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Aligning Wind Direction to True North vs. Magnetic North

How to Reset Magnetic Declination on the Magellan Weather Station

The compass in the Magellan Weather Station all-in-one sensor is aligned to Magnetic North. At the factory, the declination angle is set to correct wind direction output to True North based on the "Ship To" address. Once the declination angle is set in the sensor, it is stored permanently in non-volatile memory.

The declination angle needs to be reset only if the system is moved to a significantly different geographic location or if wind direction alignment to magnetic north is desired. Users can input the magnetic declination angle of any given geographic location using a terminal program such as HyperTerminal or Putty.

Magellan Weather Station

To Reset the Magnetic Declination

1. Determine the Correct Declination

The following web site may be helpful in determining the correct declination for your site:

Enter your zip code and click "Get Location" OR manually enter latitude and longitude.

Click "Compute Declination".

The declination will be displayed in degrees (º) and minutes ('), e.g. 16º 27'. Divide the minutes by 60 to get decimal remainder of degrees, e.g. 27 minutes = 0.45 degrees. The declination will be rounded up from 16.45 to 16.5 to conform to the data entry format of one decimal place.

2. Read or Set the Magnetic Declination

With the Magellan sensor connected through the Interface Module to a computer, start HyperTerminal program. (This program can be accessed through the Windows Start button - All Programs - Accessories - Communications.) The automatic weather data output should start streaming.

Activate Terminal mode by pressing the Enter button three times in quick succession (within a 2-second period). You should receive the following prompt: Command (HE for Help, QU to Quit):

Use the MD command as shown below.

To Read or Set the magnetic declination:




Report current Magnetic Declination


Set declination to xx.x degrees

Note: West declination values are entered and reported as negative values.


In the example above, the declination is 16° 27'. The value converted to decimal is 16.45. If entered as such, it will be rounded up to 16.5.

Enter the following commands:


QU[Enter] to quit.

Y[Enter] to save.

Magnetic Declination


by Columbia Weather Systems