[pct-l] GPS and Pi

[csiechert at hotmail.com (Carl Siechert)]

> -----Original Message-----
> From: SnoLepard
> 
> Even if two hikers walked around the Earth at the equator, 
> one on the ground and one on a wall three feet high, the 
> hiker on the wall would still only hike 19 feet farther.

You're right, and if the inside hiker and outside hiker complete a
cumulative turn of 360 degrees during their hike, whether it's 31 miles
(around the 10-mile mountain) or 26000 miles (around the Earth), outside
hiker goes only 19 feet further than inside hiker. So your implicit point
that no matter where you drive the measuring wheel along a three-foot tread
width, the difference in measured length is insignificant, is true. AS LONG
AS you only have a 360-degree rotation during the course of the day.

But each switchback turns about 300 degrees--so you could have a 16-foot
measurement variance (6 x 3.14159 x 300/360) on every single switchback. On
a trail with lots of switchbacks (say 20 per mile, with each leg being ~260
feet), that cumulative variation alone could account for a 6 percent range
between the inside and outside measurements.

It's hopeless!