> For the complete documentation index, see [llms.txt](https://3dpaws.comet.ucar.edu/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://3dpaws.comet.ucar.edu/deploying-3d-paws/wind-vane-alignment.md).

# 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="<https://docs.google.com/presentation/d/1BeCbO4roiUy_lj_0uDC8EfB9S0nw7K6W/edit?ouid=102244773211795243299&rtpof=true&sd=true&usp=sharing>" %}


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