@elo.egypte
In that case you cannot fix the issue.
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I just came across this old thread …
I don’t know if the #ALT# tag is wrong or not, but you can calculate the altitude yourself from the #ATM# tag.
refer:
where P is replaced by #ATM# ( which is in hPa )
and P0 by 1013.25 hPa
Note that the formula assumes that the pressure at sea level is 1013.25 hPa, but this is only sometimes true as high and low pressure weather systems roll through. The error due to weather can be very large, around 100m per 12 hPa of pressure change. Low pressure systems will result in higher than true altitude and the opposite for high pressure systems.
Still it can be fun to play with and can also still be used to estimate the change in altitude as you climb a hill for instance. Take note of the altitude on your watch when you start and subtract that from the value at the top of the hill and the difference will be pretty close to the height of the climb.
If you have access to VARs then you can also amend the expression above to correct the #ATM# value by the offset from standard pressure due to weather.
ie. replace P with (#ATM#+#VAR_1#)
where #VAR_1# represents the change in pressure due to weather
ie. set #VAR_1# to round (1013.25-{actual sea level pressure from a near weather station })
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