Wind Vane - Alignment

Accurate wind vane alignment to true north (geographic north) is critical for reliable meteorological and wind turbine data. Misalignment introduces errors in wind direction measurements.

Option 1: Aligning to True North with a Solar Noon Shadow

Use the NOAA Solar Calculator tool to determine solar noon for your location (in coordinates) at the current date and time. Then follow the slideshow below and use the alignment cap to determine true north.

Option 2: Aligning with a Compass and Magnetic Declination

If you use a compass to align your wind vane, remember that a compass points to magnetic north, not true (geographic) north. The difference between these directions is called magnetic declination, which varies by location and changes over time. To ensure accurate alignment:

• Find your local magnetic declination (NOAA provides an online calculator).

• Adjust your compass reading:

  • If your declination is east (positive), subtract the declination value from your compass bearing.

  • If your declination is west (negative), add the declination value to your compass bearing.

• Set the wind vane so it points to the adjusted bearing for true north, not the uncorrected compass north.

For example, if your magnetic declination is 10° east, and your compass points to 0° (magnetic north), align the wind vane to 350° (0° – 10°) to achieve true north. If your declination is 10° west, align to 10° (0° + 10°).

Solar Noon Instruction Slides