elevation gain issue

[rid-rider]

just took my ibike out for its first ride and had an odd elevation gain issue. a buddy was riding with me using an SRM PM. most of the numbers made sense between our two workouts except the elevation gain. his SRM reported 344 ft while my ibike reported 560 ft. Honestly I dont know what method the ibike uses to calculate elevation but expected these numbers to be much closer than what they were.

[arkiejon]

Just a guess, but you are giving the IBike a cold start where the SRM has already been warmed up so to speak being it is already mounted on the bike and been there all night where your IBike was in the house. I found it is better to take your IBike outside and mount it on your bike and let it set for a while to adjust from the inside to the outside (15 to 20 minutes). If I don’t let it adjust I will end up with a couple hundred feet more climb then descent. I found this fixes my wind calibration problems too.

[lorduintah]

The iBike sense air pressure - so weather changes can change the effective altitude. You can adjust the reported elevation with the software post-ride as one choice --- or during set up you can change to the current elevation you are at - assuming you have some way to know what that is - a GPS or a known value from Google Maps or various similar information.

Tom

[rruff]

My iBike's elevation changed 240ft since yesterday while sitting in the same spot.

[Velocomp]

Both the SRM and the iBike use barometric pressure readings to determine elevation.

Measuring elevation gain is surprisingly tricky:

1) how often the sensor is sampled is important. This is by my memory only, but I believe the iBike samples more frequently than the SRM

2) The sensor resolution is important. Again, by memory only, I believe the iBike's resolution is higher than the SRM

3) Even the "elevation gained" algorithm used in the firmware/software has an effect. For example, you'll find that the exact same iBike data, analyzed in iBike 3 software and in WKO+, will provide a somewhat different answer for elevation gained.

4) Lastly (though on the same ride this should affect different baro sensors equally) changes in barometric pressure will cause apparent changes in elevation. When a low pressure front comes through, there will be an indicated increase in elevation.

[racerfern]

My iBike's elevation changed 240ft since yesterday while sitting in the same spot.

Happens to me all the time. Perfectly normal as you go through the extremes of barometric pressure changes. I'm at sealevel so swings like that in pressure are very common. You just set your altimeter the next time you ride based on the conditions present at that time.

[rruff]

Mine started at 7330ft two days ago and is now at 6860ft in the same spot. Low to high pressure I guess.

[Russ]

Mines been over a hundred feet below sea level and didn't even get wet!

[lungbuster]

I have just spent 7 days in Bright, Australia, riding Mt Hotham (x3) and Mt Buffalo (x1) and various other hills and routes. My friend had a Garmin 705 paired to a PT. The iBike worked amazingly well and the difference between the iBike and PT/Garmin units was small. The difference in wattage was always consistent, my friend always about 30W more than I. I reset the iBike's altitude each morning or before each ride and there was ever only a small difference between the start and finish altitudes. For what most people need the altitude for the iBike works well. If you really need to be accurate go to your local map shop. Go the iBike!