Elevation problem

Former Member over 5 years ago

I did read a lot of discussion here:

elevation-consistently-inaccurate-reading-too-low

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.

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?

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

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0 Former Member over 5 years ago

UPDATE #8

Ride 129 is bad again. I did not used gadget.

Just after I did stop activity.

0 Gregor K. over 5 years ago in reply to Former Member

Yesterday calibration, today

0 Gregor K. over 5 years ago in reply to Gregor K.

Same elevation on start and stop. I started outside and stoped on the 2 flor.

0 Former Member over 5 years ago in reply to Gregor K.

Gregor K. said:
Same elevation on start and stop. I started outside and stoped on the 2 flor.

how did you configure "watch mode" of barometer? did you choose "auto" or "altimeter" or "barometer"?

0 Former Member over 5 years ago in reply to Former Member

No, I read you were using auto mode and that's what I'm referring too. Your watch has no idea if you just ran on a hill slope or if a gust wind hit you. It does nothing more than guesses when in auto mode as to what made the barometer change. Sometimes it's right, sometimes wrong and sometimes it's way off. For example, I was in Las Vegas in August when the ambient temperature was 109 degrees Fahrenheit and I was walking on the strip. Any time I entered a casino that was air conditioned around 70 degrees, as soon as I walked a couple hundred feet my barometer changed and adjusted my elevation to crazy levels. My elevation only changed maybe 10 feet, so I had to take my watch out of auto mode and set it to barometer mode to maintain correct elevation readings.

0 Gregor K. over 5 years ago in reply to Former Member

Hey. Auto mode

0 Former Member over 5 years ago in reply to Former Member

No, I read you were using auto mode and that's what I'm referring too. Your watch has no idea if you just ran on a hill slope or if a gust wind hit you. It does nothing more than guesses when in auto mode as to what made the barometer change. Sometimes it's right, sometimes wrong and sometimes it's way off.

So you recommend to use altimeter mode? Are you using that on 945?

Why does garmin enable auto mode? They could do this as follows: automatically change the watch mode to an altimeter for a specific activity such as bike, walking, running ... and for other activities change watch mode to barometric mode. And they wouldn't have to bother with the automatic mode.

0 Former Member over 5 years ago in reply to Former Member

Yes, I use a 945.

Why does garmin enable auto mode?

I leave my watch in auto mode the majority of the time. Most of the time it works quite well. Depending on the activity and the conditions, there are times I'll change the modes. Most people aren't outside for awhile prior to starting their activity where the watch has had time to adjust to the change in pressure and temperature. That's why I said it's important to note the pressure readings before, during and after the activity so these changes in elevation can be recognized. I'm sure you've read many of the "I went on a run today, and my start and stop points had different elevations even though they were both the same spot" threads. How many left a build or vehicle and then started their run soon after? Did the watch already adjust to the new temperature or pressure change. Did the wind pick up or start gusting? I'll ask what their barometer read before, during and after their run and they'll have no idea nor wonder why it was important to do so. Next time you do a test activity, pay particular attention to the readings. Outside of a defective watch, you'll notice it does make sense what's going on.

0 Former Member over 5 years ago

UPDATE #8

I did exchange 5 emails with [email protected]. Because I dont live in Englad they said that I should contact my local garmin support in my country, they did send me a contact, which I did already know.

I did prepare document with description of problem. But before that I did try to phone them. My 3th attempt was successful and answer was:

1) accuracy of barometric altimeter is cca 20m

2) I have to calibrate altimeter before each ride

3) I have to use only altimeter watch mode (he said that I have to decide depend on activity, but for MTB in hills I have to use altimeter). His argument was that the weather is not changing so fast so assumption is that during the activity will be almost the same pressure. I did think about that and I did try to find how fast can pressure change (exclude situation that storm is coming). I did not find anything so I did check national weather station report. They have 7 day chart and max drop was cca 0.6hPa per hour. Lets say that pressure can drop 1hPa per hour, that means 10m diff. I think that I can accept that.

Conclusion: I decide that I will try my MTB ride with watch mode = altimeter.

@TMK17 mentioned that before activity we should be outside for awhile. Usually I am outside cca 10minutes out before I start to ride bike, checking bike, puting shoes on ... (garage is open) AND when I am cca 500m away from home I am starting activity. I am lucky, because in that distance from home I have tourist guide post with altitude information so I can calibrate altimeter. Maybe I will extend those 10minutes.

If problem remain, then I will send watch to garmin.

0 super6uno over 5 years ago

Yesterday I bought a Garmin Forerunner 945 and the sensor is also in the back, but the result after two activities, sweating a lot, has been perfect. In a cardio activity in the Gym the altimeter has not moved anything, in the instinct it was a roller coaster.

So I think it must be a hardware problem, and not the sensor position.