La Crosse Technology WTK27 Bedienungsanleitung Seite 21

When finished, LCD will display "OK" if the calibration is successful or display

"Fail" if it is failed as below.
(2) Set the Declination Angle
The angle between magnetic north and the true north direction is called magnetic
declination. The earth's magnetic poles fluctuate over time, and it also varies from
place to place. Finding the declination on the map or website, then set the
declination on this unit to offset the difference between magnetic north and true
north. Please note that if you fail to do this, the readings you get from the compass
could be in error.
In COMPASS mode, hold "COMPASS" button for 3 seconds to enter the compass

sensor calibration mode, press "MODE" button to enter setting of declination
angle. The angle would flash on the LCD. (for example, as below, " 0° " will flash
on the LCD)
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EN-9