Saturday, September 24, 2011

Does Android GPS Need Cell Service to Work?

Google Maps appears to use cell towers to locate a user indoors when the LG Optimus V's GPS can't find a satellite signal. But what if you're out of doors and a satellite signal's all you've got?

To follow up on my last post, Top 5 Virgin Mobile LG Optimus V Annoyances, I’ve uncovered interesting intelligence contradicting my Annoyance #4, GPS System Needs Cell Service to Function.

After searching on Android Market for GPS apps I found one, BackCountry Navigator, that’s designed for hiking in remote places where cell service is typically unavailable. BackCountry Navigator’s developer, Nathan Mellor, blogged last spring about the ability of his app to work far from cell or WiFi signals. He notes:
Android Apps can get a location with the help of cell towers.
If you look at the location settings of an Android phone, you will often see two different kinds of locations mentioned. One is called the network location. This is found using cell towers or wifi hot spots. It is only a rough location.
The other is the GPS satellite location which is what you need for navigation. Android phones, like many smartphones, also use Assisted GPS (aGPS). This allows them to compute satellite position using the network and get the location faster.

The Android GPS can also get a location without cell towers. 
It is common to think that a cell phone can't get a location without cell service. In fact, if you ask the average employee of your cell service provider if you can use the phone's GPS without cell service, they will say no. It is often beyond their comprehension that anyone would want to, plus they want to sell you software that uses an expensive data plan.
An Android phone has a real GPS chip in it, which can get the location from GPS satellites.
But as you’d imagine, his comment that Assisted GPS using cell towers or WiFi hot spots lets smartphones “compute satellite position using the network and get the location faster” means that when cell towers or WiFi hot spots aren’t around pinpointing your location takes a little longer. Mellor goes on to say:
Getting a first location in the backcountry (a first fix) requires patience.
If you've used your Android GPS in urban areas, you may have to adjust to how long it takes to get your location the first time in the backcountry. Instead of ten seconds, it might be 1-5 minutes. It won't have the benefit of aGPS to get the satellite locations faster. Don't worry. The next time you start your GPS, it will probably take less than ten seconds.
So it would seem that’s why any smartphone, android or not, uses aGPS instead of plain GPS: to pinpoint your location in seconds instead of minutes.

Which means Virgin Mobile’s LG Optimus V actually doesn’t need cell service for its GPS system to work.  However, it does need an app, like BackCountry Navigator, that functions happily when cell signals are nowhere to be found.

Unfortunately, that also means an app that doesn’t use android's default Google Maps the way Google Navigation does. Google Maps clearly relies on cell service to locate users quickly and, when none is available, fails to resolve your position on your phone’s display ... as I discovered when I took my LG Optimus V to the wilds of western Maryland.

But BackCountry Navigator, while it doesn’t use Google Maps, is hardly a suitable alternative for car travel.  It's designed to use topographical maps from or the U.S. Geological Survey -- useful for hiking over exotic terrain but hardly useful for driving.  (And since hikers don't need turn-by-turn spoken directions, it seems obvious BackCountry Navigator doesn't deliver those, either.)

I found an alternative, Sygic, whose Android Market product page boasts that its maps "are stored on the phone for offline use." I'd hoped that claim meant it would work without cell service, but, alas, I couldn't get Sygic to run on my Optimus V. And it may not have mattered, because before you can use Sygic you've got to download its maps -- and that turns out to be time-consuming.  For instance, if, like me, you're primarily interested in traveling in North America Sygic asks you to download maps state by state. I limited my selection to Connecticut, Massachusetts, New Jersey, and New York, but together they added up to 749 MB and took me more than 10 minutes to get onto the phone via home WiFi. And, of course, Sygic's à la carte map requirements mean you've got to remember to download additional maps before you can drive through states Sygic doesn't already know about. Pretty cumbersome.

Has anyone landed on a solution to this irksome problem? Is there another app that does what Sygic promises without the onerous map download requirements?

The easiest answer would be for Google to include an option allowing Google Maps to locate users using only their android phone's GPS chip. It occurs to me, though, that Google Maps also needs cell service to stream Google Maps details (some of which may be commercial, such as restaurant, store, or hotel locations) to your phone on the fly, so it can sidestep Sygic's heavy-duty offline map storage requirements.

If that's the case there may never be a solution for Virgin Mobile android phone users -- at least as long as we're using the LG Optimus V's less than perfect radio antenna on Sprint's less than ubiquitous network.

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