Total mileage 23% different reported. - Amazfit

Hi everone,
I am using Amazfit Stratos, Rom version 2.3.4.0 .I have a climbing activity on 1 spetember 2018.
The total mileage shown on watch & Amazfit App is 15.1km, but it only 12.2km (12.6km if consider 3d distance) via Strava or Google Earth after I download the gpx file, it is 23% different. The huge mileage different also happened when climbing mountain with elevation more than 500m, the others activity will have 3% to 6% different (the watch reported higher).
Anyone have this problem? How to solve it?
Is anyone noted that the elevation info always missing in the first few point of the GPX file downloaded?

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Probably you had 3D Data on (search for what it means).

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lfom said:
Probably you had 3D Data on (search for what it means).
Click to expand...
Click to collapse
Yes, I know what is 3d data, I have set 3d data on for this climbing activity.
But it is 12.2km (without consider 3d) and 12.6km (with consider 3d), calculated by myself and checked using "Google Earth".
Will it because of movement of the hand where I wear the watch?

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Sounds like a problem with the altitude measurement. I'm not happy with that too. Opening compass, doubletapping on it and waiting for a GPS fix before starting an activity is helping a bit.
I see several reasons for this:
1) The phone app is smoothing out the altitude data by using digital elevation map data, which at the end comes to different mileages.
2) In the mountains unprecise GPS signal can lead to significant differences, 30m 2D can sum up to 100m or more 3D, a balance between weak signal filtering and loosing signal is not easy to achieve.
3) During my tours I had another GPS running parallel. What made a real difference was, what I wrote under 2) and that my Pace did not exactly recognize pauses, which resulted in several pausing clusters which added to the mileage.
My conclusion:
I'm using the watch but after the activity I:
1) export it to tcx format via the exporter available in this forum.
2) manually delete the first trackpoints which either have no altititude or an unrealistic speed.
3) correct the altitude with external tools if I see it necessary.
Some of this after activity steps are done by the phone app automatically. Since the phone app is not giving me options for this I use other tool to know exactly what is going on.
Edit: The handmovement shouldn't influence outdoor results.

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Did you check the altitude graph? It seems that run/walk use GPS for altitude whereas trail run/climb use the barometer. I still think it's related to 3D Data: the higher the altitude change, the higher will be the final difference in distance when compared to common "2D" data.
---------- Post added at 01:39 PM ---------- Previous post was at 01:24 PM ----------
Also, latest international firmware for Stratos is 2.3.6.1, and you are still running 2.3.4.0... Latest Amasfit app version may make a difference too... Auto-pause may make a difference too: either disable or use something other than "stand still".

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lfom said:
Auto-pause may make a difference too: either disable or use something other than "stand still".
Click to expand...
Click to collapse
Are there other settings for Auto-pause than "on/off"? If so, where can I find them on the pace?
Profil Climbing and profil Trail Running have only Auto-pause "on/off" on ROM Pacificator WOS 2.6.3.1.

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nhedgehog said:
Are there other settings for Auto-pause than "on/off"? If so, where can I find them on the pace?
Profil Climbing and profil Trail Running have only Auto-pause "on/off" on ROM Pacificator WOS 2.6.3.1.
Click to expand...
Click to collapse
Not all activities have the other options, then you can try disabling it and use the button to pause manually. When recording walkings I found that it was too sensitive and it added a lot of bad data points to GPS when enabled.

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lfom said:
Not all activities have the other options, then you can try disabling it and use the button to pause manually. When recording walkings I found that it was too sensitive and it added a lot of bad data points to GPS when enabled.
Click to expand...
Click to collapse
I experienced the same phenomena. Thats why I stopped using "Auto-pause" and was wondering now about the possibility of finetuning autopause. Which activities have this, I couldn't find any?
Edit:
I found one: Cycling (1km/h steps)
Thats understandable but with the bad HDOP&VDOP filtering the Pace has, configurable Autopause in 0.1km/h steps could help in other activities too.

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nhedgehog said:
I experienced the same phenomena. Thats why I stopped using "Auto-pause" and was wondering now about the possibility of finetuning autopause. Which activities have this, I couldn't find any?
Click to expand...
Click to collapse
Run has an settings based on pace, Outdoor cycling has it based on speed. "Common" walk doesn't have it, it's either on or off.

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[/COLOR]Also, latest international firmware for Stratos is 2.3.6.1, and you are still running 2.3.4.0... Latest Amasfit app version may make a difference too... Auto-pause may make a difference too: either disable or use something other than "stand still".[/QUOTE]
the firmware now is 2.3.6.1 (2.3.4.0 is when that particular climbing activity on 1 september ),
I always off the 'Auto pause' except the first time i use the watch, because it keep on pausing (because my activity is inside the forest).
https://drive.google.com/open?id=1KSCwCRNmbnLdRgJaI1x9lkoogJN0Qv25
this is the list of all my activity, it is true that '3d data' will affect the total mileage. When I on '3d data' to climb the mountain, the total mileage is 20+% higher, but it is 3 to 5% higher when only the small hill.
However, activity after 29 september , '3d data' is set to 'off', the total mileage still 3 to 5 % higher.
lfom said:
Did you check the altitude graph? It seems that run/walk use GPS for altitude whereas trail run/climb use the barometer. I still think it's related to 3D Data: the higher the altitude change, the higher will be the final difference in distance when compared to common "2D" data.
https://drive.google.com/open?id=10whj9izJoNCdXGQOxWMZ-pvTdYv2fW5e
https://drive.google.com/open?id=1PjBOYg-Op3nOSbuGoq2i7gDrRceBq7On
https://drive.google.com/open?id=1T-pJWxehu0a7TpqhL1-7S3Is7GkLR5eb
https://drive.google.com/open?id=1PXFCi2TMMsf94Kt5GxrWCkF-J_3S8JQp
those are the elevation profile of activity on '1/9 climb 3d-on', '3/11 walk 3d-off', '10/11 run 3d-off' & '17/11 trail run 3d-off', it seem that all altitude record by Amazfit is lower than which corrected by 'Strava' or ' gpsvisualizer.com' or record by handphone.
Any solution to keep the total mileage within 1 to 2%? after off the 'auto pause' & '3d data' ? 3 to 5% is still consider too high.
Click to expand...
Click to collapse

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Having a look at your pictures your altitude data is much better than that what my pace produces before this was "corrected" by the phone app.
I guess that means it comes from the phone app.
So that leaves us 3 options:
1)
Those 3 altitude correcting sources you use:
Amazfit
Strava
GPS visualizer
are probably using different altitude maps - meaning you can't compare them and have to decide which one you use. I guess the one from amazfit
has a lower resolution compared to those from Strava&GPS visualizer. You probably can't change the altitude mapsource of those 3 apps - just decide which one you prefer and stick to it.
2)
If I'm using altitude correction I don't rely on either of those apps but use LIDAR maps which have a higher resolution and therefore representing the altitude of the area better:
http://data.opendataportal.at/dataset/dtm-germany
To do that I need the RAW data from the watch, which I get as mentioned via a python script as tcx files directly from the watch. Edit: One could use the gpx file which the watch procides under activities but the program I use for reprocessing the track does not recognize the included heartrate data. Otherwise internal created gpx and external created tcx don't differ much.
My resolution: another app
3)
The third option I see would be relying on the altitude data the watch provides, which I personaly found not reliable at all. I guess that has something to do with the filtering of weak signal from the gps chip, which is done by the gps firmware. To solve this problem we can only hope for some better filtering via GPS firmware by the manufacturer.