Campbell Scientific ET107 Evapotranspiration Monitoring Station - Manual (Page 17)

ET107 Weather Station
Declination angles east of True North are considered negative, and are subtracted
from 0 degrees to get True North as shown FIGURE 1-7. Declination angles west
of True North are considered positive, and are added to 0 degrees to get True
North as shown in FIGURE 1-8. For example, the declination for Logan, Utah is
12.4° East. True North is 360° – 12.4°, or 347.6° as read on a compass.
* Other methods employ observations using the North Star or the sun, and
are discussed in the Quality Assurance Handbook for Air Pollution
Measurement Systems, Volume IV - Meteorological Measurements 4 .
FIGURE 1-6. Magnetic declination for the contiguous United States
(2004)
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