Elevation problem

Former Member
Former Member

HI

I did read a lot of discussion here:

elevation-consistently-inaccurate-reading-too-low

problem-with-barometric-altimeter

altimeter-issues-in-the-rain

Looks that I am not alone who has problems with elevation. Problem which happen in my case is ONLY during activity. I also think that there are several different problems.

#1

I did check pressure and elevation graph in watch during the day (holding ABC and scroll), values were OK. I did compare pressure with my weatherstation and very close national weatherstation. I did stay at home during all day so altitude was same but elevation in watch change a little (+-5m).

I did start mtb ride at 5:30pm and for 1h ride I did make cca 17km. I did make several small up and down hills. Before I did stop activity I did see that elevation is not correct because I did start and stop almost at same place.

Here are graphs just after I came home:

you can see that elevation at the end is higher. I did start at 228m and stop at 264m.

pressure graph, I was SHOCKED, how pressure can change so much, cca from 1016 to 1022. I did find out that it happen during descent.

I did check my local weather station:

I also check national weather station, and there is also nothing strange. I did put marks to be able compare with watch 6 hours graph. I think, there is something wrong with sensor or with firmware of Instinct.

I did export activity to GPX and then enable elevation correction in web and export that too. Here is comparison

Blue is original GPX with elevation based on barometer. Green is GPX which has elevation correction enabled.

The significant change start at cca 0.55h = 33min of ride during normal descent.

In other threads someone mentioned sweat can make some problem. And there is also thread where rain is mentioned. Do you think that this can be problem in my case? It is 4 hours after I finish my activity now. Watch still showing wrong values of pressure and elevation. If it is problem of sweat or water then how long it takes to dry? or is it going to correct itself?

#2

What I also know is that instinct is slow in elevation reading.

I can see that in fast descent. Another day I went slower on downhill and also slow down before next uphill. Results was quite OK. Of course, barometric altimeter will not catch all small hills.

Settings:

- altimeter auto cal = off

- barometer watch mode = auto , Tell the true, I don't understand this settings clearly.

thanks for any comments

  • Former Member
    0 Former Member over 2 years ago

    UPDATE #5

    I went for small ride with children after lunch. After that I decide to go for ride. It was 3:30pm. I already knew that today ride will be disaster because I did see wrong altitude at some place during the ride.

    Ride 126:

    Problem start at about 6.5km. OK, lets check this chart in time.

    This is pressure chart cca 1h 10min after I did stop activity

    That's pretty strange. Lets check my local weather station.

    Ride 125 which was almost perfect. So check local weather station for ride 125

    Well, I think that my today descent {ride 126 at about 6km} was to fast, so pressure change was similar as pressure drop cause by weather. Watch start to think that I am in different altitude.

    1h 10min after activity stoped whatch is still thinking that I am at 245m altitude but I am at 216m

    I am doing MTB rides for joy. I did track my rides with phone and Locus map app. But GPS accuracy, specially altitude is pure. So I decide that I will buy cycle computer with barometric altimeter. I did find out that If I put little more money I can get this watch. I did finish today ride with sad mood. My conclusion is that I will not use something what is making me sad.

    I already talk to shop where I did buy instinct cca 2mouths ago. It is not possible to return watch and get money back. They can only send watch to garmin as RMA. Hope they will find bug in firmware soon.

  • Former Member
    0 Former Member over 2 years ago

    UPDATE #6

    I decided to not use gadget for today Ride 127. Here is elevation profile. Again, BLUE is original using barometer altimeter, GREEN is same track with enabled elevation correction on garmin connect web.

    And here is pressure chart after cca 1h30min activity stoped.

    I did also write to [email protected]om {Danny is mentioned that in his comment https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/instinct/170598/elevation-smoothed/933417#933417 }

    AND I hove got answer. So will discuss that prolem and hope they will make something to solve this situation.

  • Former Member
    0 Former Member over 2 years ago

    I did check all (well, not all but 95% some of them are just ride with childrens around vilage) of my MTB rides AND compare original elevation gain with gain when "elevation correction" is enabled (that is enabled for garmin devices which has not barometric altimeter). It is quite "clicking" work. Later I find out that I should also compare elevation loss. That's it compared on last rides.

    E = C / D

    H = F / G

    Here is table: (EDIT: I did updating this by adding newer rides)

    As you can see that watch has firwmare version 2.40.0.0 when I bought it.

    It's a pity I didn't do more rides before the update.

  • So, I have made tests.

    HR is not affected by the cover. The thickness is about 0.7 mm.

    Unfortunatly it was not so warm and the sweat was not so much, but the cover works very good and there is no sweat in the barometer hole.

    You can order it here with optional colors.

    https://www.shapeways.com/product/KYQHLAD8F/garmin-instinct-barometer-cover?optionId=121901926

    Regards

    Thomas

  • Thank you very much for your contribution!

  • Former Member
    0 Former Member over 2 years ago

    UPDATE #7

    I went for ride 128 without gadget again. Result is very interesting.

    Here is result

    BLUE line is original GPX. GREEN is made by garmin web connect with enabled "elevation correction". Both GPX are exported from garmin web connect.

    Lets say that first 3km is OK. Then barometer altimeter is off. Surprise, it get correct later between 13.5 and 16km.

    Comparison elevation gain and loss is almost ok, barometer altimeter is 90% "elevation correction version".

    Here are charts cca 1h30min after activity stoped.

    Conclusion: looks that it is more software problem that "design" problem.

  • I would say the two graphs are close enough for me. If I wanted precise altitude measurements, I would use another device. As a sports/fitness device, it all looks good.

  • Former Member
    0 Former Member over 2 years ago in reply to DJGShef

    yes, but check my comment with table with my MTB rides. Only 6 from 30 rides has so close (90%) elevation gain and loss. That's pretty sad.

  • Former Member
    0 Former Member over 2 years ago in reply to Former Member

    To make a comparison with your graphs, you need your start and stop barometric readings.  Better yet, is to note the barometric pressure at specific timelines (every 30 minutes or so depending on the length of your ride).  If you ride into the wind and get a gust, the barometer will pick that up as an elevation change.  If you compare barometer changes against elevation correction (which doesn't factor in barometric changes) you'll most likely see where the discrepancy is taking place. A minor .05 inHg change in pressure is roughly equal to 50 feet of elevation change on your altimeter. 

  • Former Member
    0 Former Member over 2 years ago in reply to Former Member

    yes but manual is saying that AUTO will take care about that.

    https://support.garmin.com/en-US/?faq=qyfmQF7Au284m7pXMi5ie9&productID=621802&searchQuery=Barometer&tab=topics

    I think that you are talking about "altimeter" mode.