Altitud correcta barómetro incorrecto

Supongo que cuando se calibra el altímetro el reloj coge la ubicación y el dato barométrico (QNH) de internet hay algún error donde no se translada el dato real del QNH

(I suppose that when the altimeter is calibrated the clock takes the location and the barometric data (QNH) of the internet there is some error where the real data of the QNH is not transferred.)

I do not know what Garmin device you own, but on my Garmin Instinct, when I calibrate the barometer, then first of all it acquires the elevation (manually, from GPS, or from the DEM topographic database), and then I have to enter manually the current sea-level-based barometric pressure. In that way, the accuracy of the barometric reading is established. I may be wrong, but I doubt that any Garmin model reads the atmospheric pressure for the calibration purpose from any online sources automatically.

Please note, that the manual entry of the sea-level pressure is accessible only when you calibrate the barometer, not the altimeter! And it is also unnecessary. Unlike the calibration of the altimeter, that should be done frequently, the calibrating of the barometer, with the manual entry of the pressure, is needed ony rarely - just when it starts showing incorrect values like in your case. Once done, the pressure adjusts to the correct value automatically when you calibrate the altimeter (without entering the pressure data anymore). It may only need a recalibration, if the sensor starts reporting wrong values due to aging, or dirt (you better wash it in the later case, first).

Gracias por su respuesta, mi dispositivo es vivoactive 3 el proceso de calibración del altímetro/barómetro según garmin es un proceso automático, no hay posibilidad de introducir ningún dato para el proceso de calibración. Descarto que el sensor este defectuoso por suciedad, los datos de altitud son mas o menos correctos, donde hay mucha diferencia es en el dato barométrico QNH, hay una diferencia de 10 mb.

mi dispositivo es vivoactive

Yes, that's correct, Vivoactive 3 does not have any option of manual calibration of the altimeter or barometer. It can only calibrate the altimeter with the help of GPS acquired elevation. The accuracy of GPS elevation is in the range of tens of meters, hence it can easily make for the difference of some 10mb, even if the barometer were 100% perfectly factory-calibrated.

So it looks like you are out of luck, and cannot get it much better. Perhpas it may get better later this year with the completion of the Galileo satellite fleet, and the improved accuracy of the navigation system. Theoretically the vertical accuracy of the Galileo navigation system will be 8m at dual-frequecy receivers, though I am not sure whether Vivoactive 3 has one. If not, then the theoretical vertical accuracy of single frenquency receivers is 35m, which is still better than with GPS. You would need to turn on the option GPS+Galileo in the GPS settings.