So let me ask a followup question, or poll maybe. Assuming my GPS is fine, which it seems to be now, why is Find My iPhone always off? I mean if I can see my location on a map, and be off MAYBE 100 yards, why won't Find my iPhone get that precise? I assume it is using the actual lat/lon of the GPS, right? Or maybe it's not? I just figured if the folling logic. If my phone can put a blue dot on the map app, and be pretty dead on, then wouldn't the Find My iPhone use that same info and put the blue dot in the exact same place as shows on the phone? That only makes sense to me.
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Does iPhone have GPS or not???
- Thread starter vbmike73
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Not all apps require high quality location data. Since a GPS lock can cost more in terms of battery, most apps tell the OS that an approximate Cell Triangulation is sufficient. This is most common in apps that run in the background.
Yeah, I can understand that. But what information do you think the iPhone is passing back to MobileMe for Find My iPhone? Wouldn't you think it would pass the truest GPS lat/lon it could obtain?
You apparently are not familiar with the Compass APP:
![20090626compass1.jpg]()
Lat and Lon can be displayed at the bottom.
Just because the app is called compass, doesn't mean that it's getting Lat and Lon from the compass...
A compass tells you your heading in relation to the magnetic poles. It doesn't have any idea where you are on the surface of the Earth.
I'm guessing that there are some issues with either the skyhook database (for wifi locations) or cell tower triangulation (incorrect tower locations) that is causing the initial location to be incorrect. If that were the case, then the GPS lock could end up taking longer than the app is willing to wait. For example, MobileMe might ask for a location, but time out after 30 seconds. Since the initial location was so far off, it would take longer than 30 seconds to get an accurate GPS position.
Again, this is just a guess. I don't have any proof or data to back it up other than a few observations that I've made with my various iPhones.
Just because the app is called compass, doesn't mean that it's getting Lat and Lon from the compass...
A compass tells you your heading in relation to the magnetic poles. It doesn't have any idea where you are on the surface of the Earth.
I'm guessing that there are some issues with either the skyhook database (for wifi locations) or cell tower triangulation (incorrect tower locations) that is causing the initial location to be incorrect. If that were the case, then the GPS lock could end up taking longer than the app is willing to wait. For example, MobileMe might ask for a location, but time out after 30 seconds. Since the initial location was so far off, it would take longer than 30 seconds to get an accurate GPS position.
Again, this is just a guess. I don't have any proof or data to back it up other than a few observations that I've made with my various iPhones.
Definitely seems logical. I'll keep playing with it some more.
Runt888 is probably right, and I wouldn't be surprised if the timeout is even less then 30 secs. The GPS is one of the more power hungry functions on your phone, yet most of the time it is unable to obtain a lock because it's indoors.
BTW- are you testing indoors?
Jesus after this antenna issue people are calling out the iPhone for everything.
Of course it has GPS. In fact, it's GPS is superior to previous models.
Of course it has GPS. In fact, it's GPS is superior to previous models.
Don't be an ass. The 2G did not have GPS and Google Maps location worked just fine, albeit not as precise.
You should read the thread. I've seen the threads you are talking about, but there hasn't been much ranting here. OP had a genuine question relating to why iOS4 location services returns wild variances in accuracy as well as general confusion over the terms A-GPS and GPS.
I'll admit, I was guilty of being indoors. But it's a single level building and I'm 4 ft from a huge window with clear view of the sky. Though there could be a lot of interference in here, too. Once I stepped outside, the GPS kicked in and found my location. But as soon as I stepped back inside, lost the signal apparently, my location went back to being 3+ miles off. Guess that database has the location of my wifi signal incorrect? Is that right?
And I just left my phone outside of the building with GPS lock, and did Find My iPhone, and it gave the same blue dot as appeard on my phone. So I guess everytime in the past that I have tried to find my iPhone and it's been off, I've never had a good GPS lock. That makes perfect sense now.
Thanks for all the help. It's really turned into a popular thread. Although it had nothing to do with the faults of the iPhone 4 (but am pretty happy with my 3GS now). Thanks to everyone who took the time to read this and see it as a legitimate question.
Just because the app is called compass, doesn't mean that it's getting Lat and Lon from the compass...
A compass tells you your heading in relation to the magnetic poles. It doesn't have any idea where you are on the surface of the Earth.
My comment was to the poster who said you can't get lat and lon from A compass...but we were not talking about just A compass, but the Compass App which displays lat and lon values on the bottom, derived from GPS.
Of course you can't get lat and lon from a compass. GEEZ.
For a good lock, you'd need to see four satellites out that window. The satellites are constantly moving (orbit twice a day) and don't go above 55 degrees lattitude.
Being off by that far, means that Skyhook doesn't have your WiFi hotspot mapped, and is only using the connected cell id method.
Btw, there is a lot of confusion about A-GPS. It was caused by Jobs (who is a salesman, not an engineer) misspeaking long ago.
First, what it is NOT. It is NOT cell tower triangulation. It is NOT WiFi triangulation. Those are alternative location methods used when GPS does not work.
For the iPhone, A-GPS simply means that when it does a GPS cold start (not having used it for several hours) it will go ask an Assistance Server on the internet for satellite status and orbit information. This allows it to find the necessary satellites almost instantly.
Without Assistance, it has to search all satellites and download the orbit information from the satellites themselves at 50 bps. That's fifty bits per second. The entire ephemeris takes over twelve minutes to receive.
In the old days, carriers were the only ones with Assistance servers and they were only accessible via carrier control signals. That's why Verizon only allowed their own apps for a long time.
These days, GPS chipmakers run their own Assistance Servers located on the internet. (Although I believe Apple uses their own cache servers, which simply keep an updated copy of the chipmaker's server data. This allows Apple more control.)
GPS - Assisted GPS
I don't normally add posts to these things, they are very useful when people post positive advice. I don't get the people who have so much spar time on their hands to make sarcastic comments! This is about clarifying GPS - AGPS not a discussion about communism and capitalism!
Anyway. I believe the confusion was caused by the phone makers including Apple. As a sailor I have known GPS as the term Global Positioning System (yes we all know that already) for many years before it was applied to mobile phones and only satellite based (an American military system initially, I'm sure you knew that too). The manufacturers used Assisted GPS as a term when using triangulation from radio masts only. It is of course a form of global positioning system but you can not globally position yourself with AGPS!! only if you exist solely in the zone of mobile phone signals. There is still a lot of world out there that isn't.
To the people who never leave a cellnet zone and really don't get the satellite and great blue yonder out there beyond the freeways and bypasses...maybe you just need to get a life.
No thanks to Noah82, totally getting it the wrong way round -Aggie- but many thanks to Mmoto.
I don't normally add posts to these things, they are very useful when people post positive advice. I don't get the people who have so much spar time on their hands to make sarcastic comments! This is about clarifying GPS - AGPS not a discussion about communism and capitalism!
Anyway. I believe the confusion was caused by the phone makers including Apple. As a sailor I have known GPS as the term Global Positioning System (yes we all know that already) for many years before it was applied to mobile phones and only satellite based (an American military system initially, I'm sure you knew that too). The manufacturers used Assisted GPS as a term when using triangulation from radio masts only. It is of course a form of global positioning system but you can not globally position yourself with AGPS!! only if you exist solely in the zone of mobile phone signals. There is still a lot of world out there that isn't.
To the people who never leave a cellnet zone and really don't get the satellite and great blue yonder out there beyond the freeways and bypasses...maybe you just need to get a life.
No thanks to Noah82, totally getting it the wrong way round -Aggie- but many thanks to Mmoto.
Wrong and this has been covered in many threads since 2010.
aGPS is GPS. That's why GPS is part of the acronym. The only difference between aGPS and standalone GPS is that aGPS can utilize assistance servers for a faster initial fix. That's it. It still uses the GPS satellites to determine location. Many aGPS receivers can fall back on standalone mode if the assistance servers are not available.
aGPS is not tower triangulation. For some reason that's a common misconception.
The iPhone has true GPS. It does not require cel tower or Wifi location; it can find itself completely on its own.
The only caveat is that without cel towers or Wifi information, it may take a long time to get a GPS fix. This is standard behavior for GPS receivers.
Sometimes when on a flight I use GPS to show my current speed and location. (The SIM card is locked out so the cel radio remains shut down). It takes up to a couple minutes to get a lock, but when I do, it shows me traveling at 500+ MPH at 30K+ feet, with my location on the map, just as it should, with no cel towers or Wifi at all. Just satellites.
The only caveat is that without cel towers or Wifi information, it may take a long time to get a GPS fix. This is standard behavior for GPS receivers.
Sometimes when on a flight I use GPS to show my current speed and location. (The SIM card is locked out so the cel radio remains shut down). It takes up to a couple minutes to get a lock, but when I do, it shows me traveling at 500+ MPH at 30K+ feet, with my location on the map, just as it should, with no cel towers or Wifi at all. Just satellites.
To all the people who don't know the answer to this question because you never leave cell service; I feel sorry for you.