Accuracy of iPhone Location?

There is a lot of info posted back when 1.1.3 was released.

First note, when using towers only, it does not triangulate.
It uses data from one tower and from historical info about signal strength of phone to that tower with past data of phones that have recorded GPS locations earlier in that area at the same strength. That is how it decides how big of a circle to draw.

So hitting towers, it really just gets you in the area. Which is perfectly fine for finding stuff around you (but of course not for turn by turn directions). But that is what Drop Pin is for.

For WiFi. It was all mentioned how they do it. You can read more about the company they work with ( http://www.skyhookwireless.com/howitworks/coverage.php ) but in general Skyhook has surveyed most major poupulation areas and mapped out (GPS) WiFi spots. So if you just have WiFi turned on (not need to be connected to a spot) when you hit "Find Me" it will behind the scenes look at all the networks around you (just reads MAC addresses) sends that data to Skyhook looking for matching MAC addresses. If found, then it will use their info as it is much more accurate and then can usuall bring you down to the street corner level. If no match is found, then it will use tower info.

I know where I live I never get a WiFi hit, but at work (Arlington, VA) when out and about, it almost always get WiFi hits and brings me right down to where I am.

So the SDK is just going to let Apps tap into that same way of finding you. Can be uses in Apps like those of a Social Nature maybe. Be able to "find friends last reported location" etc (though no background running processes are allowed so only will be able to do stuff like that when all people have the app open).

Message was edited by: DaVBMan

Google Maps gets its location information from Skyhook Wireless. You can check them out at http://www.skyhookwireless.com
They will map lat/log on cellular towers and WiFi information they get in drive arounds. That gives them information based on what is read in your iPhone for your connection.
Good luck on GPS accuracy down to 5 feet since the iPhone doesn't have a GPS chip. After working for years with wirless carriers in the E911 arena, I know that most of them will not give you better than 10 meters accuracy. It can be better, but that is the best most of them will guarantee.

Hope this helps you.

I would not trust the accuracy of google maps on the iPhone.

I live in New Milford, Connecticut. Saturday as I was heading down my driveway I hit the Locate me button on my iPhone. It showed my location as Anantapur, a city in India. That's about 8,014 miles off.

Any ideas how to narrow it down a little closer?

Mark

Anychance you use to live where it said you were?
Reason I ask, is when they surveyed WiFi spots, the record MAC addresses. Now if a router they found ends up moving to a new location, they still have the old location recorded. So could be that you moved, or maybe your neighbor and you/they are using the router you/they had at old place.

In time Skyhook picks up on the fact that a MAC address is no longer listed around other known MAC addresses thus they self repair their data (remove bad ones) or gets found with new survey.

But when you are way off and know you are way off. Go into Settings, then Wifi, and turn it off. This will force it to use the Cell tower only. It will always choose WiFi over Cell if WiFi is on and it finds a known Mac address.

Nope, never been to India. The furthest I have been from Connecticut with the iPhone is Michigan.

But I do have a neighbor who is from India and travels a lot. Could he have a wireless router that he perhaps purchased in India?

I'm just guessing?

After saying that, and now that the SDK is out I am hoping that one of the GPS software providers will make true GPS for the iPhone. I already have a Blue Tooth GPS receiver I use with my Laptop.

Mark

With Wi-Fi off, my location is off by about 1/4 mile.

With Wi-Fi on, it puts about a 3-house-wide circle centered on the house across the street.

When I go to Settings/WiFi, the only Wi-Fi it can see is my own home Wi-Fi, so presumably that's the one it is picking up.

I had no idea SkyHook knew where I live. That's sort of Big Brotherish. Yet another reason to loose sleep.

Have a paranoid day,

-Peter 😉

Big problem with that though. One of the SDK restrictions is that developers will have zero access to the 30pin connector. Thus an app cannot be made to work with an accessory (which will be needed if you are expecting a 3rd party GPS provider to make something).

Actually, you can use bluetooth for GPS with something like http://www.freedominput.com/site/index.php?Itemid=106&id=96&option=com_content&t ask=view

Why would I need access to the 30 pin connector? I have a Pahros Wireless (Bluetooth) GPS receiver. All I need is Software on the iPhone to talk to the GPS via bluetooth. And actually if I turn on the receiver the iPhone sees it now, and even recognizes it as Pharos.

Mark

You don't need access to the connector if the appropriate bluetooth protocol is available.

Does the iPhone support the Serial Port Profile (SPP) in the SDK?

I don't know. I'm not a developer.

Actually, you can use bluetooth for GPS with something like ...

Actually you can't.

Does the iPhone support the Serial Port Profile (SPP) in the SDK?

No, it doesn't. Which is why you can't use what was suggested above.

I had no idea SkyHook knew where I live. That's sort of Big Brotherish. Yet another reason to lose sleep.

They don't. All they know is where a particular WiFi router is. Or was.

However, when we all downloaded the update with Google Maps locator, we agreed to Google collecting anonymous information about what searches were done from what areas.

Having to work directly with Skyhook is going to present challenges...

They have a free SDK you can download and try out. Good luck! Unfortunately, they haven't surveyed where I live, so the SDK didn't work for me 🙂

How can you say no? You don't work for Apple or Freedom GPS. You don't know what protocols Apple will approve or not approve.