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I remember reading about this when it happened and wondered how someone would follow directions like that. Then I was given one for Christmas and have learned to be careful in following the directions it gives.

While its usually right there are times it tells me to turn right to the location I’m going to when its actually on the left. I’m even noticed a 1/8 mile difference between the GPS location and the actual one.

They’re a good map supplement but not a replacement for common sense

How is using a GPS any different from, say, having my wife or my friend navigating for me from the passenger seat?

If my navigator says, “stop here” or “turn right” it doesn’t mean that I should stop in the middle of the road, or turn right onto the sidewalk. It means first pull over safely and then stop, or turn right at the coming intersection.

GPS position information can vary, depending on satellite reception and coverage. You are supposed to use a bit of common sense when using a GPS navigation device.

Having lived in an age where people managed to find their way around using maps, the current mindless reliance on the “talking box” amazes me. This is not limited to amateurs either. I saw a news story last month about small English villages that are plagued with large truck traffic on their narrow streets. The cause? Truck drivers just go wherever the talking box tells them to go, and often get stuck trying to manuever in the narrow lanes.

Sometimes I think if I invented a clever gadget (with flashy sound and video) that instructed people to send me money, I’d be rich.

Most GPS errors are not due to the GPS position being off but to the reference being off. For example, if your GPS says a road is 1/4 mile ahead when it’s right there, the problem is most likely not that the GPS doesn’t know where you are but that it doesn’t know exactly where the road is.

This comes from two forms of errors. The first is surveying error — if the manufacturer doesn’t know where the road is, the device won’t.

The other is compression. Manufacturers generally try to fit as much information on the device as possible given the capacity limitations and cost. To fit more roads, more points of interest, and more addresses, the manufacturer includes a bit less information about each.

This may mean rounding the position. It may mean omitting points where the road bends and treating it as if it were straighter. It may mean treating a number of houses as if they were in the same place. It may mean considering all the businesses inside a strip mall as if they were in the geographical center of the mall.

So the data in the box may actually, and intentionally, be imperfect. The solution is common sense — the GPS advises you, you need to follow the advice.