Can you please help to find the correct elevation gain data?

Hi,

I have the latest version of Locus Map Pro.

I'm still a bit puzzled when it comes to figure out correct elevation gain data. While I know sport watches are not scientific tools and there are many factors in play but maybe I can get a better understanding.

Usually we get suspicious when my Garmin Instinct altimeter gives a much higher result compared to my partner's 735XT which calclulates based on topographic elevation data as far as I know.

So my data is:

Garmin original in Garmin app: 422 m

Garmin with elevation correction in Garmin app: 344 m (about the same as the map based value on the 735XT)

Garmin original exported and loaded to Locus map: 406 m

Garmin with elevation correction exported and loaded to Locus map: 387 m

Locus map own recording based on mobile phone GPS data: 467 m

Since my Locus map has elevation data I managed to check some random points of my hike and the best match was the corrected one (387). The original Garmin barometric values were usually off by -20-30 meters.

So I am kind of lost as to which should be the correct data.

- how come two sets of map based elevation data (Garmin vs Locus) can be so off?

- is map elevation data in Locus based on the app itself or on the map I am using (I have an externally downloaded offline map)?

- as long as my path was recorded correctly, can I expect the map based elevation data to be correct?

I always calibrate elevation on my Garmin when starting and the initial value is correct.

Any comments would be much appreciated.

Thanks.

Ps.: I also randomly checked some known elevation points for the track that was recorded by the phone and those seemed OK (maybe a lucky pick), still it has the highest elevation gain which is not correct most probably.