Computers - what are the altitude increments?
 

I need a new computer and my old wireless Cateye's have always been fine for my needs.

Top top: don't leave them in storage if mice are present... little critters love the rubber buttons!

So I was wondering, how accurate the altitude/elevation function is on those that feature it... or rather, what are the increments? 5m, 15m, 50m?

If they only register change every 50m, for instance, I won't bother, but it would be a fun thing to have if they are more sensitive.

Almost forgot to ask... which one do you recommend... either with altitude/elevation or without (in which case I draw the line at cadence and HR... don't need either). I like the look of Sigma Sport or Cateye.

I am not sure how often it recalculates, but mine can indicate any number of feet climbed, so I guess the increment is a foot. Since mine is barometric, it is usually fairly close to the folks who ride with gps, but if the weather is really variable, that accuracy drops considerably. However, where i live, there aren't that many occasions where the pressure drops or increases rapidly.

I believe the Garmin 305 and 705 have a resolution of at least 1 m.

They may have a display value down to a number, but I'm very skeptical they are precise and accurate to that level. A GPS system is not that good by far for altitude and a barometer-based altimeter is subject to errors caused by variations in the air pressure, as others have mentioned already. If you get one, it'd be fun to ride the same course several times and compare the elevation profiles from the device.

But if you upload your data with it via Garmin Connect the website has a feature to apply elevation correction to it. Where it throws out the device acquired elevation data (via GPS) and looks up the known topographic data from all the latitude/longitude points along the trip.

And for the devices with barometric data(Edge 500 and maybe 705?) you can actually set 10 known elevation points in your device. So for example you could set the known elevation of your house and the device would then be able to use that as a reference point to make adjustments to the elevation data based on barometric pressure. This should pretty well minimize any error due to weather related barometric pressure changes.

http://connect.garmin.com/activity/35269746
(5 days apart)
http://connect.garmin.com/activity/35675543

Not perfect by any means.

My barometric one is pretty accurate if properly calibrated.

It sounds like your real question might not be so much about how *accurate* it is, but rather how *sensitive* it is. The barometric altimeters are quite sensitive and will register changes of a few feet. Definitely significantly less than 5m.

How close the reading is compared to your actual elevation depends on how much barometric pressure changed after you last calibrated it.

Cadence and HR are pretty useful. I like my altimeter because it helps you plan your effort on climbs -- you always know not only the distance from the top, but how far you have to climb. Also, knowing the slope is sometimes handy since it confirms why you are suffering.