What Do You Mean, I’m Driving In the River?

By Sharon Fisher, 8-03-09

We hadn’t asked for the GPS with the rental car—we certainly hadn’t paid for it, and we had our folder of Google Maps all ready—yet there it was. And while we’d used them in the past—what self-respecting geek hasn’t?—we hadn’t used them in several years and were curious about how the technology had improved.

The first time it sent us in a direction we knew was wrong, though, we were a little worried.

(Why did we rent a car in the first place? Because my beloved, be-bumper-stickered Subaru Outback has more than 200,000 miles on it, and the last time I drove to Tahoe in it, it waited til I returned to Boise and then blew a head gasket at Broadway and Myrtle. We figured it could use the rest.)

The route was simple—Boise to Tahoe. 84 to 55 to 95 to 80. Got onto 84 and exited at Midland, the exit created with the new shopping center out there that dumps you onto Karcher at Nampa-Caldwell Blvd. Karcher becomes 55.

That’s where the problems started.

“Please return to the highlighted route,” the GPS said.

Buh?

Apparently the underlying map data didn’t get updated after the creation of the new exit, even though it happened a couple of years ago. Fortunately, *I* knew what I was doing and where I was going, and I continued on, while the GPS continued pleading with me to do what it said, even showing me where I was located and the bright pink line I should be on instead.

However, it recalculates itself every few minutes, and soon figured out that, somehow, against its instructions, I had managed to figure out how to get to the right place, and we went on without further incident.

Until we Changed Our Minds.

We’d each heard about an alternative route through Fallon that lets you circumvent Reno on the way to Tahoe, and were curious about trying it out, so we looked at the paper map and figured out what we’d need to do, and headed off.

The GPS, however, was having none of it.

“Please return to the highlighted route,” it insisted, telling us to make a U-turn.

We ignored it.

“Please return to the highlighted route,” it pleaded.

We continued to ignore it. Actually, at this point we were curious to see how long it would take to figure out what we were doing. It was like sneaking out on Mom and Dad when we were teenagers.

“You know, I don’t know why I bother,” it said. “I work and I slave, and what thanks do I get?”

Okay, I made that last part up. We were wondering whether it would get more insistent as time went on, but it did, eventually, figure out what we were doing and let us do it.

Actually, it turned out to be pretty helpful in some parts of the trip, such as getting out of downtown Oakland and winding our way through downtown Sausalito on a beautiful July Sunday. As we drove up the California coast to Eureka, then to Eugene and to Portland, it was a reasonably reliable, helpful companion, never saying “Well, I don’t know where the hell we are, I told you to ask directions twenty miles ago” or any of the other things that navigators sometimes say. Occasionally we’d jump out of our skins when, after a couple of hundred miles of silence, it would suddenly say, “Right turn in two miles,” but we got used to that. We started singing along with the little tones it would make to indicate right turn, left turn, go straight, and U-turn.

Then we got to Sauvie Island (a beautiful oasis in Portland and if you’ve never been there you should go immediately, but I digress). There we had a bit of a problem.

At this point, it’s important to stop a bit to explain how GPS—Global Positioning System—works. It takes signals from a variety of positioning satellites and uses that to triangulate one’s location. Consequently, one needs to be able to receive signals from more than one satellite at a time. To crib from Wikipedia:

“It might seem three satellites are enough to solve for position, since space has three dimensions. However, even a very small clock error multiplied by the very large speed of light—the speed at which satellite signals propagate—results in a large positional error. Therefore receivers use four or more satellites to solve for x, y, z, and t, which is used to correct the receiver’s clock. “

Yeah, okay.

So whenever we turned on the car, the GPS would start by first gaining access to four satellites, and then giving us the map. But for some reason on Sauvie Island, it couldn’t find enough satellites, and when we got a map at all, it was....off.

See, Sauvie Island is surrounded by water. This is typical with an island. That’s why they call it that. So when the GPS couldn’t reach all its satellites, it did the best it could.

This is why it showed us blithely floating up the Columbia River, and directed us to continue doing so.

Not being equipped with floatation devices, nor a paddle, we persisted in driving on the road, despite its attempts to guilt us out with its patient “Please return to the highlighted route.” We wondered whether this was its payback for refusing to follow its advice around Reno.

Other times, instead of showing us on the mighty Columbia, the tiny pink triangle depicting our car was located in a black void, with no roads to be seen anywhere. We started arguing over which of us got to be Major Tom.

We managed to make our way back to suburban Portland all by our little own selves, not even needing to resort to the humiliation of calling the friends with whom we were staying to ask for directions.

Fortunately the next time we started up the car, the GPS managed to retrieve enough satellites to display our position correctly for the trip back to Boise, where we returned the car without incident. We did wonder, though, whether the little turncoat would get even with us by tattling all the times we were speeding on 84. I’m sorry, Pendleton to Baker City is boring, sue me.

But I miss it sometimes, in the same way one can miss a nagging spouse. It seems awfully quiet in my car these days.