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You are here: MacNN Forums > Hardware - Troubleshooting and Discussion > iPhone, iPad & iPod > iPhone GPS reception quality in car?

iPhone GPS reception quality in car?
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Mac Elite
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Aug 26, 2008, 02:54 PM
 
Hi! I'm considering purchasing an iPhone by the end of the month, but I was wondering if its GPS function worked well in a car? I remember reading that most GPS didn't work well in cars because of the Faraday cage effect caused by the metal frame or the thick glass. I was planning to build a CarPC a few years ago and most people suggested to use an external antenna.

As the main reason I'm buying an iPhone is the GPS/Google Maps/Web integration (I do road trips a lot), I want to make sure it will work as intended.

Any experience? Thank you!
     
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Aug 26, 2008, 03:09 PM
 
Video iPhone 3G GPS in action.

Personally, I don't use the iPhone in the car much, as I already have a dedicated GPS. However, the few times I have used the iPhone in the car, it's been fine (as has my dedicated Garmin GPS).
     
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Aug 26, 2008, 03:29 PM
 
Works just fine in the car.

But you do know that there is no realtime turn-by-turn directions available.

-t
     
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Aug 26, 2008, 04:45 PM
 
Thank you!

Yes I'm aware of the turn-by-turn limitation. However, this if fine with me as I wouldn't use that feature anyway. I just want to know where I am and to be able to find places like gas stations near me. I might also be tempted to try geocaching.
     
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Aug 26, 2008, 04:48 PM
 
Working fine for me so far.

More than the turn-by-turn directions I miss not being able to set the zoom setting when you're in directions mode. Whenever you tell it to go to the next step it zooms in on the next crossing rather than retaining the current zoom setting. It seems to zoom in pretty close regardless of your speed.
     
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Aug 26, 2008, 08:09 PM
 
Just for you, I tried it yet again inside my car. Quick to lock, and worked for the most part, but it had me travelling beside the road at times, not on it. This is me, driving down Parliament St.



This doesn't usually happen with my dedicated GPS. And even if it does, it usually corrects immediately, but with the iPhone it stayed like that for a few blocks. Not a huge deal, but just FYI. OTOH, it often locks on more quickly than my dedicated GPS at first lock, presumably because of the fact that the iPhone is assisted-GPS whereas my dedicated one is not.

You'll also note that the directions don't correct when you don't follow them. With my dedicated GPS, if you take a wrong turn, it automatically changes the route to compensate. This is just as important as the audible turn-by-turn announcements (and street name announcements on my unit) for dedicated GPSes.
( Last edited by Eug; Aug 26, 2008 at 08:15 PM. )
     
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Aug 26, 2008, 11:00 PM
 
Excellent! Thank you everyone!
     
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Aug 26, 2008, 11:16 PM
 
And for the rest of us..... Yes, it works perfectly fine on the bus, too.
     
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Aug 27, 2008, 01:25 AM
 
If you are in a parking garage, it has some trouble getting a lock but is fine one you're in the open. if moving, it can take a few second to re-acquire but does really well.

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Aug 27, 2008, 04:17 AM
 
Originally Posted by Eug View Post
...but it had me travelling beside the road at times, not on it. This is me, driving down Parliament St.
...
This doesn't usually happen with my dedicated GPS. And even if it does, it usually corrects immediately, but with the iPhone it stayed like that for a few blocks. Not a huge deal, but just FYI.
Judging by that huge blue circle around your dot it did that simply because it wasn't getting a very accurate signal. I've noticed that this easily happens in cities with tall buildings on both sides of the street. With my old Garmin GPS I would see the same behavior. As the buildings get higher and the streets narrower the GPS receiver starts losing satellites and accordingly accuracy goes down.
     
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Aug 27, 2008, 08:44 AM
 
Keep in mind that the iPhone GPS is useless when out of cell range. I ws in Northern Ontario recently and all I could see was a blue dot on an empty screen. Dedicated GPS systems contain the map information locally, whereas the iPhone grabs it as it needs it.
     
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Aug 27, 2008, 09:35 AM
 
Originally Posted by Mastrap View Post
Keep in mind that the iPhone GPS is useless when out of cell range. I ws in Northern Ontario recently and all I could see was a blue dot on an empty screen. Dedicated GPS systems contain the map information locally, whereas the iPhone grabs it as it needs it.
That is true.

However, in the past I have been able to load map areas while still within coverage and then have the blue dot displayed on the previously loaded and cached map data even when out of coverage.
     
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Aug 27, 2008, 09:47 AM
 
Originally Posted by Simon View Post
Judging by that huge blue circle around your dot it did that simply because it wasn't getting a very accurate signal.
Probably.

Originally Posted by Simon
I've noticed that this easily happens in cities with tall buildings on both sides of the street. With my old Garmin GPS I would see the same behavior. As the buildings get higher and the streets narrower the GPS receiver starts losing satellites and accordingly accuracy goes down.
With my Garmin 350 I basically don't see this behaviour. Or if it happens, it corrects itself immediately. The only time I'm off road with the Garmin is when the road isn't on the map, or I'm truly off road.

Parliament St. in that area has low to mid-rise buildings, and the road is fairly wide. (4 lanes IIRC.) Also, I wonder if it's partially because Garmin's software snaps-to-grid. It expects me to be on the road and so if it senses I'm really close to it with a less-than-stellar signal, then perhaps it just maps me on it.

However, I think the Garmin may just track a bit better. I would assume it would, because it's probably a higher power transmitter, and it has a great big antenna that flips up. Plus, the Garmin is usually on the windshield. The iPhone would be sitting on the passenger seat next to me so it's going through the metal roof instead of the glass.

     
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Aug 27, 2008, 09:52 AM
 
That's why I'm thinking about getting some kind of car dock for my iPhone. I want it right up there under the windshield. That way I can see it better and it will probably get better GPS reception. Having it on the passenger seat or on my lap sucks.
     
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Aug 27, 2008, 10:31 AM
 
Originally Posted by Mastrap
Keep in mind that the iPhone GPS is useless when out of cell range. I ws in Northern Ontario recently and all I could see was a blue dot on an empty screen. Dedicated GPS systems contain the map information locally, whereas the iPhone grabs it as it needs it.
D'oh! While I don't think it will happen to me (I don't recall being out of range at any point), that's a serious dealbreaker if you planned to use it as a real GPS. Come on Apple, why offer 95% of the functionality...

Originally Posted by Simon View Post
That's why I'm thinking about getting some kind of car dock for my iPhone. I want it right up there under the windshield. That way I can see it better and it will probably get better GPS reception. Having it on the passenger seat or on my lap sucks.
Does that exist? I'd like one that can rotate easily from portrait to landscape (or can you use it entirely in landscape mode? I don't think so).
     
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Aug 27, 2008, 11:56 AM
 
Kensington has a very nice and sturdy iPhone mount that is unobtrusive when not attached, holds it up quite well and cushions the iPhone nicely in the cradle.

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Aug 27, 2008, 12:20 PM
 
FWIW, my Garmin seems to work fine in the passenger seat. However, it often doesn't work at all when I'm sitting in my office (which is inside a big brick building.).

The iPhone actually can work when I'm sitting in that office. Initially it will give me a very broad location, covering many, many city blocks or even probably several sq. km. (I assume that is based on the cell signal.) But after a certain period it may actually localize me to the right spot (more or less). Assisted GPS is a huge benefit.
     
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Aug 27, 2008, 12:26 PM
 
Originally Posted by FireWire View Post
D'oh! While I don't think it will happen to me (I don't recall being out of range at any point), that's a serious dealbreaker if you planned to use it as a real GPS. Come on Apple, why offer 95% of the functionality...
Amount of data. Our in-car GPS comes with several GB of data on a DVD. Road data for North America alone would probably weigh in at 6-7GB.

My car GPS does snap to grid, for sure. You can see when it locks on and finds the road.
     
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Aug 27, 2008, 12:52 PM
 
Bottom line, for serious GPS applications, the iPhone is NOT a good solution.

It can basically tell you where you are, and then provide static directions a la Google Maps.
No user interaction with the routes and no dynamic re-routing possible.

-t
     
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Aug 27, 2008, 01:17 PM
 
Originally Posted by Mastrap View Post
Amount of data. Our in-car GPS comes with several GB of data on a DVD. Road data for North America alone would probably weigh in at 6-7GB.
The Garmin North America updater disc is significantly smaller. 1 GB maybe? I can't remember off hand, but it's definitely not 6-7 GB, and that's for all of North America including rural areas.

However, that's probably a compressed format. Perhaps your maps are not compressed, or include extra data?
     
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Aug 27, 2008, 01:39 PM
 
Originally Posted by turtle777 View Post
Bottom line, for serious GPS applications, the iPhone is NOT a good solution.

It can basically tell you where you are, and then provide static directions a la Google Maps.
No user interaction with the routes and no dynamic re-routing possible.
Until the TomTom and/or Garmin apps come out, possibly as early as 2.1.

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Aug 28, 2008, 01:30 AM
 
Good evening, as a space systems operator for the AF, and since I have plenty of experience with telemetry, tracking, and control of space assets, the problem with GPS accuracy is not the space vehicle itself or signal strength (4W, 2W for older generations) it produces which govern the accuracy. It is the on ground receiver. All GPS is, is a big orbiting clock and nothing more. Position is calculated on the simple formula d=rt and simple triangulation geometry within the constellation to the ground receiver which is performed by the receiver, then telling you where Starbuck's is. The better the receiver, the better the accuracy.

Thousands upon thousands of variables play a huge part in the calculation of your position. The more the receiver compensates and includes those variables, the better. The biggest problem is signal curvature and reflection off of things in the environment. The buildings, the car, even your body play a part. Distance is calculated simply through ranging from the on ground receiver to the satellite (d), in a straight line to start. The other variables, the buildings for instance, distort that signal. The device thinks the signal comes straight, but it probably bounced off of the building, then the building across the street, down to the street, then finally hits your device. See the problem? So to try to help out the device, you being inside Starbuck's trying to get an accurate position, good luck. Place the device on your dash so it has more view of the sky, don't block it with your body when your out walking by holding it at waist level covering the signal with your head by looking down at it, things like that. The more view of the open sky your device (iPhone) has, the better, which at this point in time come nowhere close to an entry level Garmin or TomTom.
     
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Aug 30, 2008, 07:23 AM
 
I'd only expect fair to good GPS performance from an iPhone versus a Garmin, TomTom, etc. dedicated GPS. The Garmins, for example, have gone through several generations of GPS receive chips and the latest use "high sensitivity" GPS chipsets and can lock on weaker signals in areas where satellite reception is difficult such as downtown areas in cities with a lot of buildings. For example if Apple manages costs by using (only) a 2 megapixel camera I would expect them to do the same by using a mid-grade GPS chipset. My iPhone GPS works well but its positioning is not as consistently accurate as the GPS on my dash...
     
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Aug 30, 2008, 11:33 AM
 
Does anyone know what GPS chip is used in the iPhone 3G ?

According to this rumor, it's not SIRF, but "Global Locate which was recently acquired by Broadcom."

http://seekingalpha.com/article/4774...ps-partnership

Can anyone confirm ?

-t
     
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Aug 30, 2008, 01:16 PM
 
Originally Posted by Eug View Post
Video iPhone 3G GPS in action.

Personally, I don't use the iPhone in the car much, as I already have a dedicated GPS. However, the few times I have used the iPhone in the car, it's been fine (as has my dedicated Garmin GPS).
I used it couple of times but every time I had to go back to my TomTom. Not as good as that.
     
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Sep 1, 2008, 09:37 PM
 
It seems the search feature needs some work. I tried searching the Toronto Zoo. Great, it found it, and provided the address. However, when it actually tries to use that address for directions it claims it doesn't exist.







     
   
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