As you can see, the altitude line is basically level but wiggles a bit (and I wish they'd get rid of the drop shadow on that line - it's pretty but it makes it a little more difficult to read the curve - more chartjunk!). How much does it actually vary? Well, running my cursor back and forth and back and forth and back and forth and back and forth over the curve, the highest value appears to be 1489 feet on 3/5 at 11:10, and the lowest value appears to be 1309 feet on 3/5 at 1:40pm. In other words, by the plot the sled lost 180 feet of altitude in 2 1/2 hours while sitting still.
So, what's really going on? A couple of possibilities:
- The tracker is using barometric pressure to measure altitude, and this is due to normal fluctuation or weather changes. Not likely
- The GPS in the tracker is triangulating altitude, along with lat/long. This tends to be much less reliable than GPS lat/long readings and can fluctuate amore, and is the more likely explanation
[n.b. note that IonEarth will redraw the "analytics" while you're looking at it, taking it back out to the full scale even if you've zoomed in. Thanks tons, guys - your stuff is a pleasure to work with.]