Garmin G300 Installation Manual page 81

The Magnetometer Calibration Procedure must consistently report "CALIBRATION
SUCCESSFUL / SITE IS CLEAN" in both the clockwise and counter-clockwise
directions for the site to be considered acceptable. More than one failure out of ten
attempts in a given direction would be sufficient reason to conclude the site is not
acceptable.
A site that is used repeatedly to perform the Magnetometer Calibration Procedure should be re-evaluated
every 12 months, and after any significant construction or placement of magnetic objects (above or below
ground) within 50 meters of the location.
G300 Installation Manual – Post Installation Checkout and Calibration Procedures
190-00921-01
NOTE
Page 9-25
Revision A