Magnetic vs. True North: Adjusting for Declination
What’s up with Magnetic North vs True North?
“True north” is the northern axis of rotation of the Earth. It is the point where the lines of longitude converge on maps. “Magnetic north” is the point on the Earth’s surface where its magnetic field points directly downwards.
Magnetic north does not exactly coincide with true north, and its location changes over time. The difference between Magnetic North and True North is called “Declination” or “Variation”.
The Kestrel 4500, just like any other compass, will measure Magnetic North. However, True North can be displayed by simply programming the Variation for your location. When viewing the Direction in Magnetic North mode, the display will show “Magnetic North” below the reading. When viewing the Direction in True North mode, the display will show “True N #.# E”, where #.# is the variation setting.
Kestrel 4500: To switch between these modes, press the (–) button. Then use the < and > buttons to toggle between Magnetic and True. To enter the variation for your location, press down to highlight Variation, then < and > to adjust the value.
Kestrel 5500: On the Direction screen, hit the middle button to settings and with 'mode' highlighted, use your left/right arrows to toggle from Magnetic to True. To enter the variation for your location, press down to highlight Variation, then < and > to adjust the value.
How to Enter the Variation/Declination
These values for your location can be obtained on the internet. The NOAA website is an excellent resource for this information: www.ngdc.noaa.gov
To find your Variation value in the United States by zip code, go the NOAA Compute Your Declination page