A few weeks ago I bought a watch with a built in GPS, so that I could get exact running distances even when I didn't go on roads. It is my understanding, from speaking to colleagues, that GPS requires three views of the sky (which presumably has satellites in it) to determine global position (I find it interesting that although one only needs two pieces of information to determine a point on a sphere, GPS uses three satellites, effectively not using that you are on earth). The three views of the sky restriction is important to me because my watch loses my position when I run under dense foliage. It will interpolate the distance I ran when I come out of the foliage (assuming a straight line) but the resulting gaps shorten the total distance it reports at the third significant digit. The variation is larger the faster you run (see Heisenberg, although I think it is absurd that this effect would be observable here). I find this particularly annoying when timing my favorite 5k loop, in which I wiggle though some trees in a park, and get distance measurements from 3.02 and 3.09 miles for the same run (which according to gmaps-pedometer is 3.106 miles).
New Years Update: I weigh a daily average of 184lbs with a morning/evening variance of 3 lbs. I am calling this a resolution officially resolved.
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