Altimeter Auto Calibration for Outdoor Handhelds and Watches

The barometric altimeter sensor found in many outdoor handhelds and watches measures the atmospheric pressure to determine elevation. Below are the possible options for calibrating the altimeter and controlling how elevation data is recorded on the device.

For more information on the accuracy of the altimeter, and GPS elevation accuracy, see Related . 

Calibration Methods

Auto Calibration

The auto calibrate feature eliminates the need to repeatedly calibrate by using the GPS elevation data. This helps eliminate errors caused by changes in weather that alter atmospheric pressure. However, since it relies on GPS elevation, it can be less accurate than manually calibrating to a known elevation. 

Some devices offer a One-Time or Continuous option when using auto calibrate:

• If One-Time is selected, the altimeter will be calibrated by the GPS elevation when an activity is started, but will not be updated after that.

• The Continuous setting provides further calibration throughout the activity to mitigate the effect of changes in pressure over time.

Continuous Calibration

Continuous Calibration uses a combination of GPS, DEM (Digital Elevation Model), and user calibration information.

To reduce fluctuations in elevation during activities, Continuous Calibration takes periodic readings. Generally, the readings should improve as time progresses during the activity, however, auto calibration will not take place when stopped. 

When the device is powered off and back on, it recalibrates to current inputs and takes into account any fluctuations in pressure.

Manual Calibration

Calibration can be done manually, but fluctuations in pressure over time can cause false readings. It is important to periodically calibrate the altimeter to maintain accurate readings.

For information on manually calibrating your altimeter, refer to your owner's manual.

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Additional Altimeter Settings for Handhelds

Barometer Mode

Barometer Mode controls how the device interprets changes in pressure.

• Variable Elevation allows the barometer to measure changes in elevation while you are moving.

• Fixed Elevation assumes the device is stationary at a fixed elevation, so the barometric pressure should only change due to weather.

Pressure Trending

Pressure Trending sets how the device records pressure data.

• Save When Power On only records pressure data while the device is powered on.

• Save Always records all pressure data. This can be helpful when you are watching for pressure fronts, but it will continue to consume battery even when the device is powered off.

Plot Type

Plot Type controls how elevation data is displayed on the Altimeter page. It can be set to record elevation changes over a period of time or distance, barometric pressure over a period of time, or ambient pressure changes over a period of time.