Google’s specification for an “official” Android unit, that allow it to use Google’s logo and have access to the Android Market, includes a requirement for a built-in GPS receiver. That’s why the new line of Archos Android tablets need their own app marketplace – they don’t come with GPS receivers. So if Android phones come with GPS, why bother with an external Bluetooth GPS receiver, especially when it will cost you extra? Here are a few good reasons:

1. External Bluetooth GPS sidesteps the Motorola “GPS In Airplane Mode” problem.

Posted about this yesterday; basically, some Motorola Android phones have a bug where GPS won’t work if you turn Airplane Mode on. Bluetooth GPS doesn’t have any problems – works perfectly in Airplane Mode.

2. External Bluetooth GPS offers a second position data source, letting you run multiple GPS apps simultaneously.

I’ve noticed that if you have one app getting position data from the GPS, and then start up another app that also looks for GPS data, they don’t always play well together – the second app can take over the GPS data stream completely. If one app supports Bluetooth GPS natively, then you can track position with that, and also run a second app that uses the unit’s internal GPS.

3. External Bluetooth GPS can give you slightly more accurate positions.

I have yet to find a single Android unit that has a GPS chipset that supports WAAS (Wide Area Augmentation Service). WAAS is a satellite signal that broadcasts real-time correction data for several sources of GPS position error, including satellite time/position errors and signal transmission errors in the ionosphere. Not terribly important while the sun is quiet, as it is now, but as the sun moves into a more active phase over the next few years, WAAS can improve the position accuracy by a few meters. Most external Bluetooth GPS receivers come with WAAS turned on as the default.

External GPS units can also come with larger antennas, and have room for bigger (and better) GPS chipsets, allowing for more accurate position determination. And because they’re not tied to your phone, you can place them in a location where they might get better satellite reception, e.g. the top of your backpack, the dashboard of your car, even under your hat. I hope to have a post in the near future comparing the accuracy of my Droid X’s built-in GPS unit, an external Bluetooth GPS receiver, and a high-quality handheld dedicated GPS unit (Garmin 60Cx).

4. Using an external Bluetooth GPS position instead of the built-in GPS can extend the battery life of your Android unit.

In a previous post, I looked at the battery drain from GPS, Bluetooth, WiFi, and cellular. The built-in GPS had the biggest power requirements by far; in comparison, turning Bluetooth on had virtually no effect on battery life. I just ran some additional comparison tests on battery life for the Droid X using internal GPS with Bluetooth off  vs. external Bluetooth GPS. The unit was in Airplane mode in both cases, to eliminate cellular/WiFi power drain. I used the TrekBuddy map app, which lets you choose between the internal GPS and an external Bluetooth GPS as the GPS position source. Approximate battery life is given in hours, based on the time to drop from 100% battery to 60% battery. For one set of tests, the display was turned off; for the second, the display was left on continuously at 50% brightness.

Display offDisplay on (50% brightness)
Bluetooth GPS20.2 hrs9.1 hrs
Internal GPS11.0 hrs5.7 hrs

Results are pretty dramatic – switching from the internal GPS to an external Bluetooth GPS cuts almost doubles battery life when the display is off. Even with the display on, the battery life with the external Bluetooth GPS is actually comparable to some stand-alone GPS units. For example, battery life for the Magellan Triton or deLorme PN-40 units with two AA batteries is often a bit less than 10 hours under normal use. If you remember to turn off the display when you don’t need it, you could easily get 15+ hours of continuous use by switching over to an external Bluetooth GPS.

5. An external Bluetooth GPS is cheaper than a spare battery.

External Bluetooth GPS units aren’t free, but they don’t have to be terribly expensive. Basic models like my Holux M-1000 (which works great with my Droid X), or the Globalsat BT-359 run less than $45, which is the cost of a standard OEM spare battery for my Droid X. My Holux will run for 16 hours on a charge, which is just about the same time you can run the Android phone before it needs recharging as well.

Some Android GPS apps like TrekBuddy already come with built-in native Bluetooth GPS support, which doesn’t require any additional apps or settings. Other apps, like Topo Maps, don’t have native Bluetooth support,  but there are “helper” service apps, free and paid,  that will let those apps use positions from an external Bluetooth GPS as well. I’ll be reviewing some of those in upcoming posts.

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