The Mystery of GPS

GPS gizmos are the new Xboxes for cyclists.  Map out your ride, save your route, measure your climbs, record your distance, share with friends….and Strava–how can you beat the idea of virtual racing against cyclists you’ve never seen?

Howie and Bill R. mystified by GPS?

Which brings us to the question:  does GPS really know what we think it knows?

Exhibit 1:  I recall sitting in the car on a country road outside of Franklin, NC, not too long ago watching cows peacefully graze in a pasture while our Garmin insisted that Walmart was right THERE!

Exhibit 2:  After a loop-ride through mountains, why are “elevation gain” and “elevation loss” always a different number?

Exhibit 3:  Why does think our Day 5 route climbs 1833 meters (5,957 ft) while thinks the same route climbs 2829 meters (9,194)?

In fact, biketoaster and ridewithgps disagree on EVERY Italian route elevation gain that I’ve mapped.  This is disconcerting.  Not only because 9,000 ft. hurts a lot more than 6,000 ft., but because it calls into question science, engineering, computer programming and the military.  Is GPS real?  Is it astrology instead of astrophysics?

We’re told that GPS relies on data from a constellation of satellites strategically located in the stratosphere, and satellite triangulation can pinpoint a location to within 4′.  If that’s true, measuring the distance between the bottom and top of a hill should be no problem.

Which makes me wonder, is it the earth or the satellites that are wobbling?  The earth DOES wobble, but could that account for 3,000 vert. feet in 57 miles?

This is a fundamental mystery we are setting out to solve this year.  I’ll keep you posted.  Meanwhile, please, geeks and astrophysicists and general armchair theorists, comment with your thoughts.

It would mean a lot to us to know the answer BEFORE we climb 9,000 feet!


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