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Altitude Calculation Principle: Barometric altimeters work on the principle that atmospheric pressure decreases with increasing altitude. They have a built-in barometric sensor that measures the air pressure at your current location. By comparing this pressure reading to a reference pressure (usually a standard pressure at sea level), the altimeter calculates your current altitude.
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Pressure Changes with Weather: Weather conditions, including changes in humidity and air pressure, can significantly affect the atmospheric pressure at any given location. For example, when a low-pressure system (associated with stormy/rainy weather or humidity) moves into an area, the atmospheric pressure decreases. Conversely, high-pressure systems (associated with clear and dry weather) have higher atmospheric pressure.
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Impact on Altitude Reading: Any fluctuations in atmospheric pressure due to weather changes can lead to inaccuracies in the altitude reading of a barometric altimeter. For instance, if the atmospheric pressure suddenly drops because of an approaching storm, the altimeter may erroneously indicate that you have ascended in altitude even if you have not moved. This same concept is present when there is more humidity present in the air at the beginning of a run or activity; the reading at the beginning of the activity will be higher than it actually is due to the humidity, and as it moves out of the area the true elevation will be present, which could result in a net-downhill out-and-back elevation profile, as seen below. This elevation profile is from a traditional out-and-back run from an environment where the humidity was very high at the beginning of the run, and then moved out of the area as the run progressed.
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Calibration: To maintain accuracy, barometric altimeters often need to be calibrated regularly. Changes in weather, humidity, and altitude can cause the altimeter to drift from its calibrated settings, leading to less accurate altitude readings.
In summary, GPS devices with barometric altimeters are affected by changes in humidity and air pressure because their altitude measurements are based on atmospheric pressure. Weather-related fluctuations in pressure can lead to inaccuracies in altitude readings, and regular calibration is necessary to maintain accuracy. Combining barometric and GPS data taken from calibration steps can help improve altitude accuracy in these devices.
It is recommended to calibrate the elevation during daily tracking via GPS or manually input on a regular basis. COROS devices automatically calibrate the elevation using GPS during outdoor workouts to ensure the best accuracy.
Please follow the step below to calibrate the elevation on your watch:
- Main watch face → System → Sensors → Calibration → Elevation → Use GPS, or Enter Elevation.
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Make sure to stand in an open field when calibrating the elevation using GPS for the best accuracy.
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Please follow the step below to calibrate the elevation on DURA:
- Main menu → System → More Settings → Calibration → Elevation → Use GPS, or Enter Elevation.
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Make sure to stand in an open field when calibrating the elevation using GPS for the best accuracy.
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