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I bought the HTC Touch HD a few weeks ago and noticed that the accuracy is not just bad, but atrocious. It can't even locate me within a 300 meter radius. Is that normal? Does anyone else have this problem? I am using the latest Google Maps.
Thanks in advanced.
I would try a proper GPS program and see if it is the same, if so your HD is faulty.
No problem here. .Maybe silly question, but did you click on "Use GPS"?
--cheerios
skotler said:
I bought the HTC Touch HD a few weeks ago and noticed that the accuracy is not just bad, but atrocious. It can't even locate me within a 300 meter radius. Is that normal? Does anyone else have this problem? I am using the latest Google Maps.
Thanks in advanced.
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Are you sure you have a satalite lock? Google maps also determines position from cell towers and gives an estimate to your location within approx 500M. Once gps is activated and satlites have been aquired, a more accurate position is displayed (and i get a blue triange above the location - i guess to indicate actual position).
The little blue trianlge shows the direction you're moving - so the GPS is pretty accurate! Sometimes it doesn't get a lock for a while (it'll say at the top-right when it has active satellites) - if not, then it just uses that cell tower triangulation thing which gets it within about 500m as mentioned above.
aabye said:
No problem here. .Maybe silly question, but did you click on "Use GPS"?
--cheerios
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Click to collapse
Ya, it is on.
It can get working when I'm on the move, but as soon as I am still, it screws up. For instance, I can be driving to work and it works fine as far as telling me where I am at the moment. As soon as I close it and reopen it at work, it tells me I am somewhere 300-500 meters from work.
I guess I don't understand how it can work so well on the move, but as soon as I need an accurate reading, it is way off. Does this happen to anyone else?
skotler said:
Ya, it is on.
It can get working when I'm on the move, but as soon as I am still, it screws up. For instance, I can be driving to work and it works fine as far as telling me where I am at the moment. As soon as I close it and reopen it at work, it tells me I am somewhere 300-500 meters from work.
I guess I don't understand how it can work so well on the move, but as soon as I need an accurate reading, it is way off. Does this happen to anyone else?
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Once it's closed it loses the "Use GPS" setting and you have to turn that back on and wait for the Satellites to be located all over again.
Well i think there is a gps delay issue with the latest HTC phones as blackstone, Raphael and diamond and i believe there is a little on the x1. Well there will is always ways to tweak settings in the registry i guess. well you'll probably find something here at xda...
Ok, I see what you are saying...sa we speak, I am trying to get the location of where I am at on my phone. The status has been on "Seeking GPS satellites (0)" for about 3 minutes now. It just relocated my location nowhere near me.
Ok, I just got a message telling me that my "GPS receiver is having trouble tracking GPS satellites." It's a very clear night in southern California, no clouds, no trees, etc...If it is because I can't get a satellite, is there a way to configure it?
Can it be because I am inside my house? If so, that is absurd!
skotler said:
Ok, I see what you are saying...sa we speak, I am trying to get the location of where I am at on my phone. The status has been on "Seeking GPS satellites (0)" for about 3 minutes now. It just relocated my location nowhere near me.
Ok, I just got a message telling me that my "GPS receiver is having trouble tracking GPS satellites." It's a very clear night in southern California, no clouds, no trees, etc...If it is because I can't get a satellite, is there a way to configure it?
Can it be because I am inside my house? If so, that is absurd!
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Well i suggest you to go out and test it.. well also i suggest you to always keep your quick gps application updated so you'll get a quick fix locked to sattelites.. my Raphael locks on around 20-30 seconds and sometimes even less....
no problem here!
i've tested head to head with my old Asus P535 SirfIII (wich is pretty good as gps) on a 300km trip and they react in the same way.
no lag, no errors.
i use iGO8!
Well i found this on youtube: omnia vs HD in gps...
i am aware of that greek clip
what can i say? they have their experience, i have mine.
from my experience i say the gps of hd is good enough, as long as i don't make maps and i don't need precision on cm level
GPS works great on HD. Tested with IGO8 and latest TomTom, as well as Google Maps - all have accuracy within 5m range, wich is more then enough for normal navigation use.
I also tested my HD along side with Garmin car navigation unit - they were literary synchronized to the very second, even the voice instructions came at the same time, it was actually very funny
If you're having problems, I suggest you look up here on the forum for HTC GPS tool.
Well just to say, I agree with you guys eventhough i have a Raphael.. well i guess the gps chipset are the same.. (correct me if im wrong though) .. well many people in the Raphael community is talking about 50 - 100 yards lag but i only experience 5m, the most ive experienced was 10m but that was just once..
GPS doesn't work inside. Not just on the Touch HD but on any GPS device.
At the most, my lag is a car's length. I think my Trinity was slightly more accurated but not by much.
As far as getting a lock from inside, I can occaisionally get a lock if I am sat by my West facing window, but otherwise not a chance!
Ok, I got it working! I guess it just takes a couple minutes without touching any keys to acquire the satellites.
So in conclusion, to impatient people like me, don't touch any keys for a good minute or two. Thanks, guys!
HandGrip said:
GPS doesn't work inside. Not just on the Touch HD but on any GPS device.
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Mine does. Can take about a minute/minute and a half to lock to the satalites, usually finds about 9 of them, and from google maps when zoomed in to max you can see roughly where abouts in the house the handset is.
The cell tower lock is useless. I'm in the north west of england. The cell lock feature keeps telling me I'm in Russia!!
like all gps i have used, sometimes getting a fix is hard work, regardless of apparent sky conditions.... i guess thats what happens when technology (the gps sats) are made by the lowest bidder
if you have a "your postion within 300-500m" message displayed, then that is using the cell mast to get your position, you never see this message when using GPS
some progs and some roms prefer to have the gps ports mapped, i do it manually for all my gps progs using com4 and bit rate of 9600k... seems to offer best situation
afaik, no civilian GPS can assure an accuracy of greater then 15m, although some units some of the time seem to be more precise
i dont see lag, i see the limitations of GPS (outside of military application... but then again, we've seen how accurate smart bombs are not!!)
i always find that the GPS is very inaccurate. if i'm standing in my front yard it will show me a half mile out into the woods, with a few minutes of waiting, i can get it as close as 500ft away, but never the accuracy i find with a garmin GPS.
i remember with PSP i used the GPS Homebrew app MapThis, it always lowered the CPU clock speed automatically to prevent interference. with root, would lowering the X10 CPU increase the accuracy of the GPS?
lansingone said:
i always find that the GPS is very inaccurate. if i'm standing in my front yard it will show me a half mile out into the woods, with a few minutes of waiting, i can get it as close as 500ft away, but never the accuracy i find with a garmin GPS.
i remember with PSP i used the GPS Homebrew app MapThis, it always lowered the CPU clock speed automatically to prevent interference. with root, would lowering the X10 CPU increase the accuracy of the GPS?
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how many sats is it picking up ? are you surrounded by hills or high buildings or anything ?
mine can tell which corner of the garden im in and its not really a big garden either
it picks up sats very quickly too
also what firmware are you on ?
according to gps essentials, i have a lock with 6 satellites. the area i'm in has lots of woods and has a liitle bit of hills, and i'm running R2BA020 O2 version, on X10i
My GPS is incredibly accurate too...I'd say even faster than my Garmin.
My guess would be that you're just in an area with poor satellite reception. How accurate does it say your location is (like accurate to within what distance)?
Even on 3G with GPS off, my phone's accurate to within 500 feet.
GPS Status
Go to Android MArket and download an app called GPS Status. In it you can check sattelite reception, position and precision.
not trying to hijack your thread here but I live in Canada and im planning a long drive on Monday. Ive recently downloaded co-pilot and all the North American maps that go with it. Anyone have experience with this app, and also what happens when you move outside a 3g area? I would suspect that since you are using gps, and since the maps are downloaded that it wouldn't matter?? Just wondering if im right or not so I know what to expect on the road. Also, should I set the phone to never sleep / keep screen on while its plugged in throughout the drive? Its about a 13hr drive so im worried about keeping the phone on and plugged in that long. What are the opinions of others who have used this type of app?
brunswick000 said:
not trying to hijack your thread here but I live in Canada and im planning a long drive on Monday. Ive recently downloaded co-pilot and all the North American maps that go with it. Anyone have experience with this app, and also what happens when you move outside a 3g area? I would suspect that since you are using gps, and since the maps are downloaded that it wouldn't matter?? Just wondering if im right or not so I know what to expect on the road. Also, should I set the phone to never sleep / keep screen on while its plugged in throughout the drive? Its about a 13hr drive so im worried about keeping the phone on and plugged in that long. What are the opinions of others who have used this type of app?
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Its pretty accurate without 3g. I use it without any internet connection (3g/wifi) and it works well. Accurate about turning, etc. But im talking about walking.
I use Google Tracks all the time on my mountain bike and find it VERY accurate.
brunswick000 said:
not trying to hijack your thread here but I live in Canada and im planning a long drive on Monday. Ive recently downloaded co-pilot and all the North American maps that go with it. Anyone have experience with this app, and also what happens when you move outside a 3g area? I would suspect that since you are using gps, and since the maps are downloaded that it wouldn't matter?? Just wondering if im right or not so I know what to expect on the road. Also, should I set the phone to never sleep / keep screen on while its plugged in throughout the drive? Its about a 13hr drive so im worried about keeping the phone on and plugged in that long. What are the opinions of others who have used this type of app?
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Click to collapse
I do long drives from Vancouver down to Portland. Copilot has been very useful. Instant GPS lock even without a data plan. I never had to configure Copilot, it will always stay on when the program is on. Just plug your phone when the battery gets low
I believe it has something todo with the software / app you're using.
As I use the GPS with Google maps, it's surprisingly accurate and picks up movements as short as one single step in any direction right away and it is right on the spot where I stand according to reality.
I think your poor accuracy has nothing todo with the hardware anyway.
lansingone said:
i always find that the GPS is very inaccurate. if i'm standing in my front yard it will show me a half mile out into the woods, with a few minutes of waiting, i can get it as close as 500ft away, but never the accuracy i find with a garmin GPS.
i remember with PSP i used the GPS Homebrew app MapThis, it always lowered the CPU clock speed automatically to prevent interference. with root, would lowering the X10 CPU increase the accuracy of the GPS?
Click to expand...
Click to collapse
Honestly it sounds like your GPS location service is off and all that its getting is the wireless cell tower tracking. Try going into Settings-Location and check to see if GPS Satellites is enabled. It's probably off though by the sounds of it, or you have a faulty GPS receiver in your phone
yeah this phone seems to be less accurate than the x1, z1 gave me a 20 ft accuracy in the worst case and this one seems to be around 100 or even more :S
even my phone locates me on basketball ground whn im in home...approx 30m.....lol..
The bizarre 'wandering' behaviour leads me to suspect the navigation engine. When using a standalone GPS test app the Satellite lock I see is fine and the SNR (assuming it is being reported honestly) is OK.
In addition, when I'm using an app like Open GPSTracker I get convincing and accurate updates at around 1Hz (which is what you would expect) with a good solid position fix to within an accuracy I am happy with (usually 5-10m).
There are two issues I see:
First is that the speed reported by GPS apps is Bunk, or laggy at best. I haven't looked at the NMEA logs from the built-in GPS - do they contain accurate speed information?
Second is the 'wandering GPS' issue, which results in the classic continuing-straight-on-when-you-just-turned issue most of us are seeing.
This second issue, combined with the way you can observe the GPS reported position in something like Google Navigation slowly converging with the location you know you are are leads me to strongly suspect that Samsung are using some sort of IN/GPS mixing and doing it very badly.
GPS simply gives a position in its pure form. There's no interpolation or guessing at 1Hz (if you have GPS that advertises itself as a higher refresh rate then it probably is. but I assume the embedded GPS chip isn't too fancy and updates at a standard 1Hz). Usually the receiver then calculates the speed using a simple time/distance calculation between two points. Heading is simple geometry. Based in this fact I can think of no other explanation for the drifting behaviour.
What I suspect:
For some reason Samsung is mixing magnetometer and/or accelerometer data with the GPS positions (regardless of whether you select the 'use sensor data' option in the location menu), probably to avoid having to do the speed/direction computations from the raw GPS data alone or because their driver isn't providing it in the NMEA line (I assume that at some point the GPS chip provides a NMEA formatted output to the OS, this is that way every other device works!). In theory this should work really well and cut processing overhead - if you've got a good accelerometer giving acceleration and a good magnetometer giving heading why bother to calculate it from GPS position fixes, you can simply bias towards sensors and use the GPS for occasional updates.
However, while the MEM devices in the SGS while good enough for apps like Layar and Google Sky simply aren't up to the job of providing navigational quality mixing. I believe Samsung are being too clever and should re-write their positional engine using GPS position data alone and calculating speed and heading from that. It works for almost every other GPS device on the market.
At some point Samsung have tried to compensate for poor GPS performance by feeding sensors into the mix at the system level without user control. (I suppose this MIGHT be Googles fault??) This is giving a short-term bias towards interpolated positions fed from heading and accelerometer date which is provided by inaccurate sensors corrupting the perfectly good GPS information.
As I say, I don't know how good my guesses above are, it's simply an educated guess based on observation and some knowledge of IN/GPS mixing filters.
What do you guys think?
that's pretty much what i think but i dont have anyway to prove it
Well, standing still with walking directions with google Navigation I can see the zooming in and out
Pretty good assumptions there, dangrayorg. You might be spot on.
Sounds plausible. Of course the fundamental problem is probably poor GPS receiver and now Samsung is trying to work around that unfortunately with not to good results.
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.
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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.
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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..
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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..
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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..
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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..
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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
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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!!
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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
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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....
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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..
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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
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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?
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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
Hello users of Oneplus 5,
I would like to see a video how quick the gps locks (GPS ONLY)
Could somebody make a video of the app called gps test?
Bump
Could someone test this for me?
gps locked, drone strike incoming
MiszterSoul said:
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Thanks!!
Could you make a video without wifiand celliar connection. Soo reall offline
MiszterSoul said:
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Was this test done indoors or outdoors? I can't get a GPS lock AT.ALL indoors. Literally if I leave my OP5 plugged in and screen on for an hour, it still won't lock a GPS location (using GPS Status app) indoors. Indoors, near a huge window. My OP1 locks GPS in the same scenario in 15-30sec.
TornSack said:
Was this test done indoors or outdoors? I can't get a GPS lock AT.ALL indoors. Literally if I leave my OP5 plugged in and screen on for an hour, it still won't lock a GPS location (using GPS Status app) indoors. Indoors, near a huge window. My OP1 locks GPS in the same scenario in 15-30sec.
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"When it comes to indoors, however, GPS signals are typically marginal or unavailable because of signal lose caused by obstructions. A report from consulting firm Indoor LBS points out that the majority of the world's commerce and social interaction takes place indoors, yet can't take advantage of conventional outdoor GPS receivers. You can't use it to find your wife or kids at the mall. "
http://www.zdnet.com/article/getting-a-fix-on-indoor-gps/
it depends on a lot of stuff, even the weather can make a difference. i for my self get very quick a 8/27 fix indoors, but it still takes up to a minute to get the coordinates.
Hastaloego said:
"When it comes to indoors, however, GPS signals are typically marginal or unavailable because of signal lose caused by obstructions. A report from consulting firm Indoor LBS points out that the majority of the world's commerce and social interaction takes place indoors, yet can't take advantage of conventional outdoor GPS receivers. You can't use it to find your wife or kids at the mall. "
http://www.zdnet.com/article/getting-a-fix-on-indoor-gps/
it depends on a lot of stuff, even the weather can make a difference. i for my self get very quick a 8/27 fix indoors, but it still takes up to a minute to get the coordinates.
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My OnePlus 1 locks 5 satellites indoors in under 30 seconds with 10m accuracy. My OnePlus 5, on the other hand, can't lock a single satellite indoors; as a result, any app requesting location services perpetually cycles the GPS, or registers a location in a different part of the country. Even with bluetooth and wifi scanning enabled. It's off to the service center tomorrow.