Pondering Altitude

We ran up and down a hill three times yesterday. And my GPS watch recorded it.

As you can see, the hill got lower each time we ran it. But the bottom of the hill also got lower. The elevation change from top to bottom didn’t vary as much, staying about 200ft. The first time the top was at 306ft and the bottom at 102, the second time 248-72ft, and the third time 228-36ft. Samples were roughly 26~27 minutes apart.

It’s amazing how fast the earth’s crust changes around here.

Perhaps even more interesting, the lowest point was about a quarter mile from the start, so it should have been hit twice between peaks (with about a 50ft mini peak between low points), yet each lap appears to have only one such.

The USGS topo map claims that the top of the hill is at ~240ft, and the bottom is at 120ft. MapMyRun draws a very fuzzy graph which shows the top below 300ft and the bottom above 50ft.

Perhaps I should go back with an old fashioned altimeter. Would dGPS help any?

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2 Responses to “Pondering Altitude”

  1. Dave Says:

    Under the assumption that you didn’t spend any significant portion of time levitating, you can correct for this by taking the DEM z for your GPS measured x and y. (I believe this correction is so common that it’s even in the public google maps api) During a training, yes, it’s nice to have an altimeter.

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