Related
Hi,
I have been playing with the GPS Photo feature on ATT Tilt with HTC ROM.
I uploaded some of the pictures I took to locr.
The problem is the location on the map is about 50 ft. from the exact location where it should be.
However, TomTom seems to be displaying the location while driving pretty right.
I usually get signals from about 8-9 satellites.
I don't have much knowledge of GPS systems.
Is this something I should be concerned with (in terms of I paid a good amount for the pda, should I ask for a replacement), or is this error rate within acceptable limits? I think google map interface may not be too precise.
Thank you,
atakan said:
Hi,
I have been playing with the GPS Photo feature on ATT Tilt with HTC ROM.
I uploaded some of the pictures I took to locr.
The problem is the location on the map is about 50 ft. from the exact location where it should be.
However, TomTom seems to be displaying the location while driving pretty right.
I usually get signals from about 8-9 satellites.
I don't have much knowledge of GPS systems.
Is this something I should be concerned with (in terms of I paid a good amount for the pda, should I ask for a replacement), or is this error rate within acceptable limits? I think google map interface may not be too precise.
Thank you,
Click to expand...
Click to collapse
50ft does not sound overly excessive as an error. There are quite a few things that could affect the accuracy in relation to the photograph. Map accuracy being one but also how far away you are from the subject of the photo.
The GPS position on the photo is at best only ever going to be approximate as it will give the position of the photographer not the subject of the photo. So to give an extreme example, if I photgraph a mountain 3 miles away then clearly the GPS position attached to the photo will be out by at least 3 miles as it will log my position not the mountain's.
So the closer you are to the subject then the more accurate the position logged with the photo, but there will still be inacuracies. I generally find that GPS gives a better fix when you are moving. This is so because the software is able to extrapolate your direction of movement and the direction you are facing. This is not true when taking a still photo.
Mike
Hello Michael:
Thanks for your reply.
I actually took a chance with setting GpsGate parameters to parameters to COM4 and 57600 baud, and the error is now about 15 ft(5m). I didn't try other baud rates, but uploading pictures to locr displayed a location on the map closer to the location where I took the pictures of the ground.
atakan said:
Hello Michael:
Thanks for your reply.
I actually took a chance with setting GpsGate parameters to parameters to COM4 and 57600 baud, and the error is now about 15 ft(5m). I didn't try other baud rates, but uploading pictures to locr displayed a location on the map closer to the location where I took the pictures of the ground.
Click to expand...
Click to collapse
I think that's pretty good. Actually, as I understand it there may be limits imposed by the GPS set up in the Kaiser that mean the baud rate will not actually get up to 57600 despite it being set at that. However, 5m is as close as you could expect anyway I feel.
Mike
Tilt's GPS uses static navigation. That means that the GPS may not give you accurate positions if you don't move or you just walk. However, it works fine for higher speeds, such as driving. I don't really think that the baud rate affects if you change it to 57600.
dont forget it doesnt add like the .sec to the tag i think its just hours min. i havent looked at the photo info but if you look i think it doesnt tag the sec
atakan said:
Hi,
I have been playing with the GPS Photo feature on ATT Tilt with HTC ROM.
I uploaded some of the pictures I took to locr.
The problem is the location on the map is about 50 ft. from the exact location where it should be.
However, TomTom seems to be displaying the location while driving pretty right.
I usually get signals from about 8-9 satellites.
I don't have much knowledge of GPS systems.
Is this something I should be concerned with (in terms of I paid a good amount for the pda, should I ask for a replacement), or is this error rate within acceptable limits? I think google map interface may not be too precise.
Thank you,
Click to expand...
Click to collapse
All navigation software use some algorithm to "guess" where you are. If you GPS location is X feet from a recognized road, it assume you are driving on that road. When you are taking a picture, it can only give you the exact calculated location which can be off.
this is a dumb question. But what exactly is GPS photo? What i would assume is that it is where you take a picture of a landmark etc and you can put it at a loc on your maps so that it shows the pic while navigating?
But i don't like to assume, for obvious reasons!
Thanks for the help
alaiwy said:
this is a dumb question. But what exactly is GPS photo? What i would assume is that it is where you take a picture of a landmark etc and you can put it at a loc on your maps so that it shows the pic while navigating?
But i don't like to assume, for obvious reasons!
Thanks for the help
Click to expand...
Click to collapse
GPS photo is a function of the Kaiser which stamp the picture with the GPS location in the exif data.
What is wrong ? I`ve taken a GPS photo and inserted the figures from the photo into TOMTOM as a target and the result - the location is 10 km away from where I`ve taken the photo.
Any explanation ???
thanks
myrin
Two more things to keep in mind about GPS-photo:
First of all, Kaiser does not fill-up the GPS altitude tag, only latitude and longitude. Which, no doubt, will contribute to the cumulative error when displaying the position on the map. Also the coordinates are rounded to seconds, no fraction of second is noted. That's pretty bad idea
Second is much worse, Kaiser cannot properly edit gps-photos.
For instance the geotag is emptied when photos have been rotated from landscape to portrait and vice versa.
Here is an example of the geotag content:
GPS information: -
GPSVersionID - 2.2.0.0
GPSLatitudeRef - N
GPSLatitude - 51 25 11.00
GPSLongitudeRef - E
GPSLongitude - 5 27 56.00
GPSAltitudeRef - Sea level
GPSAltitude - 0 m
GPSTimeStamp - 23 13 32
Click to expand...
Click to collapse
But according to TomTom my
GPSAltitude - was 82 meters above the sea level.
GPSLatitude - 51 25 11.89
GPSLongitude - 5 27 56.65
So honestly I don't see how increasing the baud rate of the GPS gate could possibly improve the precision.
gps cursor molving around
I have been using google maps with my Tilt (original rom) for a couple weeks and the location was always spot on. i'd zoom in as close as i could, for example, at a friend's house and you could see the flashing dot hovering over the roof - right on top of where we were standing.
however . . . today i downloaded the taster version of tom tom and downloaded the free map for chicago. the location it showed for me was a good 2 city blocks west of where i was standing. that is about 400 meters maybe (i'm bad with distances, but it was far). i switched to google maps and it showed my location at the same erroneous spot.
after turning my device on and off and re-downloading the latest sat info with Quick GPS the locator in google maps started to edge east to where i was. i was happy to see that. after about 5 minutes, the cursor was over my office. but then it kept going accross the street. then it hovered back and a little south. now it is within 30 meters of my exact location, but it is constantly moving around within that 30 meter circle. it is no longer as precise as it once was.
i never noticed this happening on google maps before. could there be some issue now that i have downloaded tom tom?
MAXPOW3R said:
i never noticed this happening on google maps before. could there be some issue now that i have downloaded tom tom?
Click to expand...
Click to collapse
I don't think it has anything to do with tomtom.
Please go to the place you know, find it in Google Earth and make a GPS photo of the spot. Than take normal photo of the same place and Geotag it with Google Earth.
When you compare EXIF data of both photos you will know what's wrong with Kaiser
Contrary if you use software that can properly handle the info read from GPS reciever then your location will be displayed within few meters.
Here is example of my trip around the neighborhood
http://tracker1.reperion.com/GMap.aspx?name=BARMALINI&Gzoom=2&mStyle=G_HYBRID_TYPE&PPON=true
As you can see, green balloons always placed along the road, with max deviation of about 10-15 meters and the speed of the car was always determined correctly. The only reason for this improved precision is that the software that I used for tracking is less buggy than the GPS camera.
be happy its not showing you that the photo was taken in Kazakstan. one other member and myself are getting positions in another country.
barmalini said:
I don't think it has anything to do with tomtom.
Please go to the place you know, find it in Google Earth and make a GPS photo of the spot. Than take normal photo of the same place and Geotag it with Google Earth.
When you compare EXIF data of both photos you will know what's wrong with Kaiser
Contrary if you use software that can properly handle the info read from GPS reciever then your location will be displayed within few meters.
Here is example of my trip around the neighborhood
http://tracker1.reperion.com/GMap.aspx?name=BARMALINI&Gzoom=2&mStyle=G_HYBRID_TYPE&PPON=true
As you can see, green balloons always placed along the road, with max deviation of about 10-15 meters and the speed of the car was always determined correctly. The only reason for this improved precision is that the software that I used for tracking is less buggy than the GPS camera.
Click to expand...
Click to collapse
thank you for your suggestion. i'm not sure how to take GPS photos, but i will look into it. I saw this thread was about how precise the GPS was and thought I would ask my question here. My cursor seems to move around the screen a lot now and it did not do that before. it sort of drifts around a 30 meter radius of where I actually am. i can see it moving around even when i am sitting still. I just noticed the problem yesterday after installing tom tom, so i thought maybe there was a connection. wish i could figure this out.
im considering buying this phone,but i hear there's problems with the GPS. my current phone has a great GPS receiver and i use it a lot for day to day navigation.How much will i be disappointed if i were to expect the same from the galaxy s?
http://forum.xda-developers.com/search.php?searchid=42858169
Here in holland I have no problems with the GPS reception...
Personally, I found that straight out of the box the gps was dreadful, but an hour later after I did the simple gps fix, it navigated me on a hundred and fifty mile round trip with no problems at all.
The fix is simple and easy and takes literally no skill. When you take your sgs out of the box, see if the gps works for you, then try the fix. If there is still no joy then take it back and say the navigation is busted and you want a different handset.
I'd certainly say its worth trying at least. Chances are can get it working and everything else that you like about droid is better on the galaxy .
It's worth remembering that the gps is not battery friendly and you'll need a potent (2A output)car charger to keep you running on the move.
Sent from my GT-I9000 using XDA App
Basically, in summary:
1) In late firmware, the lock is quite quick, especially compared to car GPS units. Maybe not as fast as some other phones, but fast enough. Certainly faster than my Garmin Forerunner
2) The accuracy boundaries on this phone are wrong sometimes (at least in XXJM5), but this may be a bug in that specific pre-release.
3) With JM5, the unit seems to only lock onto 8 satellites max, but, some people are saying apparently newer firmware's are locking onto more
4) People are complaining of issues getting locks when moving with the unit. However, I've experienced this on ALL GPS units I've owned. AGPS should help with this though (but I've never tested initial lock whilst moving except in a firmware where GPS was 100% broken for me).
5) In some cases, the GPS goes skitzo, this might be fixed in later firmwares
6) Finally, sometimes the track is a bit off to the side, and doesn't handle cornering well.. This is likely related to (2). But this makes it useless for fitness at the moment
Anyway, the GPS is usable, but there are serious accuracy problems with it still. Samsung has said that they are working on optimising GPS for a September update. My best advice is wait until then, because if it isn't fixed in September, the possibility that it is due to poor hardware design seems to grow significantly..
thank you for your valuable input,this forum really is the best on the internet.I'm gunna be buying it next month anyway,so lets see if the update fixes the GPS or not.To be honest,theres no other phone that can match it,so theres no alternative to this phone even if the GPS IS dodgy
The GPS sucks so hard that I'd rather use a regular map for navigation.
My Galaxy S has no gps problems. The first time i went out from house to check GPS accuracy I got GPS signal after 3 seconds. It's stable in 100% cases.
Acquiring signal is not the issue. I don't understand why people keep comparing signal to accuracy. it's not the same thing.
Exactly, there are people in other topics that are just inflating the whole issue, their claims are way exaggerated, and the original issues has already been fixed on newer firmwares, yet they refuse to accept it.
AllGamer said:
Exactly, there are people in other topics that are just inflating the whole issue, their claims are way exaggerated, and the original issues has already been fixed on newer firmwares, yet they refuse to accept it.
Click to expand...
Click to collapse
Go for a 20min jog then and show a track of your perfect GPS. I have a lower standard than many of them, but all tracks I saw lost lock excessively at some point or another..
I haven't tried it myself, but can on tuesday.
damn,so many different opinions on this issue.also not being able to track my runs is a BIG minus but still not a deal breaker.day-to-day city navigation is a must though.
It's just as simple as that - you don't check gps functionality just by its fix time. you put it in your car, and start driving - if it's accurate (highly unlikely), gewd. if not - go back here and whine.
kingofkings2603 said:
damn,so many different opinions on this issue.also not being able to track my runs is a BIG minus but still not a deal breaker.day-to-day city navigation is a must though.
Click to expand...
Click to collapse
The big problem is that many of them seem to be testing quickly from their chair.. There is overwhelming evidence that the GPS doesn't work accurately, but barely any showing it does.. In fact, in one case, I saw someone claim the unit was working perfectly, but the track they showed was on a straight highway, and was fluctuating excessively between both sides of the highway. And the most vocal of those who claims it works perfectly don't seem to be posting logs..
There is also some confusion between whether it is "fitness grade" or "car grade". Car navigation GPS can snap to tracks, and has more room for accuracy errors, because it can assume you always exist on the closest road, and if you use directions, it can assume you took the correct turns when it told you to do so (and correct itself a bit later). That's what most car units seem to do, and it helps compensate for most inaccuracies. It can lead to a bit of pain though if you make lots of turns, some of which aren't correct. Some people are possibly happy because they have used dedicated car units before which suck (some navman's take at least 5 mins to get a basic lock, negating any benefits of having them), but, since some phones offer better directions apparently, people are complaining it should be better.
Fitness grade requires MUCH higher resolution to be usable, because the distance is shorter (generally), and if your GPS veers off course, it gives you a false indication of jogging distance. Garmin forerunners feel generally like they are within 1 or 2 meters a of the time (but occasionally veers off 3), but from what I've observed standing still, the flaws may be less visible when moving, but simply appear as slightly off course.
Then there are those people who stare at the SNR/locked satelites for hours at end without checking whether the long/lat is actually correct, or the accuracy boundary (they see 5m accuracy, but don't actually check if it is accurate within 5 meters). I was one of these, until I realised that the accuracy boundary was wrong..
Part of the issue also comes down to firmware though. People are using pre-release/leaked firmware (which might not even be complete) and are judging the GPS quality based on that. No comment needed except, don't assume that Samsung aren't working on fixes because there is no fix in pre-release firmware.
I haven't properly tested either though personally because I use a forerunner for jogging (waterproof), and since I fly, I prefer to use maps to understand locations better. I did notice though that leaving my phone on my desk for a long period of time sometimes allowed the signal accuracy boundary to not include me (ie, allow a position of 20m away from me, but show 5m accuracy) intermittently. And this might explain the fluctuations in position many others have gotten..
Either way, it is debatable. The biggest issue is that the assumption so far is that everyone got exactly the same hardware, and exactly the same revisions. But the other problem, is that GPS quality is open to opinion, because in some areas, roads are so far spread out that even inaccurate GPS works fine for driving. It really depends on your needs. But the facts are, the accuracy of the GPS isn't worth debating anyway currently, because Samsung have already told us they are "optimising" the GPS in Sept, which may make this unit as good as a garmin forerunner anyway. All any of us can tell you as that we'll know the TRUE potential of the unit after the september patch.
But for me anyway, I think the GPS is fine (I don't need perfect accuracy, even if I needed this as a fallback in a plane)
The GPS is bad to the point of being unusable for car navigation or fitness tracking. Yes you may get a lock in GGps test but when moving the reported location is all ov
er the place.
andrewluecke said:
Then there are those people who stare at the SNR/locked satelites for hours at end without checking whether the long/lat is actually correct, or the accuracy boundary (they see 5m accuracy, but don't actually check if it is accurate within 5 meters). I was one of these, until I realised that the accuracy boundary was wrong..
Click to expand...
Click to collapse
Case in point to illustrate what andrewluecke is trying to explain here about the accuracy not being exactly...well, accurate. Take a look at the attached screenshot. My GPS had a great fix with accuracy of 5m (the best it's able to report), stable for a few minutes, everything was working perfectly. Or so it seems. Except for the slight problem that I was actually standing where the red dot is... There's no scale on the screenshot, but it's a good 30-40 meters off. And that's quite common for me.
Case_ said:
Case in point to illustrate what andrewluecke is trying to explain here about the accuracy not being exactly...well, accurate. Take a look at the attached screenshot. My GPS had a great fix with accuracy of 5m (the best it's able to report), stable for a few minutes, everything was working perfectly. Or so it seems. Except for the slight problem that I was actually standing where the red dot is... There's no scale on the screenshot, but it's a good 30-40 meters off. And that's quite common for me.
Click to expand...
Click to collapse
Exactly Case_. The point of the accuracy measurement is to say "you are somewhere within this range". But, with the Galaxy S, it isn't, and that shouldn't happen, at least not as often as it does (except maybe at the beginning whilst obtaining a lock"). Professional systems have something known as RAIM and FDE which detect when the accuracy may be incorrect due to external factors (such as shonky satelite, or serious atmospheric interference). But this happens a LOT, and I would have thought it affects GPS units equally (unless the Garmin forerunners in fact DO ship with fault detection, which could explain it, in which case, Samsung should implement fault detection and exclusion too, to make it usable).
Anyway.. What I am trying to say is summed up easiest with Case's post.
Fatherboard said:
Acquiring signal is not the issue. I don't understand why people keep comparing signal to accuracy. it's not the same thing.
Click to expand...
Click to collapse
It most certainly is an issue. It takes a minute or longer to acquire a lock in some cases despite stationary and clear line of sight.
The people who stomp their feet with "The GPS is fine" are no different than the iPhone4 users who claim there is no attenuation in their phones.
In my case with the DDJG4 update, I see some minor issues.
Once in a while when I am at home (indoors with no visible satelites) my location shifts from bangalore to toronto. All my stuff changes to that. It looks like AGPS is not turned on or buggy becuase 80% of the times it works well. Does anybody else face the same problem ?
So when my phone takes me to toronto, i restart the phone and everythng is back to normal
SOmetimes, the location service fails to find where I am and shows Toronto in Google website. Is there anyway to avoid this.
It's just like what most people say, you can get a fix, and GPS seems fine. Try to use it, and it's a whole different story.
Somebody on the forum posted a link of a run, where the SGS GPS went everywere but on the straight line, it even made a hilarious loop. Too bad i can't find it.
People need to stop saying "Firmware updates fixed it already" as that's just not true.
Hah, there it is, posted by sjdean.
Desire, and SGS GPS.
http://maps.google.com/maps/ms?ie=U...52.48542,-1.742063&spn=0.014138,0.045319&z=15
http://maps.google.com/maps/ms?ie=U...=52.48082,-1.761761&spn=0.01414,0.045319&z=15
I have been hearing of numerous complaints about the GPS of the Galaxy S and was wondering if mine had an issue.
Having only GPS'd my location at a standstill with excellent (within 10 metre) results, I decided to use Google Navigation on a 15 kilometre trip from where I was to my home.
I can honestly say my GPS had pinpoint accuracy for the entire trip, not losing signal once. And when I mean pinpoint accuracy, I mean it felt like a satellite was right on top of me the entire way home.
Apart from Google Navigation using a weird route to get home (which I followed, only forcing the unit to reroute once), and speaking the street names like it didn't understand grammer, I'd say it was almost as perfect as my tried and true Garmin (which uses better routes).
So this isn't a gloating post, but I'm trying to understand what issues all of you have with the GPS, as I don't seem to be experiencing any.
P.S. I'm still on Bell's official 2.1 firmware (latest one, I believe its JH2).
Thanks
Go for a walk. Stop for a coffee somewhere. Walk again. Stop to enjoy something beautiful. Record your experience with My Tracks. Share you track. Then we can discuss GPS quality.
I hope it all works excellent for you.
Regards!
Sent from my GT-I9000 using XDA App
Nice story but why post it as a [Q] and in development forum
NetCopAD said:
Go for a walk. Stop for a coffee somewhere. Walk again. Stop to enjoy something beautiful. Record your experience with My Tracks. Share you track. Then we can discuss GPS quality.
I hope it all works excellent for you.
Regards!
Sent from my GT-I9000 using XDA App
Click to expand...
Click to collapse
Ditto. 10 char.
NetCopAD said:
Go for a walk. Stop for a coffee somewhere. Walk again. Stop to enjoy something beautiful. Record your experience with My Tracks. Share you track. Then we can discuss GPS quality.
I hope it all works excellent for you.
Regards!
Sent from my GT-I9000 using XDA App
Click to expand...
Click to collapse
Ok, I never really use my GPS that way, but for experimental purposes I will. Downloading the program now (not factory software with Bell I guess). Is there a certain distance I should be walking? And what should I notice to report back? That my tracks were the exact route I took?
Having said that, if there is a problem, could it not be a specific problem with the way MyTracks itself cooperates with the GPS? I mean I find it strange the GPS works flawlessly with Navigation (stops and lights, stop signs etc) but not with My Tracks? I dunno.
gllu said:
Nice story but why post it as a [Q] and in development forum
Click to expand...
Click to collapse
You're right.. didn't realize I posted it here until after I posted it. I leave the moderating for moderators, but my apologies just the same. Moderators, please move this to an area which is more suitable to avoid posts like these.
greeced said:
Ok, I never really use my GPS that way, but for experimental purposes I will. Downloading the program now (not factory software with Bell I guess). Is there a certain distance I should be walking? And what should I notice to report back? That my tracks were the exact route I took?
Having said that, if there is a problem, could it not be a specific problem with the way MyTracks itself cooperates with the GPS? I mean I find it strange the GPS works flawlessly with Navigation (stops and lights, stop signs etc) but not with My Tracks? I dunno.
Click to expand...
Click to collapse
Not just My Tracks, you can try any other similar apps. That's just the most popular and widely used one.
The thing with Navigation is, it KNOWS you're supposed to be travelling on the road - so even if the actual GPS data suggests that you're 5 meters off the road, the navigation software "corrects" it and puts you back on the road.
Use My Tracks to record a small walk. Make a couple of stops. It ALWAYS puts me 15 feet off the road. And when standing still, it keeps moving around restlessly. Ugh
It's just that navigation software generally has the ability to use road information to supplement the raw GPS data and thus yields seemingly better results. It snaps to roads, approximates expected position etc.
My Tracks and other similar software just records your track without any awareness of roads so the resulting info (track) is pretty close to the raw GPS performance.
Standing still is when the GPS problem is most evident. Your reported position just jumps around, sometimes sending you a hundred meters away or more.
Sent from my GT-I9000 using XDA App
Ok,
Went for a short walk using my tracks... Around a rather large block and through a path in a park, where I sat down on a park bench for 5 minutes, got up, and continued the trail back to the main road, then back to my house.
I noticed when I started off, it showed me on the other side of the street, but quickly corrected itself as soon as I started walking to the right side of the street.
I then stopped at a communal mail box, I noticed the gps had 'bounced' to the other side of the street but as soon as I started walking again, it corrected itself.
The other side of the street on those two occasions was 15-20 feet away (Its a residential side-street), which to me has the GPS as being extremely accurate. Even Google's disclaimer on "My Tracks" states:
Under optimal conditions the location can be +/- 20 feet (6 meters).
And thats exactly what it was with mine.
After the communal mail box, it was extremely accurate to less than 2 metres the rest of the trip/way home. The circle around the orange arrow was extremely small most of the way, only getting larger when I entered my house.
NetCopAD said:
It's just that navigation software generally has the ability to use road information to supplement the raw GPS data and thus yields seemingly better results. It snaps to roads, approximates expected position etc.
My Tracks and other similar software just records your track without any awareness of roads so the resulting info (track) is pretty close to the raw GPS performance.
Standing still is when the GPS problem is most evident. Your reported position just jumps around, sometimes sending you a hundred meters away or more.
Sent from my GT-I9000 using XDA App
Click to expand...
Click to collapse
See, standing still with me is absolutely bang on within 10 metres. If you're talking about when you first fire up the GPS, then I'd agree with you, but the hundreds of metres away is not your GPS position. Its where your cell provider is reporting you to be, either by the tower, or triangulation.
The GPS then using that information, as per my guess, to hone on where you are. and it actually finds me within 5 to 10 seconds.
Oh and as for navigation, I'd have to disagree with your assertion about the GPS and the knowing your on a road statement. I live in an area where new roads are built all the time, and those roads are not on any mapping system including garmins, and the GPS will follow you anyway, just go into a constant cycle of
"Recalculating" or "Turn Around" or "Make a U-Turn". (At least that's what my garmin does when I test it), but it still follows me up to and including the road that is actually on the GPS, and I'm sure this GPS will do the same.
Either way, I'm happy that I don't have any issues with the GPS of this Galaxy S. Seems to work quite well.
same here, once i intentionally drove into this field of newly paved road, with no houses foundation even build on them, it was so funny to see myself on google map going into what seems like an empty space
but with the tracking enable, it was able to draw good lines of where i drove over for the missing streets on the map
greeced said:
Oh and as for navigation, I'd have to disagree with your assertion about the GPS and the knowing your on a road statement. I live in an area where new roads are built all the time, and those roads are not on any mapping system including garmins, and the GPS will follow you anyway, just go into a constant cycle of
"Recalculating" or "Turn Around" or "Make a U-Turn". (At least that's what my garmin does when I test it), but it still follows me up to and including the road that is actually on the GPS, and I'm sure this GPS will do the same.
Either way, I'm happy that I don't have any issues with the GPS of this Galaxy S. Seems to work quite well.
Click to expand...
Click to collapse
Ok..this is going to be a little long-winded so bear with me.
So there seems to be a new fix posted for gps every other day, some are just snake-oil while others might actually be doing something. The problem is how to tell what is working and what is not...and to what degree. Trusting the word of some guy on a forum with 200 posts is NOT the answer. What we need are some objective tests that produce quantitative data. It would also be nice to objectively compare our device's performance to the performance of other android devices out there too...to get an idea of what a realistic gps performance expectation would be.
So far MyTracks seems to have been the best approach but it's still a very poor method for several reasons:
The software acts as an abstraction layer - it's unknown what kind of filtering may be occurring here.
The data is only meaningful to the originator; we don't know which street(s) you were really on.
At best only 1 dimension of the error is preserved; we might be able to assume you were driving down street X, but how do we know how far down the street you actually were when the sample was captured?
Bottom line, there is no way to programmatically extract quantitative results.
I've got half of the solution: Collect a series of samples from a stationary position and collect lat/lon/alt/time, reported gps accuracy, number of satellites used, time to lock, device make/mode, device uptime (to weed out the "I rebooted and it works!" phenomenon) etc.
With this data we can calculate things like jitter, deviation, acquisition latency and all kinds of other interesting things.
I know that sounds like lots of work, but I've already done all of the above (scroll down to the bottom to read more about that) and for the most part the data collection and result presentation components work. The problems I am running into are related to the details of how the above data maps to real world performance.
So let's talk about some potential algorithms:
1. Deviation
This was my first hope as a solution; grab bunch of gps coordinates and use the lat/lon positions along with reported accuracy to get a centroid location. Then using the centroid, calculate the distances between each point and the centroid to measure accuracy. In theory, if the distribution was random, this would work. In practice however, I found that:
A - You get A LOT of duplicate points that throw off the statistics.
B - Even if you throw out duplicates, the coordinates you get are usually very close to one another, in spite of being far from the true location. In hindsight, I think that should have been obvious. Oh well.
In any case, let me illustrate:
I took 30 samples sitting in front of my office. The distribution looks like this:
http://maps.google.com/maps/api/staticmap?size=512x512&maptype=hybrid&markers=color:blue|label:1|37.280015489448,-121.943445407709&markers=color:blue|label:2|37.280015489448,-121.943445407709&markers=color:blue|label:3|37.2799150689755,-121.943469689324&markers=color:blue|label:4|37.2798287737251,-121.943507481842&markers=color:blue|label:5|37.2797409130025,-121.943532462122&markers=color:blue|label:6|37.2796490544446,-121.94354159922&markers=color:blue|label:7|37.2796117648545,-121.943468886907&markers=color:blue|label:8|37.2796034813727,-121.943455640717&markers=color:blue|label:9|37.2795946561935,-121.94344227994&markers=color:blue|label:10|37.2795861462627,-121.943431154687&markers=color:blue|label:11|37.2795786087998,-121.94342342341&markers=color:blue|label:12|37.2795720667083,-121.943418240036&sensor=false&sensor=false
And the centroid I calculated from these looks like this:
http://maps.google.com/maps/api/sta...7,-121.943465819874&sensor=false&sensor=false
Looks pretty good so far right? Not even close. You can almost predict where the gps will say I am going to be next just by looking at those points. Unfortunately, there's no data there about where I actually am. I was actually standing outside of the building, smack in the middle, which is about 30 meters south of the closest sample I got.
Which brought me to idea #2:
Measure reported accuracy, sampling frequency/jitter, time it took to acquire the initial lock and call it a day.
Which brings me here - I'd like to do this right and so I'd love to get anybody's feedback on what kind of algorithm to use to characterize gps performance.
Also, if anybody wants to take a peek at whats been done so far, here's a link to a page with the latest version of the android client. Just install it and start it up. It will pop up and error if it can't connect to the server and the server does go down from time to time, so if you get a connection error, try again a little later. The other thing to be aware of is that I enforce the "stationary collection" rule by monitoring the accelerometer. When you hit start you will have 3 seconds to put your phone on a table or the sidewalk or somewhere else that isn't moving. Once the collection starts, it will monitor GPS until it gets 30 samples. You can cancel at any time by moving the phone. If any samples were collected, they will be uploaded and you will get an option to view the results. The results aren't too terribly meaningful for now, but there are a couple interesting statistics there and you will be helping me out by stress testing the server. Feedback appreciated!
Thx
The only problem is I believe there may be some hardware variation. I've read some posts where they took two completely identical stock phones and got completely different results.
I don't see a problem with stationary data. It will always jump around. That's hardware. The hardware cannot accurately track anything less than 10 meters.
I'm more worried about why it's jumping around and losing accuracy when it's in motion.
I would make a data collection for TTTF , satellites in view, satellites with fixed, signal strength (SNR), bearing, hasAlmanac(), hasEphemeris() and accuracy.
I was thinking of writing an app but I really don't have the time for it. I have a bunch of projects lined up and really won't see any real free time until a month or two. I program for a living and currently have a private android application that uses GPS that I wrote for my clients. It's a shame the GPS is borked with the Galaxy S because I was going to use it to market my application. I have to resort to the Xperia X10. My interest in fixing the GPS is both personal and business related.
Regardless, if you need any help, let me know.
PS: I believe we need a program to really compare our "fixes" and narrow down what changes makes things better and worse. I would like to get to the point where we can calculate: X # of satellites with an average of Y dbHZ of signal strength gives you Z% accuracy
ThisWasATriumph said:
The only problem is I believe there may be some hardware variation. I've read some posts where they took two completely identical stock phones and got completely different results.
Click to expand...
Click to collapse
I dont really think that the variations are hardware related, at least I've not seen any solid data to support that assertion. Different results, even wildly different between two identical phones is expected to some degree...theres too many variables involved to directly compare two phones and expect to get identical results, even side by side. For instance, reboot one of the phones and try again. The rebooted phone will have much better performance. If we get some averages based on device and software version / configuration with a large number of samples behind it, actual differences should emerge from the noise. In any case, if there truely is a hardware problem, that will probably also be discoverable as an abnormally high standard deviation compared to other devices.
CLShortFuse said:
I don't see a problem with stationary data. It will always jump around. That's hardware. The hardware cannot accurately track anything less than 10 meters.
I'm more worried about why it's jumping around and losing accuracy when it's in motion.
Click to expand...
Click to collapse
In theory, there shouldnt be any functional difference between a moving receiver and a stationary one. At least over relatively short distances. Yes one will be cross cutting various geometric relationships with the satellites, but they are so minute that its a moot point.
On top of that, benchmarking while moving introduces two problems:
1 - Telephone poles, buildings etc. Will periodically obstruct the signal introducing an error that cannot be subtracted out.
2 - As mentioned above, there is no known point of origin. One of the consequences of that is that the conditions surrounding the data collection of user A can vary wildly from those of user B. In essence you stop measuring performance alone and start measuring performance plus the dynamics of the neighborhood. With a stationary position at least you know that your gps shouldnt be showing you moving.
From my own testing, I can say that the Captivate typically does not even calculate stationary locations correctly, as seen in the links posted above. Sadly the error signal bears no obvious relation to the true origin. And although there is a definite pattern I don't know how to analyze that pattern. I'm humble enough to admit that I'm not smart enough to figure it out. Hopefully somebody else here is though At the very least, I think that the error patterns generated from a stationary position are a solid basis for a standard test.
You should try cognition 2.2 with CLShortfuse's jupiter tweaks. For the first time I was driving 55mph with 9-11/11 sats locked on the whole time, kept an accuracy of 5-10 meters and it accurately reported my speed dead on with my speedometer. I'm pretty satisfied with the performance right now.
Have you done any tests at a benchmark site to see how accurate it is? I have been at a benchmark site one day and gotten really accurate results, only to return on another day and have trouble getting within 300 ft. accuracy. And this was done with a "real" GPS.... I think that it is going to be difficult to get good results with a smart phone acting as a handheld GPS device. Maybe I am wrong ..... I'm no engineer or programmer...
Sent from my custom EVO PC36100 Using XDA app
halfhp said:
From my own testing, I can say that the Captivate typically does not even calculate stationary locations correctly, as seen in the links posted above. Sadly the error signal bears no obvious relation to the true origin. And although there is a definite pattern I don't know how to analyze that pattern. I'm humble enough to admit that I'm not smart enough to figure it out. Hopefully somebody else here is though At the very least, I think that the error patterns generated from a stationary position are a solid basis for a standard test.
Click to expand...
Click to collapse
I haven't taken a look at your program but collecting mass amounts of information is a start. We can draw a correlation between signal strength, # of antenna and accuracy.
There is another option, that I believe would be best to identify the underlying issue. Have different Android GPS units side by side both running the same application, and have them report data for each satellite (based on PRN). They SHOULD be identical (azimuth, elevation and if possible, the reported time). Also, we would check the system times and see if they are synchronized.
According to Garmin:
Sources of GPS signal errors
Factors that can degrade the GPS signal and thus affect accuracy include the following:
Ionosphere and troposphere delays - The satellite signal slows as it passes through the atmosphere. The GPS system uses a built-in model that calculates an average amount of delay to partially correct for this type of error.
Signal multipath - This occurs when the GPS signal is reflected off objects such as tall buildings or large rock surfaces before it reaches the receiver. This increases the travel time of the signal, thereby causing errors.
Receiver clock errors - A receiver's built-in clock is not as accurate as the atomic clocks onboard the GPS satellites. Therefore, it may have very slight timing errors.
Orbital errors - Also known as ephemeris errors, these are inaccuracies of the satellite's reported location.
Number of satellites visible - The more satellites a GPS receiver can "see," the better the accuracy. Buildings, terrain, electronic interference, or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. GPS units typically will not work indoors, underwater or underground.
Satellite geometry/shading - This refers to the relative position of the satellites at any given time. Ideal satellite geometry exists when the satellites are located at wide angles relative to each other. Poor geometry results when the satellites are located in a line or in a tight grouping.
Intentional degradation of the satellite signal - Selective Availability (SA) is an intentional degradation of the signal once imposed by the U.S. Department of Defense. SA was intended to prevent military adversaries from using the highly accurate GPS signals. The government turned off SA in May 2000, which significantly improved the accuracy of civilian GPS receivers.
Click to expand...
Click to collapse
rtdrumz said:
Have you done any tests at a benchmark site to see how accurate it is? I have been at a benchmark site one day and gotten really accurate results, only to return on another day and have trouble getting within 300 ft. accuracy. And this was done with a "real" GPS.... I think that it is going to be difficult to get good results with a smart phone acting as a handheld GPS device. Maybe I am wrong ..... I'm no engineer or programmer...
Sent from my custom EVO PC36100 Using XDA app
Click to expand...
Click to collapse
I have neither used nor heard of gps benchmark sites - do you have any that you've used that you recommend?
I'm fully expecting the variance you are talking about, but I also believe that the variance is there because of measurable variables...it's just a matter of identifying enough of those variables to make the results understandable. For example, we know a reboot can temporarily fix gps issues so we wouldnt want to compare the gps results of a device that was just rebooted with the results of one that has been running for days.
CLShortFuse said:
There is another option, that I believe would be best to identify the underlying issue. Have different Android GPS units side by side both running the same application, and have them report data for each satellite (based on PRN). They SHOULD be identical (azimuth, elevation and if possible, the reported time). Also, we would check the system times and see if they are synchronized.
According to Garmin:
Click to expand...
Click to collapse
I briefly started down that road by grabbing the raw NMEA sentences but quickly abandoned that path due to the volume of data being pumped. Maybe I should take a second look.
Regarding the dual phone test, thats an interesting idea. I wouldnt have expected the clock times to vary at all. I'll check into it!
Also, for whoever is interested, here is a link to some results generated by the app in progress:
http://www.halfhp.com:8080/ggs/results/show/1?mode=mobile
It only shows a small subset of the data collected, but you get the general idea of what I'm going for.
I disabled the automatic time sync. I'm going to look for an app to synchronize my clock. I'm going to disable AGPS and take a test run. It could be wrong timing that makes it unable to grab a fix
WOW, talk about a difference. I disabled time sync and I used an application called "Micro Second".
Clock difference: 5.41638 seconds
That GPS trailing/sliding issue seems about 5 seconds as well......
CLShortFuse said:
I disabled the automatic time sync. I'm going to look for an app to synchronize my clock. I'm going to disable AGPS and take a test run. It could be wrong timing that makes it unable to grab a fix
Click to expand...
Click to collapse
Shouldnt the chip be keeping track of it's own time? One common use of gps is to provide a time signal accurate to the microsecond. As far as I know, all gps devices are capable of that kind of accuracy - they have to be in order to work at all, they just dont advertise it because many dont provide a physical interface to the PPS necessary for external devices to utilize it.
halfhp said:
Shouldnt the chip be keeping track of it's own time? One common use of gps is to provide a time signal accurate to the microsecond. As far as I know, all gps devices are capable of that kind of accuracy - they have to be in order to work at all, they just dont advertise it because many dont provide a physical interface to the PPS necessary for external devices to utilize it.
Click to expand...
Click to collapse
"Should" and "does" aren't the same thing. That's under the assumption that the NMEA data is provided by gps device itself. I don't believe it is. I think the GPS device gives raw satellite data and the driver wrapper calculates NMEA data back to Android.
Also, factoring the clock desync from the correct atomic-based time should be in the data.
CLShortFuse said:
"Should" and "does" aren't the same thing. That's under the assumption that the NMEA data is provided by gps device itself. I don't believe it is. I think the GPS device gives raw satellite data and the driver wrapper calculates NMEA data back to Android.
Also, factoring the clock desync from the correct atomic-based time should be in the data.
Click to expand...
Click to collapse
I think you might be at least partially right as far as the NMEA sentences being generated outside the chip. I did a little bit of digging on the BCM4751 chip and it appears that the protocol used is MEIF, which according to the internet is a proprietary nokia protocol. I havn't found a description of the protocol yet, but I would think that it offers at least the same amount of data that NMEA offers, meaning time is kept on-chip as expected. I just cant imagine the system clock being anywhere close to useable for such a time sensitive calculation as gps triangulation. I'm gonna keep looking though.
Something else to consider guys...
I've seen lots of people referencing GPS accuracy when in motion versus standing still. I'm not so sure that all of them are complaining about what they think they're complaining about.
My primary vehicle is a motorcycle. For crappy weather, I've got a Jeep Wrangler with a fiberglass hardtop. In both cases, the phone has no sheet metal between it and the sky. And in both cases, the GPS appears to track just fine. It may not show me in the proper lane of a multilane highway, but it at least always shows me on the right side of the road, and it never lags behind my actual position. Nor does it suffer from any 'inertia' problems. When I turn, so does it. When I stop, it does too.
Now... I'm out of town at the moment on a business trip and am driving a rental car - one with a fixed sheet metal roof (no sunroof either). Since my GPS had been working at home, I was expecting it to work over here as well. Wrong! It takes forever to get a lock, and when it finally does, it drifts in and out of lock. And as I'm driving along, it's sometimes as much as 5 seconds behind me. Or sometimes along side me on a side street. Or when I stop it keeps going. You know, all the crap that everybody's been complaining about.
So. Is it a setting issue, a driver issue, or is it a problem with the hardware? I can't tell you. But what I can say is that when there's any significant metal obstruction between the phone and the sky, the GPS is hit and miss... mostly miss.
I am quite annoyed because whenever I run with my Note the tracking is average to bad. Even under clear sky on a 400m track with no tall buildings around I keep getting errors - most annoying is speed variation.
E.g. today I did 14 tracks (5.6km) at about 5-5.30 mins/lap with 1-2 minute break in total. My speed was constant and average speed is correct but GPS shows high variations.
Is there any way to improve accuracy so I can adjust my speed when necessary? Below is a screenshot from Google Earth after importing my track. I always ran on the first lane. Not across the grass, jumping fences or changing lanes All 14 laps on the first (smallest, 400m lane) which you can see has a white visible contour.
Under your settings-location do you have sensor aiding checked? I think it's generally better not to. You could also try using a different app for tracking the workout. Different apps can poll the gps at different intervals. Finally, not that it's helpful, but my guess would be that running around a track is probably the hardest test for gps because you're constantly changing direction. Have you had better luck with other devices?
mihaig said:
I am quite annoyed because whenever I run with my Note the tracking is average to bad. Even under clear sky on a 400m track with no tall buildings around I keep getting errors - most annoying is speed variation.
E.g. today I did 14 tracks (5.6km) at about 5-5.30 mins/lap with 1-2 minute break in total. My speed was constant and average speed is correct but GPS shows high variations.
Is there any way to improve accuracy so I can adjust my speed when necessary? Below is a screenshot from Google Earth after importing my track. I always ran on the first lane. Not across the grass, jumping fences or changing lanes All 14 laps on the first (smallest, 400m lane) which you can see has a white visible contour.
Click to expand...
Click to collapse
If you are rooted
get 'Faster Fix' from market
select your region from dropdown and - Go
it requires one time only
pezx44 said:
Under your settings-location do you have sensor aiding checked? I think it's generally better not to. You could also try using a different app for tracking the workout. Different apps can poll the gps at different intervals. Finally, not that it's helpful, but my guess would be that running around a track is probably the hardest test for gps because you're constantly changing direction. Have you had better luck with other devices?
Click to expand...
Click to collapse
Yes, I have that option checked because it is supposed to improve accuracy. I will disable and see if that helps.
I use Endomondo and Cardio Trainer and both have the same issue at the highest frequency of gps polling - 1 sec. It's not an app fault because I downloaded the points into GEarth and you can see this is the date they get. I agree they could use better filtering but this is another topic.
It has one of the best GPS chips in existence with GLONASS and a Barometer. Don't think you can make it "better." It's as good as a phone GPS gets.
ericshmerick said:
It has one of the best GPS chips in existence with GLONASS and a Barometer. Don't think you can make it "better." It's as good as a phone GPS gets.
Click to expand...
Click to collapse
I agree to that brother....
For a small built in GPS reciever it works quite well.....
Sent from my GT-N7000 using XDA App
I think, from experience with other phones, that the other sensors will smooth things by assuming you're still moving in a certain direction and can mess things up when turning (which is pretty much your entire run). I personally have never had luck with any sort of gps on a track. I just don't think anything outside of military gps has accuracy fine enough to handle it. If you find otherwise, I'd love to hear about it though.