Are there any GPS dock\chargers\windshield mounts for iPhone 4 yet?

I've used the tomtom car kit with an iphone 3g for a year and a half, and the gps reception was much better with the car kit, making car navigation really quite functional; driving through a skyscraper canyon in a major city it gets iffy, but otherwise, it's been pretty good. Just upgraded to the iphone 4, and for the record, it has worked fine for me with the TomTom car kit so far. There's some debate about whether the car kit gps receiver/antenna or the iphone 4s' gps receiver is more accurate; the consensus is that they're close, in any case. (I think one of the major factors in the accuracy of gps reception is antenna size and design, and the iphone 4's use of the metal band as an antenna might have something to do with its improved gps accuracy.)

So, if I didn't already own the TomTom car kit, I'd be looking at alternatives like the Kensington 2-in-1 Car Charger and AUX Audio Cable coupled with perhaps a Proclip passive mount, which would give a solid mount plus charging plus aux-out to play things through my car stereo. Wouldn't have the TomTom's speakerphone, but some may not be interested in that part anyway.
 
WOW ... BIG EDIT\RETRACTION HERE...

So I initially posted asking for a dock charger because I was under the impression that there was no "real GPS" in the iPhone 4. Using the external dock would solve the issue, but I opened a complaint case with Apple as they claim there is real gps...

Today, one of their iPhone engineers called me back to discuss... and confirmed the design of the GPS as was pointed out but unconfirmed by others:

When you hold the phone (iPhone 4) in your hand and activate a location app, it uses triangulation to get an initial fix on your location within a 3 mile radius, which we all knew. This takes 1-5 seconds. It then tries to improve the reliability by using 3 towers, usually giving a 300 yard radius, usually taking 5-20 seconds.

Where the iPhone keeps going is IF there's a CAR or WALL CHARGER plugged in, it activated the real GPS receiver inside, and looks for satellites, and generally will get a fix within 20 seconds. It was designed this way because the GPS receiver takes significant power, so they've designed it to work with a car charger or home charger's power.

I did a few tests and found this is absolutely the case. I use a windshield mount (just a generic holder with a special iPhone 4 clip. When I turn the phone off, turn it on, open GPS app, it finds my position within a couple blocks. As soon as I plug in the car charger, it narrows down the reliability to what I'd guess is about 10 feet. WOW....

Sorry for the misinformation going back and forth. With 3GS it required an external GPS dock for true GPS, but it looks like Apple fixed this and added real GPS on 4.. yay!
 
bella92108 said:
WOW ... BIG EDIT\RETRACTION HERE...

So I initially posted asking for a dock charger because I was under the impression that there was no "real GPS" in the iPhone 4. Using the external dock would solve the issue, but I opened a complaint case with Apple as they claim there is real gps...

Today, one of their iPhone engineers called me back to discuss... and confirmed the design of the GPS as was pointed out but unconfirmed by others:

When you hold the phone (iPhone 4) in your hand and activate a location app, it uses triangulation to get an initial fix on your location within a 3 mile radius, which we all knew. This takes 1-5 seconds. It then tries to improve the reliability by using 3 towers, usually giving a 300 yard radius, usually taking 5-20 seconds.

Where the iPhone keeps going is IF there's a CAR or WALL CHARGER plugged in, it activated the real GPS receiver inside, and looks for satellites, and generally will get a fix within 20 seconds. It was designed this way because the GPS receiver takes significant power, so they've designed it to work with a car charger or home charger's power.

I did a few tests and found this is absolutely the case. I use a windshield mount (just a generic holder with a special iPhone 4 clip. When I turn the phone off, turn it on, open GPS app, it finds my position within a couple blocks. As soon as I plug in the car charger, it narrows down the reliability to what I'd guess is about 10 feet. WOW....

Sorry for the misinformation going back and forth. With 3GS it required an external GPS dock for true GPS, but it looks like Apple fixed this and added real GPS on 4.. yay!
Click to expand...

Tried to tell ya. But respect to you for the edit/retraction, not many people have the honesty or balls to come back and admit they were wrong, especially after a heated discussion. So big respect to you for that.

However, you still have got it a bit wrong. The "real GPS" still works when not connected to a dock or power source. I hike a lot (was out on monday) and it works great. MotionX GPS app reported accuracy to within 16 feet, and it was about right. I had no cell network coverage, but even if i did triangulation does not get even close to that accuracy, especially in the mountains where triangulation does not work well.

But yes, location services does work in a low power mode when not externally powered. Many GPS apps can still run in a higher power mode though, which of course hammer battery life.

The 3GS is no different, but the iPhone 4 does have a slightly updated and tweaked GPS chipset which performs a bit better. A quick googles tells me the iPhone 4 uses the Broadcom's BCM4750 GPS chip and the 3GS used Infineon's PMB2525 (Hammerhead II).

The Broadcom chipset offers up to -157 dbm assisted acquisition and -162 dbm tracking sensitivity, outnumbering the SiRF III chipset with -155 dbm resp. -159 dbm.
Click to expand...

Which is interesting because the SiRF III used to be one of the most common GPS Chip's and was used in many TomTom's and Garmins etc. My old TomTom One and the Holux BT unit i used with my WinMob used the SiRF.

There is no fundamental difference between the iPhone GPS chip type and the chips found in standalone TomTom's etc, other than they have the extra benefit of Assisted location data to help lock onto the sats quicker. But the chip in standalone car sat navs tend to be a bit more powerful and have more channels - they know they will always have a power source and can max out.
 
domrevans said:
Tried to tell ya. But respect to you for the edit/retraction, not many people have the honesty or ball to come back and admit they were wrong, especially after a heated discussion. So big respect to you for that.

However, you still have got it a bit wrong. The "real GPS" still works when not connected to a dock or power source. I hike a lot (was out on monday) and it works great. MotionX GPS app reported accuracy to within 16 feet, and it was about right. I had no cell network coverage, but even if i did triangulation does not get even close to that accuracy, especially in the mountains where triangulation does not work well.

But yes, location services does work in a low power mode when not externally powered. Many GPS apps can still run in a higher power mode though, which of course hammer battery life.

The 3GS is no different, but the iPhone 4 does have a slightly updated and tweaked GPS chipset which performs a bit better. A quick googles tells me the iPhone 4 uses the Broadcom's BCM4750 GPS chip and the 3GS used Infineon's PMB2525 (Hammerhead II).

There is no fundamental difference between the iPhone GPS chip type and the chips found in standalone TomTom's etc, other than they have the extra benefit of Assisted location data to help lock onto the sats quicker. But the chip in standalone car sat navs tend to be a bit more powerful and have more channels.
Click to expand...

Thanks. Maybe the app can force full GPS? I would LOVE to know how to make Navigon force the GPS on. I'm only using it for car navigation, and between TomTom (1.6) and Navigon (1.5), I prefer Navigon because it adds terrain, which is friggin cool when driving through the hills and valleys of San Francisco. I'd like to not have to plug it in everytime I get in the car. Do you think it's a limitation placed on Navigon and TomTom? I haven't t tried MotionX...

Also, my iPhone is the UK Factory unlocked model, would that be any different you think?
 
more on iphone 4 car kit options

I got a new case for my iphone 4 which doesn't fit in the TomTom car kit (and which is a pain to take on and off), so I had one of these generic mounts, and ordered this split audio/power cable, which together allow my iphone 4 to be on my dash while simultaneously plugged into both power and my car's aux port, for a total cost of around $20. Conclusions: 1) the iphone 4's gps is noticeably better than the tomtom car kit's gps, so if you have an iphone 4, you don't need the tomtom car kit's boosted gps reception. 2) The TomTom car kit is very elegant, allows one-handed easy iphone insertion and removal, and rotates easily but firmly from portrait to landscape mode, which is nice. My current cheapo setup doesn't do that nearly as well, because you have to plug the phone into the cable with two hands, and it doesn't rotate conveniently or securely. 3) I have a small car which is loud on the freeway; I find I don't miss the TomTom car kit's speaker because when I'm driving slowly, the iphone's speakerphone is actually adequate, and when I'm on the freeway, I find it necessary to use a noise canceling bluetooth headset anyway.

Caveats: Some folks have reported a buzzing noise when playing music over their car stereo via the cable I bought. GPS reception varies given type of car, placement, and other things, so you might not have the same experience as I.

Conclusion: If someone made a mount as elegant as the TomTom car kit, but case-friendly and without the electronics I no longer need, I'd buy it if it were $20 or less.

tstreete said:
I've used the tomtom car kit with an iphone 3g for a year and a half, and the gps reception was much better with the car kit, making car navigation really quite functional; driving through a skyscraper canyon in a major city it gets iffy, but otherwise, it's been pretty good. Just upgraded to the iphone 4, and for the record, it has worked fine for me with the TomTom car kit so far. There's some debate about whether the car kit gps receiver/antenna or the iphone 4s' gps receiver is more accurate; the consensus is that they're close, in any case. (I think one of the major factors in the accuracy of gps reception is antenna size and design, and the iphone 4's use of the metal band as an antenna might have something to do with its improved gps accuracy.)

So, if I didn't already own the TomTom car kit, I'd be looking at alternatives like the Kensington 2-in-1 Car Charger and AUX Audio Cable coupled with perhaps a Proclip passive mount, which would give a solid mount plus charging plus aux-out to play things through my car stereo. Wouldn't have the TomTom's speakerphone, but some may not be interested in that part anyway.
Click to expand...
 
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bella92108 said:
Thanks. Maybe the app can force full GPS? I would LOVE to know how to make Navigon force the GPS on. I'm only using it for car navigation, and between TomTom (1.6) and Navigon (1.5), I prefer Navigon because it adds terrain, which is friggin cool when driving through the hills and valleys of San Francisco. I'd like to not have to plug it in everytime I get in the car. Do you think it's a limitation placed on Navigon and TomTom? I haven't t tried MotionX...

Also, my iPhone is the UK Factory unlocked model, would that be any different you think?
Click to expand...

A-GPS is 'full' GPS with an aid to get a quick lock by having an early rough location to know which satellites should be in the sky, and where.

The problem is that the 3G/3GS GPS chips/antenna led to fairly inaccurate location readings. It was also quite vulnerable to the usual GPS issues like multipath errors in cities. When I got the iPhone 4, I noticed the gap between a dedicated PND and the iPhone was extremely small. The iPhone 4 handles multipath quite well, and I've only had minor blips on the same scale that the PNDs I've used in the past have given me.

TomTom and Navigon use the same GPS feed that all other apps on the iPhone use, so when MotionX is reporting 16ft accuracy, TomTom sees the same thing.

When I had my 3G/3GS, I definitely felt the need for a car dock of some kind. I got the 4, noticed docking issues with the TomTom car dock, and wound up jury rigging my own cradle in the end just to hold the phone in the right place for navigation and make it easy to run a power cable. I did some comparisons when the 4 came out between the 3GS, 4, and the TomTom dock and felt that with the 4, the dock wasn't needed as the GPS sensitivity was much improved.

I do believe you can relax. :)

EDIT: Wow, didn't realize I necro'd an extremely old thread while searching. Ouch.
 
Last edited:
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