# 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](https://gml.noaa.gov/grad/solcalc/) 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](https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml)). * **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 {% embed url="" %}