correction in our phones is non-existent - it doesn't actually need to be due to the fact it's a PHONE and not a GPS unit, but some devices can and do filter out the known "dodgy" signals before processing. I'm pretty sure that when the techies run out of toys to add to or fix in our phones, they'll add altimeters and thermometers and they'll fix the GPS post-processing to get the signal down pat.
In case you're wondering, the whiz-bang GPS units that can get extra awesome resolution (down to beyond cm) have the list of every single satellite location up there stored internally, the on-board processor is dedicated to working out what the signals mean, and the GPS chip itself normally has a great big honking antenna on it and is extra receptive. Ours is a 2 dollar job from some bulk offload sale.
There you have it. Thanks for letting me brain dump. Hope this helps some people's understanding!
Interesting. I had always thought it was a simple two-way communication between the phone and a geostationary satellite. But in retrospect, that would be extremely inaccurate seeing as how the attenuation over such a long distance, as well as the interference with other phones (which might be using the same frequency because GPS is not network controlled, unlike calls) would make it difficult for the satellite to tell where the signal came from. This explanation makes much more sense. Thanks!
So, its still better to use an app like GPS Aids so the GPS would be "up" faster... Thanks for explanation, you sir, get a thanks.
Wow! Nice post, well written and very informative!
But I don't understand, how the help is GPS free when all this technology is so expensive!?
Sent from my GT-I9000 using XDA
Yes. Good post. Except the GPS satellites aren't geostationary. They orbit the earth twice a day at an altitude of approximately 20.000km. There are 6 different orbit planes and 4 satellites per orbit.
A geostationary satellite sits directly above the equator at an altitude of about 36.000km. One orbit lasts excactly one day and thus the satellite appears as if it's standing still in the sky.
You can google all that if you like.
GPS would be simple if all the satellites were geostationary, but that would make triangulation very difficult. Especially around the polar areas. Therefore they must be orbiting crisscross all over the globe. But that also makes geostationary orbits impossible (it is only possible directly above the equator).
Thanks given simply for the Terry Pratchett reference (I'm addicted to Discworld novels)
Here are my 2 cents about this whole "closer NTP server = better results"
1) NTP server is just a time server. It doesn't store any info regarding any satellite in your neighborhood. That's the role of A-GPS server - in our case it's supl.google.com that you see in every gps.conf.
2) We all get our current time from our mobile provider or manually setting it in settings. So we don't sync our clock to NTP server time. Our phone will just use NTP to figure out the offset - i.e. how accurate our clock really is. It can also take into account the delay factor caused by network latency since it's something relatively easy to measure. So in the end of the day it won't really matter what NTP server you use as long as it works and you don't have any network issues with it.
From my experience all these NTP games are one big placebo effect.
The only tips I got for better GPS are:
A) Clear GPS cache after not using it for a long period of time (or let android do that for you eventually).
B) Use mobile network data for faster fix (A-GPS).
C) Keep the antena free from any obstacles - In car place the phone directly under the front glass, don't expect it to work under the roof.
While running if you use armband, place the phone with its screen toward your arm since if placed otherwise your arm will blocks the gps signal completely.
Any one know why mine is fine and grabs lock within 10 seconds indoor with iGO and GPS test?
I didn't f*)Kin camp outside a electronic store JUST to get one on release date I got one from later batch which fixes hardware GPS reception issue
All GPS use one-way communication.. it would become too expensive n complicated to have two-way communication
1) The GPS receivers here on earth would require complicated and high power circuitry to send signals to satellites miles above the earth. It would suck a battery dry in minutes
2) The GPS satellites would require to handle communication with an exponentially increasing number of GPS units on the ground. That would require huge processing power, multiple channel support and communication management to avoid clashes between communicating units. Satellites are situated so high up that signals to and from satellites accrue a lot of noise n distortion.. For proper signals, satellites can only transmit data at very low data rates and have low bandwidth..
GPS requires exact timing, and I mean atomic clock exact. Its impossible to have atomic clocks in today's small devices. So satellites have a very accurate atomic clock on board.. Heck, some satellites have 3 on board to correct clock drift and error!! Even then, GPS devices were very expensive.
Then, some scientist found a way to find the exact location and time by using the really small timing variations in satellite signals. Coz of that, we can now afford GPS chips at $50..
Our phones don't have space for large ceramic antennas (one GPS unit I have has a 25x25x4 mm antenna on top!!) And the timing variation trick helps even low power units pick up satellite signals, but they are slightly less sensitive.. They won't be able to pick up weak signals, which your car nav unit will..
Also, processing GPS data doesn't take that much processing.. Almost all GPS units output their data in a standard format called NMEA format and the location data looks something like:
$GPGGA,<time>,<latitude>,<longitude>,<fix quality>,<no. of satellites>,<altitude>......
All the processor has to do is use this data.. A processor doesn't have to calculate anything at all with regards to actually locating the device. The GPS chip does it all..
Sorry for the really long post.. I hope it makes sense.. I'm doing a project which uses a GPS unit, so I've been studying on it..
First let me start by saying that I have a habit of drunk posting. So I logged into XDA today at work and went "huh? An extra bunch of 'Thanks'? What the hell have I done now?"
Which means that while the information in the OP does a decent job of summing up what I was told, some was a little off. Cheers for pointing out where I got things wrong.
Remember, last week "my mind = blown" by the fact that GPS isn't 2-way...which makes sense but is one of those things that I never considered...
Don MC said:
Yes. Good post. Except the GPS satellites aren't geostationary. They orbit the earth twice a day at an altitude of approximately 20.000km. There are 6 different orbit planes and 4 satellites per orbit.
Click to expand...
Click to collapse
You are quite right, there are a whole bunch of sats whizzing around up there in set orbits. Some of them "talk" to ground stations to get updates about the world in general, but a bunch just go screaming past blaring out their message.
I asked my mate at work who told me about how GPS works....his response? "Yeah, Lies to Children works like that." Apparently a combination of his half-explanation and my beer meant I got something wrong there. Sorry.
To give the full information about the different sats flying about, and how they get send the information....well, apparently it was easier to say "geostationary" !!
mike.sw said:
Here are my 2 cents about this whole "closer NTP server = better results"
1) NTP server is just a time server. It doesn't store any info regarding any satellite in your neighborhood. That's the role of A-GPS server - in our case it's supl.google.com that you see in every gps.conf.
2) We all get our current time from our mobile provider or manually setting it in settings. So we don't sync our clock to NTP server time. Our phone will just use NTP to figure out the offset - i.e. how accurate our clock really is. It can also take into account the delay factor caused by network latency since it's something relatively easy to measure. So in the end of the day it won't really matter what NTP server you use as long as it works and you don't have any network issues with it.
From my experience all these NTP games are one big placebo effect.
Click to expand...
Click to collapse
Again, you're right. But in the GPS.conf file there are both NTP and A-GPS servers. I was of the understanding the NTP address information also gave ...wait, disregard - just Googled that.
NTP only gives you time. And it won't matter which NTP server you get unless you have networking issues. I suppose the answer there lies in the fact that a "closer" NTP server will get you a quicker response to begin with, so your phone can start the process of working out the offset quicker....
Good tips, though I'm too much of a beer drinker to go running. Screen in or out.
ilabs said:
All GPS use one-way communication.. it would become too expensive n complicated to have two-way communication
1) The GPS receivers here on earth would require complicated and high power circuitry to send signals to satellites miles above the earth. It would suck a battery dry in minutes
2) The GPS satellites would require to handle communication with an exponentially increasing number of GPS units on the ground. That would require huge processing power, multiple channel support and communication management to avoid clashes between communicating units. Satellites are situated so high up that signals to and from satellites accrue a lot of noise n distortion.. For proper signals, satellites can only transmit data at very low data rates and have low bandwidth..
Click to expand...
Click to collapse
Correct...but kids these days also assume that steak literally grows on trees. Assumptions are the mother of all....
ilabs said:
Our phones don't have space for large ceramic antennas (one GPS unit I have has a 25x25x4 mm antenna on top!!) And the timing variation trick helps even low power units pick up satellite signals, but they are slightly less sensitive.. They won't be able to pick up weak signals, which your car nav unit will..
Click to expand...
Click to collapse
Correct, that was my point about the crappy GPS chip being like a crappy transistor radio. The combination of the quality of the chip plus the really really bad antenna (and it's position) means that people will not get car-gps like quality from their phone....and they shouldn't !!!
ilabs said:
Also, processing GPS data doesn't take that much processing.. Almost all GPS units output their data in a standard format called NMEA format and the location data looks something like:
$GPGGA,<time>,<latitude>,<longitude>,<fix quality>,<no. of satellites>,<altitude>......
All the processor has to do is use this data.. A processor doesn't have to calculate anything at all with regards to actually locating the device. The GPS chip does it all..
Click to expand...
Click to collapse
You're talking about the "final" output, but when I mentioned processing I meant the processing of the signal received.
I asked again about this. It was explained thusly: If you have interference in the form of tall buildings (for example) then the signal will actually bounce around a bit before being picked up. That "echo" can sometimes give a false reading if you took that one bit of information as a whole, as it's not a true representation of the time it took for the signal to get down from the sat.
So the device collects constantly and shunts that information to the processor to determine the length of time between when the sat spat it out and when the unit received it.
Now say every 10th "message" is a bounced/echo one. If the device is only able to process every 5th message, then it's potentially going to have up to half the messages be a dodgy echo job = bad location. It will catch up, eventually, but will take longer to know something weird is going on.
If, on the other hand, the more powerful processor was able to work out every 3rd message or more, then a more accurate fix comes quicker.
ilabs said:
Sorry for the really long post.. I hope it makes sense.. I'm doing a project which uses a GPS unit, so I've been studying on it..
Click to expand...
Click to collapse
Dude, the more people who post (sober) the better the information we have!!! Post away and make it long! Mine was!!
MrAndroid12 said:
Any one know why mine is fine and grabs lock within 10 seconds indoor with iGO and GPS test?
I didn't f*)Kin camp outside a electronic store JUST to get one on release date I got one from later batch which fixes hardware GPS reception issue
Click to expand...
Click to collapse
Luck....pure kiwi luck? lol.
I know my hardware blows. Takes anything from 30 seconds to 1 minute to get a dodgy half-lock.
I was thinking about packing it in for a new phone but a) still got a plan to pay off and b) ICS made the device more than useable in every other aspect.
wogfella said:
You're talking about the "final" output, but when I mentioned processing I meant the processing of the signal received.
I asked again about this. It was explained thusly: If you have interference in the form of tall buildings (for example) then the signal will actually bounce around a bit before being picked up. That "echo" can sometimes give a false reading if you took that one bit of information as a whole, as it's not a true representation of the time it took for the signal to get down from the sat.
So the device collects constantly and shunts that information to the processor to determine the length of time between when the sat spat it out and when the unit received it.
Now say every 10th "message" is a bounced/echo one. If the device is only able to process every 5th message, then it's potentially going to have up to half the messages be a dodgy echo job = bad location. It will catch up, eventually, but will take longer to know something weird is going on.
If, on the other hand, the more powerful processor was able to work out every 3rd message or more, then a more accurate fix comes quicker.
Dude, the more people who post (sober) the better the information we have!!! Post away and make it long! Mine was!!
Click to expand...
Click to collapse
Haha.. Yeah, the assumptions that you hear from time to time!! Makes even standard fiction seem possible!!
When I was talking about the processing, yeah, it was the final processing. But the processing of the GPS signal is only done by the GPS chip, not the processor to which the data is output. Generally GPS satellite signal frequencies are such that they die out very quickly when reflected off or passing through objects and buildings. That's why you get the best signal out under the open sky. The processing of the final received signals is done completely by the GPS chip. A standard GPS chip has only TX/RX serial pins apart from power pins. As soon as you power it up, it starts spitting out GPS data. Externally interfaced processors don't have to calculate anything at all.
Apart from this, everything is spot on!!
---------- Post added at 04:34 PM ---------- Previous post was at 04:27 PM ----------
MrAndroid12 said:
Any one know why mine is fine and grabs lock within 10 seconds indoor with iGO and GPS test?
I didn't f*)Kin camp outside a electronic store JUST to get one on release date I got one from later batch which fixes hardware GPS reception issue
Click to expand...
Click to collapse
Generally, when you first start up a GPS unit, its called a cold start coz it takes time. It will take time to scan for satellites and make a database of satellites around. Once it has at least 3 satellites in view, it has enough data to perform a proper triangulation to give your location. As the antennas on a phone are weaker, there's a certain error in a signal, which is why Google maps first shows your estimated location in a blue circle. As you begin to move, more data like heading and stuff is known and your position becomes accurate.
Sometimes even I get a lock in 10 seconds, sometimes not even in half an hour. That happens when there are no strong satellites above. If you always get a lock, I guess you're lucky to have a good number of satellites hovering over your phone like guiding angels..
wogfella said:
NTP only gives you time. And it won't matter which NTP server you get unless you have networking issues. I suppose the answer there lies in the fact that a "closer" NTP server will get you a quicker response to begin with, so your phone can start the process of working out the offset quicker....
Click to expand...
Click to collapse
The "quicker" result may be important if you query ntp servers every second (the default rate for GPS sample I think), however ntp is being queried once in a while - not sure the exact interval maybe one of the developers here can help with that.
If everyone of us would query the ntp servers every second they would be hammered to horrible death.
In "normal" NTP setups, client systems, like your desktop, query a small number (perhaps between 1--10) NTP servers every so often, e.g. once per minute (or 64 seconds in a common UNIX implementation). This can vary depending on response.
NTP is designed to get microsecond wall-clock time accuracy despite round-trips to NTP servers often taking tens, or even hundreds of milliseconds.
I believe most Android phone GPS chips update position once per second. There are apps that will confirm this.
I don't believe there's any need to repeatedly query NTP servers every second.
However, the hardware clocks in phones are terrible. Mine drifts up to one second per day, until the clocksync app uses an NTP query to drag it back to reality. Note this is different to how it's normally done on a PC: there, the OS clock is sped up or slowed, so that the time can gradually skew towards reality. For a large difference, the time has to be stepped, all in one go, which isn't ideal from an OS perspective (e.g. timed callbacks, etc).
So I can see that more frequent NTP checks might help a little, for GPS, but not a lot.
Note that consumer GPS units (e.g. automotive, handheld) do not use NTP at all, nor do they have expensive hardware clocks. So I'm not at all convinced why NTP is "required" on Android GPS, unless it's because most phones default to getting the time from the mobile network, which can be *minutes* off.
Finally, sadly, none of the above even remotely explains why our SGS phones have a reputation for (or in fact "are") worse at GPS than other similar phones...
Edit: meant to add: the latter is perhaps mostly likely explained by a combination of poor antenna design, and sub-optimal GPS implementation in the Broadcom chip (which I believe is the one involved).
I wanna kno why the x10 has such a bad camera
OMG. Counter Strike On Android! http://cs-portable.net/
I wanna kno why the sgs has such a bad camera
Very interesting
ilabs said:
Haha.. Yeah, the assumptions that you hear from time to time!! Makes even standard fiction seem possible!!
When I was talking about the processing, yeah, it was the final processing. But the processing of the GPS signal is only done by the GPS chip, not the processor to which the data is output. Generally GPS satellite signal frequencies are such that they die out very quickly when reflected off or passing through objects and buildings. That's why you get the best signal out under the open sky. The processing of the final received signals is done completely by the GPS chip. A standard GPS chip has only TX/RX serial pins apart from power pins. As soon as you power it up, it starts spitting out GPS data. Externally interfaced processors don't have to calculate anything at all.
Apart from this, everything is spot on!!
---------- Post added at 04:34 PM ---------- Previous post was at 04:27 PM ----------
Generally, when you first start up a GPS unit, its called a cold start coz it takes time. It will take time to scan for satellites and make a database of satellites around. Once it has at least 3 satellites in view, it has enough data to perform a proper triangulation to give your location. As the antennas on a phone are weaker, there's a certain error in a signal, which is why Google maps first shows your estimated location in a blue circle. As you begin to move, more data like heading and stuff is known and your position becomes accurate.
Sometimes even I get a lock in 10 seconds, sometimes not even in half an hour. That happens when there are no strong satellites above. If you always get a lock, I guess you're lucky to have a good number of satellites hovering over your phone like guiding angels..
Click to expand...
Click to collapse
My cold starts take no longer than 10 seconds for a 50-30 meter lock. After it is warmed up, GPS takes a matter of 2 seconds to grab lock @ 10 meters and 5 shortly after.
---------- Post added at 07:41 PM ---------- Previous post was at 07:40 PM ----------
MattyOnXperiaX10 said:
I wanna kno why the sgs has such a bad camera
Click to expand...
Click to collapse
It's not that bad, is it?
I wanted to shoot a video for my YouTube channel using my mums phone. Galaxy s and it wasn't focusing on the camera, video quality was bad (sorry for of topic)
Ask us any Android Related Question @FeraLabsDevs on Twitter or @HowToMen
MrAndroid12 said:
My cold starts take no longer than 10 seconds for a 50-30 meter lock. After it is warmed up, GPS takes a matter of 2 seconds to grab lock @ 10 meters and 5 shortly after.
---------- Post added at 07:41 PM ---------- Previous post was at 07:40 PM ----------
It's not that bad, is it?
Click to expand...
Click to collapse
I get the same start timings, provided there are satellites to lock onto.. Sometimes my cold start time is a little over a minute!! But with no satellite cover, I could be better guided by a rock than my phone..
Sent from my GT-I9000 using XDA
Curious if someone else has this issue:
My location using GPS, High Accuracy or Device Sensors is consistently off by several miles several times a week. Coincidentally, it likes to stick me to the same location that's along my commute to work. It does not update or change from this location.
If I select Battery Saving, it updates and is correct. I assume since this doesn't use the GPS receiver, which may be the source of my pain.
If I go back to the other modes, it goes back to the erroneous location. Recalibrating doesn't seem to help as this may fix the compass, but my location is still wrong. This happens every couple days, not all the time, but it is the same location it likes to stick me to, as if it's offset by my current location (since that location is work and that's the same daily then it makes sense the offset location is always the same.)
I don't know how to resolve that or discern a cause. And of course, if you don't use High Accuracy, most everything is designed to complain over and over again that you're in the wrong mode. You can imagine this make getting a Lyft or Uber a bit of a pain and interferes with Smart Locations. Anyone have a similar experience?
bitter1 said:
Curious if someone else has this issue:
My location using GPS, High Accuracy or Device Sensors is consistently off by several miles several times a week. Coincidentally, it likes to stick me to the same location that's along my commute to work. It does not update or change from this location.
If I select Battery Saving, it updates and is correct. I assume since this doesn't use the GPS receiver, which may be the source of my pain.
If I go back to the other modes, it goes back to the erroneous location. Recalibrating doesn't seem to help as this may fix the compass, but my location is still wrong. This happens every couple days, not all the time, but it is the same location it likes to stick me to, as if it's offset by my current location (since that location is work and that's the same daily then it makes sense the offset location is always the same.)
I don't know how to resolve that or discern a cause. And of course, if you don't use High Accuracy, most everything is designed to complain over and over again that you're in the wrong mode. You can imagine this make getting a Lyft or Uber a bit of a pain and interferes with Smart Locations. Anyone have a similar experience?
Click to expand...
Click to collapse
I'm having some issues I don't know if there is a fix I remember you use to be able to flash a file back when I had galaxy s5 to make the GPS more accurate
i have some problems with my gps too... it's totally unaccurate, can't track my position fast enough while i'm driving... but truth to be told, i haven't looked into it enough to say if it's fixable or not. last time i tried Here maps it was pretty much unusable...