|Astronaut's wings and other silly goals ...||Humma Hah|
Nov 11, 2001 12:54 PM
|For a while now, I've been toying with a nutty idea of setting climbing goals in addition to mileage goals. This year, if my altimeter is to be trusted (it is NOT), I've climbed close to 200,000 ft. That's getting up near "the boundary of space" at 50 miles, the point at which the Air Force passes out astronaut's wings. I'm sure many of you have well passed that mark this year.
I'm wondering if such an award could be issued, for example, in brevet runs. Those runs must have a certain minimum amount of climbing, and they generally know the amount of climbing per ride. Finishers could accumulate altitude as well as miles, and receive awards as certain milestones are passed. 100 miles and 200 miles would be goals, and sufficient extra climbing to account for enough energy to have accelerated to orbital velocity or escape velocity would be even better.
|I know that altimeters in little bike toys are not terribly||bill|
Nov 12, 2001 8:08 AM
|accurate, but I was on a recent ride where my altimeter registered 8,000 feet of climbing and others registered 5,000, and everything in between. Do you think that it was because mine was more sensitive, adding up little rollers as well as real climbs in the total, or was it because mine is just terminally stupid? On my normal training ride, on a loop that involves like one hill but lots of little ups and downs, my toy usually comes within about 50 feet of itself (1300 feet in twenty miles). What actually happens is that I live probably about 400 feet above seal level, I descend nearly to sea level (along the Potomac), and then climb back up. |
I know that they register changes in air pressure, but does anyone know the accuracy of these things?
|Pretty good, but..||muncher|
Nov 12, 2001 8:18 AM
|They are not altimeters per se, but barometers reading in height.
I have a hill walking friend who has one of these on his watch. It's very accurate (as against known points on a map). However, what throws it is changes in datum over a journey, i.e. barometric pressure changes over time/distance v height. So the barometric pressure at the end of the day at your startpoint may not be the same as when you left, or of course, you may finish in a different place where the pressure is different. That causes the sensor to "tell you" you are at a different height, as it's reacting to a different pressure.
Doesn't explain the vast differences you mention between yours and your friends though - were they all set the same at the start?
|Don't know. I actually never have "zeroed" mine; I don't really||bill|
Nov 12, 2001 8:35 AM
|care about absolute altitude, and I always thought that the variation caused by the factors you describe would defeat whatever we were trying to accomplish by agreeing on the starting altitude. All I ever cared about was relative altitude, although it occurs to me that the barometric differences being measured may not be linear -- do you know whether, if I'm starting at sea level but my altimeter reads "200 feet," is the total climbing reading affected? I've always assumed that pressure varies in direct mathematical relation to altitude, but maybe it doesn't.|
|It's not quite linear...||muncher|
Nov 12, 2001 8:47 AM
|I can't recall the exact lapse (pilot's exams many years ago - pass exam - brain dump of that sort of "trivia") but the varience from linear is prob way too small to affect us here.
The point I didn't bring out too well was the if at 0900 the pressure on your drive is 1000 mb (for sake of example) but at 1700 is 1010, you will not be at the same height on your instruments, even though you actually are, and similarly if you cross pressure differences on your journey, your climbing readings will be skew. The real life effects of this may be small or large, depending on where you live/ride, and the time of year.
|Very susceptible to tiny pressure changes...||cory|
Nov 12, 2001 8:48 AM
|Mine used to drive me crazy, showing variations of 40-100 feet over the same short ride. Then a pilot friend pointed out that we're asking a $100 toy to measure elevation changes of 20 feet or so--going from the first floor to the third floor of a building--but we DON'T want it to notice when the ambient pressure changes. Best solution I've found if you want an accurate measure is to zero it often. My house is at 4910 feet, but I've had readings from 47 and change to 5100+. I just set it when i leave the house and trust it for the rest of the day.|
|Well, of course. You've got to make sure that the house is||bill|
Nov 12, 2001 9:01 AM
|going to be there when you get home. |
Nothing worse than coming home from work, and all you want is a beer, the leftover meatloaf, and a little bit of CNN only to find out that your house is buried 4000 feet below you or, maybe worse, hanging just above the cloud cover.
|Don't worry, won't happen...||muncher|
Nov 12, 2001 9:10 AM
|because you are under the same pressure as your house (so long as you are out riding, and not at work) therefore, you will arrive at the same height as your house, even though it's lower/higher than when you left. Just don't step outside without looking down first. In fact, as long as you have the altimeter with you, you will read the same pressure changes as the surrouding area, and thus, will have no relative falls/gains in height at all. Therefore, you can climb all day without noticing/feeling it :-)|
|I have new respect for my little toy. nm||bill|
Nov 12, 2001 9:17 AM
|A weak battery will do it ...||Humma Hah|
Nov 12, 2001 5:44 PM
|This summer I rode a little flat century, should have maybe racked up 3000 ft, but the altimeter registered over 12,000, a pace that would be comparable to the Death Ride. It had been sporadically reading high on my daily rides, known to be about 1000 ft of climbing.
Turned out the battery was dying. A fresh one fixed it right up.
The position of the "static port" can affect it, too. If the air-pressure-measurement port is in a position to take a pounding from the wind, that can cause a lot of small altitude variation readings that add up false climbing. I've seen mine read a little higher on days with frequent hard wind gusts.