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The Elevation Reading on My Forerunner 745 Is Wrong
The elevation reading you see comes from a barometric altimeter sensor inside the watch. This sensor detects barometric pressure changes in order to determine current elevation at a given point. If you believe the elevation reading from your watch is incorrect, review the following information to help troubleshoot and fix the problem.
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Weather Changes Can Affect Sensor Accuracy
Weather can contribute to an incorrect reading. This includes:
An incoming or departing Low or High pressure system.
This can cause your starting elevation reading to be too high or low. You should manually calibrate to a known elevation in this case. The elevation gain/loss during the recorded activity is typically not affected.
A windy day.
Wind can affect the sensor causing an inaccurate reading. If you are going to record an activity outdoors when it is windy we suggest wearing the sleeve of a shirt or coat over the watch.
Calibrate the Sensor
With proper calibration the watch can achieve an accuracy of +/-10 feet at any given point. Use the information below to determine which calibration options are best for you.
Manually Calibrate the Sensor
Make sure you are outside with a clear open view of the sky around you.
Press and hold the Up button to enter the Main Menu.
Press the down button 8 times and select Sensors & Accessories.
Select Altimeter.
Select Calibrate.
Select an option:
Enter current elevation? (Yes): Use this option to calibrate if you know the current elevation. This option offers the most accurate calibration.
Use GPS: This mode will determine your elevation through GPS triangulation. Elevation calibrated through GPS is accurate to +/-400 feet at any given point and is the least accurate.
Automatically Calibrate the Sensor
Make sure you are outside with a clear open view of the sky around you.
Press and hold the Up button to enter the Main Menu.
Press the down button 8 times and select Sensors & Accessories > Auto Cal.
On - The watch will calibrate the altimeter anytime a GPS signal is acquired.
Nightly - Setting auto calibration to Nightly will only calibrate the altimeter once every night during your sleep window set in your Garmin Connect™ account. If paired, the Garmin Connect™ app uses location data from the phone and compares it to the DEM information of the watch. This allows the nightly calibration feature to work better but is not required.
When starting an activity, the watch will show current calibration and give the options to accept or recalibrate.
Nightly calibration is also performed when auto calibration is set to On.