Different total ascent? Underestimated by Edge 830?

My 830 consistently records approximately 10-20% low in comparison to the mapped Strava route and Garmin route. To be fair my old 820 used to do the same, not much has changed. Strangely enough both devices always depicted the correct elevation when at known waypoint elevations pretty closely. 

I'm not sure which is more accurate here, but keep in mind that Strava and Garmin are using a DTM digital terrain model underlying their map. This can be quite coarse and sometimes incorrect. Whereas your Garmin device is probably measuring the change in air pressure. I can't imagine this being that accurate especially if the are big atmospheric changes while you are riding.

I don't know if this accounts for the differences you are seeing, but I would be suprised. Looks like a great ride though!

If you want more accuracy, seems like you should manually set your current elevation before you ride.  That would likely help some.  Pilots do that all the time on their altimeters.  And when you leave that plan sit for a day or more, it needs to be reset. Every time.

If you want more accuracy, seems like you should manually set your current elevation before you ride.  That would likely help some.  Pilots do that all the time on their altimeters.  And when you leave that plan sit for a day or more, it needs to be reset. Every time.

That never helps. I have saved my home elevation and the unit said calibrated everytime I started. However, the total ascent is never accurate if my route contains a lot of fake flats. My two 830s (second one is a replacement due to the battery issue) are more or less the same problem. The insensitivity of the small elevation change indicates that the barometer in 830 is a low-accuracy one and the interpolation algorithm is quite shXt.

Check out the 6.20 update now available.  It claims to address some elevation accumulation issues.

However, it's worth noting (as others have done on other similar threads) that you don't really have a gold standard for comparing the elevation numbers.  If you planned your route on Strava, and then used Strava to "correct" your numbers, I would expect them to agree.  But perhaps your Edge 830 is correct and Strava is wrong, or they are both wrong.  

There seems to be a question about the Strava elevation data (from satellite data? from maps?) and I wonder if you loaded your route into some other route plotting system if you would get yet a different answer (particularly if their source data is different.)

At least I find that the barometric data provided by the 830 is consistent and repeatable in a wide variety of climatic conditions (e.g. Winter vs. Summer).

I used to have another head unit, which gives me a total ascent usually between the strava number and 830 number, but much close to strava number. Though that unit is less fancy and the software is near to zero, the barometer is much better. Its grade changes more rapidly and close to reality. Even compared to old 800/820 used by others in the group ride, when most others showed 16% grade in a 50m steepest part, my 830 only showed 13%.

6.20 is claimed to fix the elevation issue in 6.00, in which the elevation line is smoothed way too much and my unit is still 5.50. However, the inaccurate/undersetimated total ascent problem exists since the first release of 830 (I pre-ordered 830 on wiggle). I won't touch a new FW unless there are only a few problem feedbacks after several weeks.

Just got 6.20 on my 530 but have been getting elevations for past month. If unit is sitting at 145ft I've watched it drop to -200ft in my 2nd fl nyc apt. Again, just in the past month. And it also has me descending when ascending a 5% 1mi climb.