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 George_Araujo over 2 years ago

I corrected the problem with the barometric altimetry measurement taking care to verify that the device was properly cleaned. After a thorough cleaning with water and detergent, the device re-registered the correct altitude.

0 thomass001 over 2 years ago in reply to bineus

I have sent you a PM.

Regards
Thomas

0 thomass001 over 2 years ago in reply to George_Araujo

George_Araujo said:
I corrected the problem with the barometric altimetry measurement taking care to verify that the device was properly cleaned. After a thorough cleaning with water and detergent, the device re-registered the correct altitude.

Good to hear.

The most of the problems with the elevation measurement is the pressure in the sensor hole because of wind pressure.

You can see it by downhill biking and downhill skiing.

And that's the problem described in this article.

0 Sandra M over 2 years ago in reply to thomass001

Well, that's not exactly my case. I find that on the uphills the reading is much higher than the real one because sweat clogs the barometer (on the downhills I sweat less and the problem is not as pronounced). The profile obtained in uphills is like a saw tooth.

0 4241327 over 2 years ago in reply to Sandra M

In case you are on software version 16.50 (sorry, I didn't read the whole thread), the 'saw tooth' problem you accurately describe has nothing to do with a measurement problem like a clogged altimeter hole, and all with incorrect data interpretation.

This article here is two years old and has little to do with the current problem.

Garmin changed the altimeter / barometer algorithm from 16.00 to 16.50 some weeks ago, and they totally messed it up. This is the same across their complete watch line. They are somehow aware of it, but are not really reacting adequately. Their developers seem to think they can fix the problem by nightly calibration over Garmin cloud. But the problem is their completely changed algorithm, wrong filtering, wrong interpretation of pressure, movement, temperature and time data.

You can downdate to 16.00 via the 16.50 beta, but you will lose all watch settings, so you must back those up via USB and BaseCamp.

Further information can be found here:

forums.garmin.com/.../the-unsatisfactory-altimeter-calibration-change-from-15-00-16-00-to-16-50-shows-that-garmin-should-listen-and-beta-test-more-updated-same-problem-on-fenix-and-epix-2

0 who knows over 2 years ago in reply to 4241327

4241327 said:
But the problem is their completely changed algorithm, wrong filtering, wrong interpretation of pressure, movement, temperature and time data.

I don't believe the problem is with any of the issues you list other than the temperature sensor. I too have an issue with the elevation being off, but not to the extent as others have claimed. I performed a simple test I would appreciate if you could try to see if you have the same results which leads me to believe it's the temperature sensor. I took off my watch which was reading a little high in elevation and set it on my desk. Within a few minutes elevation dropped to the correct level. I left the watch on the desk overnight and the 4 hour graph was flatlined with the correct elevation. I remained at my desk and placed the watch on my wrist. I immediately noticed the watch felt cool. Within a minute, the altimeter started to drop in elevation as it started warming to my skin temperature. That morning I spent a little extra time outdoors warming up before I started my run so the watch could "climatize" before I calibrated. I had no issues following that.

0 Sandra M over 2 years ago in reply to who knows

I don't think the problem is anything other than sweat on the barometer, at least in my case. In fact, since I use the cover that thomass001 kindly sent me I haven't had any more problems with elevation mesure.

0 who knows over 2 years ago in reply to Sandra M

That maybe an additional issue with Instinct owners, but as 4241327 pointed out, the change recently occurred across all Garmin models. My test was performed with a 945 where the barometer port is unaffected by sweat. Even if I where wearing an Instinct, I wasn't perspiring when I placed it back on my wrist. My test had nothing to do with an obstructed barometer port.

0 4241327 over 2 years ago in reply to who knows

I also initially thought it was a problem mainly with the forgotten (!?) temperature calibration, but I don't think that's the case. The dither and drift is much higher than before, even when the watch is constantly on my wrist and I'm inside. There is nothing more I can add. There is a huge discussion about this in the Fenix beta forum, and people have the same problem outside with constant wrist temperature.

Unfortunately, I can't check your assumption anymore, as I have long downdated to 16.00 again - altimeter works like a charm.

0 who knows over 2 years ago in reply to 4241327

I pretty sure any issue I was having on the 945's latest FW was due to sudden temperature changes. I've been outdoors for the past couple hours. Correct elevation of feet 7. Drove into town on an errand and correct elevation of 42 feet. Just got back home and it's back to 7 feet. I'm only having the problem when going from indoors to outdoors and vise versa. Once the watch has become "acclimated" to the new temperature and then calibrated all is good.