Cellphone GPS won't always help your rescuers

BACKCOUNTRY adventurers often carry a cellphone, not just to call for help in an emergency but also to allow rescuers to home in on their location when things go wrong.

But recent incidents in the North Shore backwoods have underscored the fact that relying on it for this purpose is far from a safe bet.

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North Shore Rescue volunteers have twice in the last month gone in search of folks lost in the backcountry only to have their GPS or triangulation locations point the team to the wrong place - many kilometres away.

On Feb. 29, rescuers picked up two skiers who got lost near Mosquito Creek after taking a wrong turn off Grouse Mountain's Skyline Trail. The men used a cellphone to call for help, and rescue volunteers went out looking for them, but not where the phone's GPS locator placed them - Vancouver's West End. An RCMP helicopter had to spot the men the old-fashioned way and direct a ground team to their location.

Three days later, two men called West Vancouver Police after getting lost near Nickey Creek coming down Hollyburn Mountain. Volunteers were able to find them by following their tracks in the snow - far from the Vancouver address the phone's GPS suggested they were at.

"When a guy's lost in Hollyburn and his co-ordinates show up in the West End, you don't go to the West End," said Tim Jones, rescue team leader.

"We've had this happen before. We had a lady who was stuck in Crown Pass, a diabetic who was really in trouble, and her co-ordinates put her right off the ocean where the ships park near Jericho."

How well location-based services on cellphones work depends on a number of different things, according to Shawn Hall, Telus spokesman: What kind of phone you have, who your mobility provider is, and where you are located.

"The ability of the technology to locate you is really dependent upon the weakest link in the system," Hall said.

Most older phones don't have GPS technology, meaning rescuers can only locate the source of its signal by using triangulation. In a best-case scenario - when the phone is in range of at least three cell towers - triangulation can pinpoint a person's location within 200 metres. If only one tower is nearby, the signal could appear to come from anywhere within that tower's range.

If a phone has a GPS system, a satellite can locate it within 50 metres, but that too is only under ideal conditions. Buildings and mountains can throw the location off.

While having a cell phone in the wilderness can be lifesaving, Hall said it shouldn't be viewed as guarantee you can be easily found.

"If you're doing a lot of backcountry hiking, it's probably better to not rely on your wireless as your only and primary means of location in an emergency," he said.

Instead, Hall suggests using a personal locator beacon, which has a dedicated GPS link. Beacons retail from $20 to $600, depending on their quality and features.

newsroom@nsnews.com

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