Maps vs. GPS: If you're smart, you use both

You can get the surprise of your life when you use an online-mapping service such as Google Maps or Mapquest.

When I punched start and end points into Google Maps for a trip near Yosemite National Park, the suggested route included a Jeep trail that was built in 1916-17 to 1913 wagon-trail standards, has been closed to traffic since 1938, and now sits in designated wilderness open only to hikers and horses.

Heh, heh, heh. Good thing we knew better. Still, it's hard to believe a service that millions rely on could be so far off.

In advance of a trip, I often use Google Maps to calculate driving distances and time, then pick whatever route I feel like. I often try to avoid driving the same route twice.

Same with hiking. For a trip into Yosemite National Park, we decided to create a one-way route, to start at Cherry Lake in Stanislaus National Forest and end at O'Shaughnessy Dam at Hetch Hetchy Reservoir in Yosemite. So that meant we would leave my truck at the endpoint of the trip near the dam for a shuttle vehicle.

The back roads out there are a bit narrow, like most forest roads that follow ridges and canyons, but they've been paved for years.

Google Maps instead advised a Jeep trail that it said was 14.6 miles and would take 56 minutes. The adjoining map showed that it climbed up a ridge and down to Miguel Meadow, deep in wilderness, then traversed over a short ridge above Hetch Hetchy, then plummeted in switchbacks to the tunnel on the north side of O'Shaughnessy Dam.

That's right, you're supposed to drive through the hiker's tunnel. After all, it's been closed for only 74 years.

This story provided a few grins for our group. Others led astray have not been so lucky. Who could forget the heart-wrenching story of the death of San Francisco's James Kim? On a trip in 2006, the family, which included his wife and two small children, took an impassable road in a snowbound Oregon forest in an attempt to drive from Interstate 5 to the coast and got stuck. With no outdoor education, the family plunged into a series of errors. He died of hypothermia trying to get help; his wife and children survived.

The idea of depending on electronics as a safety net can leave you in a free fall. I always vet everything with detailed maps and love looking at maps and books. In time, you can learn to read the land, and in turn, how to find water, the best routes and the best locations for campsites with scarcely looking at a map.

On one recent trip, we left from the Onion Valley Trailhead, located out of Independence in the eastern Sierra, and hiked over Kearsage Pass and Glen Pass to reach Rae Lakes. About 150 yards above gorgeous Charlotte Lake, a guy stopped and asked for help. He showed me his electronic GPS map display, which showed the trail we were on, the lake and another trail (that didn't exist) that was supposed to go to the lake.

"I can't find the trail to the lake," he said. "Here it is on my GPS. But I can't find it. What do I do?"

I pointed at the lake, practically right in front of us. "Walk to it."

(Contact Tom Stienstra at tstienstra@sfchronicle.com .)

(Distributed by Scripps Howard News Service, www.scrippsnews.com .)