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GPS always available?
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The ignorance and misunderstanding on these location services issues is astounding. How can the iPhone be out (in one incarnation or the other) for nearly 3 years and people still not understand how it works? There are articles all over the web (wiki and otherwise) that fully explain it all.
In a nutshell... Modern Apple mobile devices may contain up to THREE types of location services...
WiFi Hotspots via Skyhook Wireless - The folks at Skyhook Wireless drove their specially equipped vehicles all over the US (literally, up and down the majority of the streets) and used the equipment to detect and map the location of millions of WiFi Hotspots. For a mobile device to successfully use WiFi location it needs two things... 1) A WiFi hotspot that has been mapped by Skyhook Wireless. 2) A connection to the internet so the Skyhook Wireless database is accessible. The device only needs ONE WiFi hotspot (that has been mapped by Skyhook) to successfully locate its position. WiFi location by itself doesn't use "Triangulation". It simply detects the WiFi hotspot and places you exactly at the location for that hotspot as stored in the Skyhook Wireless database. This method is extremely accurate because you pretty much have to be right on top of the WiFi hotspot to detect the signal. But, remember, you ALSO have to have ACCESS to that WiFi hotspot (or some other form of internet connection).
Cellular Triangulation - The mobile device must, of course, contain a cellular radio. It then uses the relative signal strength of multiple nearby cellular towers to approximate the mobile device's location. Depending on concentration and distance of cellular towers, this location method can be be fairly inaccurate, placing the device up to several blocks away from its real location.
GPS - Some mobile devices contain a REAL GPS. These devices use the satellite signals for location services. Just like a TomTom or Garmin navigation. This method of location service is highly accurate. Caveat: The accuracy drops dramatically without a clear view of the sky (eg, indoors, etc.).
OK... in addition to each of the individual methods, some devices use combinations of the three. For example... A-GPS or Assisted GPS. The device has a REAL GPS chip but, as anyone know that owns a TomTom or a Garmin, if you turn the GPS off and move it to a different (distant) location before turning it back on, it can sometimes take quite a few minutes before it finds its location again. With A-GPS, the device will also have a cellular radio built in. The device uses Cellular Triangulation to more quickly place the approximate location, which then makes it easer for the GPS (satellites) to pin down the exact location. The Cellular Triangulation ASSISTS the GPS.
Assisted GPS (A-GPS) = A REAL GPS plus help from cellular triangulation.
So that's, basically, how it all works. And here's what each Apple device uses for location services:
• Original iPhone - WiFi via Skyhook Wireless AND Cellular Triangulation. Since the cellular radio gives the original iPhone a constant internet connection (to communicate with Skyhook's database), the original iPhone actually did a pretty good job when there was a mapped WiFi hotspot nearby.
• iPhone 3G - WiFi via Skyhook Wireless, Cellular Triangulation AND GPS. All three working together for very accurate location services.
• iPhone 3GS - WiFi via Skyhook Wireless, Cellular Triangulation AND GPS. All three working together for very accurate location services. (The 3GS also has a digital compass.)
• iPod Touch - WiFi via Skyhook Wireless. That's it! No GPS and no Cellular Triangulation.
• WiFi-only iPad - WiFi via Skyhook Wireless. That's it! No GPS and no Cellular Triangulation. (The WiFi-only iPad also has a digital compass.)
• 3G iPad - WiFi via Skyhook Wireless, Cellular Triangulation AND GPS. All three working together for very accurate location services. (The 3G iPad also has a digital compass.)
As you can see, just like the iPod Touch, the WiFi-only iPad has just WiFi via Skyhook Wireless for location service. See the description for WiFi above again. You need TWO things for an accurate location with WiFi. If the hotspot isn't mapped by Skyhook (the hotspot is too new or the base station was changed since Skyhook mapped the location), or if the WiFi-only iPad doesn't have access to the internet through the WiFi hotspot (or via some other means), then the WiFi-only iPad is out of luck as far as location services is concerned.
If you want an iPad that has the most accurate and reliable location services possible, then your choice MUST be the 3G model.
Mark
In a nutshell... Modern Apple mobile devices may contain up to THREE types of location services...
WiFi Hotspots via Skyhook Wireless - The folks at Skyhook Wireless drove their specially equipped vehicles all over the US (literally, up and down the majority of the streets) and used the equipment to detect and map the location of millions of WiFi Hotspots. For a mobile device to successfully use WiFi location it needs two things... 1) A WiFi hotspot that has been mapped by Skyhook Wireless. 2) A connection to the internet so the Skyhook Wireless database is accessible. The device only needs ONE WiFi hotspot (that has been mapped by Skyhook) to successfully locate its position. WiFi location by itself doesn't use "Triangulation". It simply detects the WiFi hotspot and places you exactly at the location for that hotspot as stored in the Skyhook Wireless database. This method is extremely accurate because you pretty much have to be right on top of the WiFi hotspot to detect the signal. But, remember, you ALSO have to have ACCESS to that WiFi hotspot (or some other form of internet connection).
Cellular Triangulation - The mobile device must, of course, contain a cellular radio. It then uses the relative signal strength of multiple nearby cellular towers to approximate the mobile device's location. Depending on concentration and distance of cellular towers, this location method can be be fairly inaccurate, placing the device up to several blocks away from its real location.
GPS - Some mobile devices contain a REAL GPS. These devices use the satellite signals for location services. Just like a TomTom or Garmin navigation. This method of location service is highly accurate. Caveat: The accuracy drops dramatically without a clear view of the sky (eg, indoors, etc.).
OK... in addition to each of the individual methods, some devices use combinations of the three. For example... A-GPS or Assisted GPS. The device has a REAL GPS chip but, as anyone know that owns a TomTom or a Garmin, if you turn the GPS off and move it to a different (distant) location before turning it back on, it can sometimes take quite a few minutes before it finds its location again. With A-GPS, the device will also have a cellular radio built in. The device uses Cellular Triangulation to more quickly place the approximate location, which then makes it easer for the GPS (satellites) to pin down the exact location. The Cellular Triangulation ASSISTS the GPS.
Assisted GPS (A-GPS) = A REAL GPS plus help from cellular triangulation.
So that's, basically, how it all works. And here's what each Apple device uses for location services:
• Original iPhone - WiFi via Skyhook Wireless AND Cellular Triangulation. Since the cellular radio gives the original iPhone a constant internet connection (to communicate with Skyhook's database), the original iPhone actually did a pretty good job when there was a mapped WiFi hotspot nearby.
• iPhone 3G - WiFi via Skyhook Wireless, Cellular Triangulation AND GPS. All three working together for very accurate location services.
• iPhone 3GS - WiFi via Skyhook Wireless, Cellular Triangulation AND GPS. All three working together for very accurate location services. (The 3GS also has a digital compass.)
• iPod Touch - WiFi via Skyhook Wireless. That's it! No GPS and no Cellular Triangulation.
• WiFi-only iPad - WiFi via Skyhook Wireless. That's it! No GPS and no Cellular Triangulation. (The WiFi-only iPad also has a digital compass.)
• 3G iPad - WiFi via Skyhook Wireless, Cellular Triangulation AND GPS. All three working together for very accurate location services. (The 3G iPad also has a digital compass.)
As you can see, just like the iPod Touch, the WiFi-only iPad has just WiFi via Skyhook Wireless for location service. See the description for WiFi above again. You need TWO things for an accurate location with WiFi. If the hotspot isn't mapped by Skyhook (the hotspot is too new or the base station was changed since Skyhook mapped the location), or if the WiFi-only iPad doesn't have access to the internet through the WiFi hotspot (or via some other means), then the WiFi-only iPad is out of luck as far as location services is concerned.
If you want an iPad that has the most accurate and reliable location services possible, then your choice MUST be the 3G model.
Mark
What someone needs to do next is to come out with a standard so that you can register your home wifi with an address.
I just installed a different version of dd-wrt on my linksys last night, and when I tried my ipad, it thinks I'm in IL instead of CA, heh. At work though, it's very accurate.
I just installed a different version of dd-wrt on my linksys last night, and when I tried my ipad, it thinks I'm in IL instead of CA, heh. At work though, it's very accurate.
You can submit an update via Skyhook's website: http://www.skyhookwireless.com/howitworks/submit_ap.php
You were doing so well up until this. The 3G and 3GS BOTH have GPS chips. Nice job otherwise.
Tried turning WHAT off? If you're talking about the WiFi iPad, it DOESN'T HAVE A GPS CHIP.
Thank you! Corrected. I shouldn't type these things so late at night. (I also added which models come with a digital compass.)
Mark
I wonder if we'll ever be able to determine or not, other than the length in which it takes the GPS to determine position.
I need to set a bookmark to that post for everone who keeps bringing up GPS and the iPad WiFi. The digital compass aspect is good as well. I will be glad to finally have a model with the compass.