I was looking at Garmin's product support page for the 935. While reading about elevation, the website explained the "auto", "altimeter" and "barometer" mode settings in quite detail. In the section about calibrating the altimeter it reads "From here you can choose Calibrate to calibrate the sensor using a current known elevation or by using the GPS elevation reading, or toggle the Auto Calibrate setting on or off." Calibrating it manually with a known elevation or using GPS are self explanatory, but I can't find any info on auto calibration. Would anyone be able to explain what the auto calibration "on" does and how it does it? Secondly, why is there an option to turn it off? Is there a situation where one would want it on as opposed to off or vise versa? Any help with this would be appreciated.
Yes, that is very likely (and I already mentioned that in another thread). But any larger error caused by temperature would render the measurements useless unless compensated in software.
So I am pretty confident that the pressure sensor is either intended to be adequately insensible to temperature changes, or its output is corrected in software before being used for anything. In either case, you should not see any significant altimeter error from a temperature change.
I read previously that temperature compensation was the main purpose of the internal thermometer. Could it be that it is not always at the same temperature as the pressure sensor so errors result e.g. due to hardware placement limitations?
Perhaps. In this case I assume that we would see the error disappearing when the watch has been at the same temperature for some time so all parts of the watch has the same temperature. But I am only guessing here. There could also be a temperature dependency which is not equal between copies of the watch. Or perhaps a too simple correction function.
When I first got my fenix 3 I was curious about the thermometer readings and put the watch in the fridge and tested it over a few hours, looking occasionally. With many of the measurements there was a difference between the watch and two thermometers I used to check it. I assumed it was the processor heating the thermometer as the fenix 3 was quick to heat up but slow to cool down. I suspect that the internal parts of the watch are very rarely all at the same temperature.
