RAWS-H Remote Automated Weather Station
8.1.2 USGS Web Calculator
The USGS provides an easy way of determining declination of a specific site.
Since magnetic declination fluctuates with time, it should be adjusted each time
the wind sensor orientation is adjusted. The calculator can be accessed at:
www.ngdc.noaa.gov/geomagmodels/Declination.jsp
. Figure 8.1-4 shows an
example for Logan, UT.
FIGURE 8.1-4. USGS Web Calculator
In the example above the declination for Logan, UT is 12º 24
′
or 12.4º. As
shown in Figure 8.1-4, the declination for Utah is East (positive), so True
North for this site is 360 – 12.4 = 347.6 degrees. The annual change is 7
minutes West per year or -7 minutes/year.
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