Misguided

It seems everyone who has an automotive GPS has a story about beingmisled by their e-nav device. Most are tales of annoying misses, ofbeing taken to the wrong side of town.

Some are dangerous: a few weeks ago a friend, returning from alate-night session at an unfamiliar bar, was guided home by his GPS.The route was accurate, but it took him through a section of Baltimoreone shouldn't frequent at night, one where, on this night, subhumanmorons started shooting at each other as he drove by.

Some are absurd. According to aweird news story I read recently,  a Gibraltar-bound truckdriver misprogrammed his GPS and was taken 1600 km off course. Turnsout there's a Gibraltar Point in England. One wonders how he got acrossthe Channel without noticing a problem.

Pretty dumb, huh?

Last month I was in Florida looking at colleges with my daughter. Wewere off the useful part of the rental-car map so relied on my phone'sGPS. It told us to drive 6 miles north on the Florida Turnpike, whichstruck me as odd. Wasn't our destination south?

But I complied and after 6 miles it told me to get off, make aU-turn, and head 22 miles south on the same road. Had I followed myintuition – that we were already north of our destination – we wouldhave saved 12 miles.

Pretty dumb, huh?

Yet what really would have changed? With no map the GPS was ouronly navigation tool. So we were helpless.

Except that not long ago no one had GPS. Other tricks, ones thathave worked for hundreds and even thousands of years, were available.Kristy could have asked someone for directions (being a guy, that's not an option for me ).We could have purchased a map, called the school, or stopped at a gasstation.

There's nothing new about blindly following the outputs of ourelectronic creations. A teacher recently complained to me that her highschool kids can't do arithmetic. Five times five? Sure, punch it intothe calculator and note that it's exactly 3125. The don't notice,though, that their nimble SMS-trained fingers missed the times (x ) button and hit y x .

Spreadsheet help us make thousands of mistakes per second.Unassisted a human can only achieve a somewhat pitiful few errors perminute.

That's progress!

I think one challenge we embedded people have is to check theresults we give. Though the calculator has no context to know whichbutton the user should have pressed, it seems reasonable that a navsystem could look ahead and see the inherent conflict in ordering oneto head due north and then due south.

I have pictures of big outdoor thermometers displaying temps like505 and -196 degrees, both impossible, on this planet, at least. Whydidn't the developers check the results for “reasonableness?” There'sthe digital parking meter demanding $8 million in coins, the antivirussoftware that warned the definitions were 730,400 days out of date, andoh so many receipts giving totals like “$9.9999999999”.

Stuff happens. We're not smart enough to anticipate alleventualities. Check your goes intas and goes outas.

But the user also has a responsibility to question data that appearsodd. That slide-rule order-of-magnitude sort of reasoning we relied onto guide us years ago remains important in the microelectronics era.

Jack G. Ganssle is a lecturer and consultant on embeddeddevelopment issues. He conducts seminars on embedded systems and helpscompanies with their embedded challenges. Contact him at . His website is .

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