RIM adds BlackBerry geolocation, minus GPS
How do you zero in on a location without using GPS? You use cell phone towers.
BlackBerry-maker RIM announced on Monday that it will use cell-tower triangulation as part of a new geolocation feature in its Locate Service for the BlackBerry Application Platform.
This tactic of using signal from nearby cell towers to approximate your phone's location is nothing new, and in fact, has been used as an ersatz procedure for finding your general coordinates for years.
As one notable example, Google has used "triangulation"--so-called since it used at least three towers to find your point on the map--in Google Maps on feature phones that lacked the much more precise GPS.
While the news is aimed at application developers, it also affects BlackBerry owners who use those apps that may be affected by GPS signal-loss.
It's a little strange seeing RIM adopt this less accurate fallback so late in the location game. To its credit, though, RIM emphasizes that program developers can look to cell-tower geolocation for quickly finding the user's basic whereabouts, and in truth it is a handy failsafe if GPS signals are blocked.
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1) It only uses the radio that's already turned on and must stay on by necessity - the cell radio. The GPS receiver is a whole other subsystem which can drain the battery in a matter of hours by itself.
2) Due to the nature of the GPS system, it can take anywhere from 30 seconds to 1 minute to get the info needed for GPS lock from power-on. See #1 for why you don't leave it powered on all the time. Many applications need a quick estimate of location (within a second) and kilometer-level error is not an issue. In those applications, its not worth the power drain and wait for GPS's accuracy.
3) GPS is far more accurate that cell triangulation most of the time. Other times, it can be wildly erroneous (e.g. locating you in the wrong state or country) and most units do a poor job of detecting and reporting that ridiculously-high error. Cell triangulation's best-case error is high but its worst-case error is far lower than GPS's. Most cellular/GPS systems do both and use the high but bounded error from the cell triangulation to detect and bound the worst-case error from the GPS.