Comments on: Skyhook: how iPhone OS 3.0 delivers location services

By: Senate hearings become Apple witch hunt.

Senate hearings become Apple witch hunt. — Wed, 11 May 2011 13:57:56 +0000

[...] I wrote in July 2009, iPhone (and I’m sure all other mobile handsets today) uses assisted GPS, or AGPS, which is an amalgam of WiFi, cell tower location, and GPS data, to locate the device. It is a [...]

By: Bill Boyd

Bill Boyd — Wed, 13 Jan 2010 13:28:50 +0000

I am using the older Iphone 2G in the Dominican Republic. I had on location services. Half the time I find a wifi hotspot. What I noticed was that all the minutes I had on my phone was eaten up. Beware if you're using your iphone without a data package; especially outside the country. My Iphone is jailbroken so I can constantly change sim chips depending on where I am at.

By: HarryUSA

HarryUSA — Tue, 08 Dec 2009 00:59:49 +0000

I was looking for information on how an iPhone application retrieves the location information and passes it back to the server the app is communicating with. On my iPhone certain apps ask if it is OK to share my location with the application. Does anyone know where more info can be had on this subject?

By: Andrew Robulack

Andrew Robulack — Thu, 05 Nov 2009 08:43:35 +0000

Lol. Just picked up a Bell iPhone 3GS in Whitehorse today and its location services showed me as being in Edmonton. Not quite the accuracy you’re getting! Seems these Skyhook folks have a bit of work to do on the nether regions of the world.

By: Alec

Alec — Sat, 18 Jul 2009 10:28:46 +0000

My understanding, Randall, is that WiFi location is accomplished by mapping MAC address of the access point to known GPS coordinates. You can actually manually submit an access point to their database by visiting this page: http://www.skyhookwireless.com/howitworks/submit_ap.php. I presume that when an access point broadcasts SSID it must also be broadcasting the MAC address of the access point.

And yes, the miss can be huge. With 850 Mhz towers 1km is pretty common, but in rural areas the power can be increased in order to space the towers apart. There’s a tower in downtown Ottawa that I know of where experiments have been run showing that with sufficient power the cellular signal can reach the Camp Fortune ski hill nearly 20km away.

By: Randall Howard

Randall Howard — Fri, 17 Jul 2009 16:07:56 +0000

Alec,
interesting post – IO was wondering how all this location information fit together and the AGPS is cool. I’m still wondering how they get the WiFi information since most of them are private unless it’s somehow using some kind of IP-mapping?

Anyway, your comment about pure cellular tower triangulation where you mention 3000 feet (why still use feet, i’ve almost forgotten what they are) seem low. At my house, in a rural location and probably with 850MHz towers, my fix is about 4.5 km wrong – that’s a huge miss. So, perhaps it just depends on how many towers and how widely they are spaced.

Randall

By: Verizon courts developers too late? | Alec Saunders SquawkBox

Verizon courts developers too late? | Alec Saunders SquawkBox — Tue, 14 Jul 2009 11:23:18 +0000

[...] The location data provided by the carrier is the lowest quality available. See my piece on iPhone location services and SkyHook Wireless for more [...]

By: David Janes’ Code Weblog » How iPhone OS 3.0 delivers location services

Sat, 27 Jun 2009 11:38:46 +0000

[...] Saunders has a seriously cool article on his blog about how your iPhone knows where it is. I got to experience how well this works yesterday when we [...]