x43x

I tried out my new cyclocomputer that has an altimeter in it. Who knew something so trivial good be so fun? Its seems pretty accurate too. Going up slight grades registers a +1%. The 20% grade near my house showed up as 24%, so I wonder if their sign is off. And it was reassuring when I got back home and the altitude was exactly the same as when I started.

Somewhat unrelated, but when I sat down at the computer to input some stats I noticed there is some wireless wormhole at my desk. There is a four inch space on my desk that when the cyclocomputer is in the space, it registers as going 59-60 mph. When I move it out of the area, it goes back to zero...really weird. I'm running wireless internet so that could explain things, but why would it just effect that small area?

DrPete 

What computer/altimeter are you using that gives you % grade?

therealsybarite

those things are relatively accurate, but i wouldn't suspect that the sign is wrong. as far as i know they all work on pressure. if the atmospheric pressure changes your altitude readings will change as well.

mayukawa

Not sure what OP has, but I also recently got a one with altimeter (a VDO MC1.0) that shows the percentage grade. The grade is calculated on a 12 second interval averages, so if you're going up and down within that time or close to that time, the grade doesn't seem accurate.

sogood

So the idea is not to fly up that hill but take your time... Lots of time.

x43x

I got the VDO 1.0+. Its pretty awesome. I was contemplating that or the Edge 305, which was too big for my tastes, and a little more than I wanted to spend. One thing it doesn't have is cadence, which is fine for me.

mayukawa

Wish I can fly up the hill, but I've been off the bike for more than a month. My in-season average speed up San Bruno Mountain is usually 11~12mph, but I just tried it on New Year's day and I was averaging a miserable 6~7mph. I was planning to do 10 up and down trips, but my legs started to cramp after 5 laps (~5500 feet).

ROJA

Garmin Edge 305 gives you grade.

mayukawa

I haven't taken off my Cateye Astrale 8 yet, so I have cadence. I might just keep both of them on. As you also have a MC, have you noticed any oddities with yours?

I noticed a couple of weird things on mine. On a certain stretch of San Bruno Mountain (for example), it would register 7% going up, but when I zoom down the same segment, it might only read -4%. I'm thinking it's due to the 4-second samples and 12-second averaging intervals, but that was a relatively long stretch of road. I wonder if it compensates for Bernoulli's Principle?

A second weird thing that I've noticed is that the elevation readings seem consistent within a certain time period, but not if they're separated by several days...despite setting the home elevation each time. I've only tried this twice. I set my home elevation (30ft above sea level) than climbed to the peak of San Bruno Mountain. The first time I did that, it said the highest point was 1259ft. The second time I went up to the same spot and it indicates 1305ft. Both readings are slightly higher than the elevation reading given by Google Earth. I know GE isn't that accurate either (I've checked). I wonder how many bits the ADC for the pressure sensor in the VDO is? Opps! Never mind, I guess that can be calculated from the elevation range given in the manual.

tbdean

Blackburn Delphi 6.0 gives % grade.

I love it. I can see speed, heart rate, trip time, and cadence all on one screen.

x43x

I noticed it was a little delayed in getting the info when decending, but seemed to be consistent with the climbing effort. I've only done the one ride so far, so I can't comment on all the different oddities. I think I read in the manual that temperature changes will effect the barometric reading and needs to be recalibrated using the Home Altitude. I was just happy that the start and finish altitudes were the same. Reading things about the Garmin, I was hoping to avoid oddball readings. We'll see if things get strange with more miles.

Phantoj

Is that the one you posted a picture of last year? I've been commuting home through that area lately... that hill is steep!

Maybe the 20% is an average grade over a longer distance.

x43x

It is indeed. It's only a block long, so it's not too great of a distance. I'll try it again soon and see if I get a different reading.

Pico

Uncoded wireless computers are can get interference from all sorts of things. I had one that would register about 60mph if I had it near my laptop. They can also pick up signals from other riders if you're in a group.

Doggus

Yes I love my Garmin Edge 305 altimeter. It regularly shows I have about 200 feet of climbing in 1 hour on the rollers. If I didn't use the Edge, I wouldn't get any climbing done in my living room.

mayukawa

I don't think altimeters work well indoors. I have all kinds of readings going up and down between the 1st and 3rd floors. Someone can open the door and the reading would change. Regarding the interference, I read on VDO's website that they're still using unencoded, analog transmission, so that's why I got the regular wired model-->so there's no weird speed readings. One funny thing I find "strange" is that VDO touts about German precision engineering...but their speed readings are in .5 kph/mph increments...while I can get a <$10 cyclocomputer that has .1 kph/mph increments...

x43x

The .5 increments is pretty lame. What is weird though, is the Avg. Speed reading shows measurements to the hundredth, but only the tenth place changes, in increments of .1, and the hundredth stays at zero. Silly Germans.

There is a Vetta computer with an altimeter, but the display only shows 2 things at a time and it's more expensive than the VDO. It does have the capability of wireless speed and cadence, but then the price is up there with the Garmin.

sogood

Units like Edge 305 use GPS data to regularly recalibrate their barometric based altimeter (lots of averaging of the GPS elevation reading). Indoors, the changes in the elevation reading is largely due to changes in the atmospheric pressure over time. Effectively, you are running a barometer.

x43x

Today I did a short, flat ride and the altimeter gave some weird readings. The weather was pretty wacky though, so hopefully that had something to do with it. When I started it was dry and breezy, but an hour later there were stong winds and sideways rain, with a slight drop in temp. The altimeter showed about 40ft when I started and got all the way up to 112ft. I checked Google Earth and they showed the start at 26 ft, and the highest was about 55ft. On the way back the elevation only went down about 20ft, so there was a discrepancy when I got back to the starting point.

The tail wind was so strong that I was able to hold a 25 mph pace for several miles and at one point got to 31 without much effort at all. Riding into the wind at 16mph was less than exilerating however.

lennyk

does it have a little hole for the air pressure reading ?
you may need to make sure that hole is not getting any air blowing into it directly

biffstephens

Me and my girlfriend rode today..she has a Garmin 305 that she uses for training. She has been uploading her stuff to MotionBased.com lately..

It is pretty cool what they give you with your data....

https://trail.motionbased.com/trail/activity/1876371

aicabsolut

Does it say you have satellite reception in your home?