Campbell TGT1, Operator'S Manual

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G-1
Appendix G. Local Magnetic
Declination
G.1 Determining True North
Orientation of the antenna is done after the location of True North has been
found.
1. Establish a reference point on the horizon for True North (or other
direction relative to True North). True North is usually found by reading a
magnetic compass and applying the correction for magnetic declination as
discussed below. 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
.
A general map showing magnetic declination for the contiguous United States
is shown in Figure G-1. Magnetic declination for a specific site can be
obtained from a USGS map, local airport, or through a computer service
offered by the USGS called GEOMAG (recommended). Section G.2 has a
listing of the prompts and the declination determined by GEOMAG for a site
near Logan, Utah.
Declination angles east of True North are considered negative, and are subtracted
from 0 degrees to get True North as shown in Figure G-2. Declination angles
west of True North are considered positive, and are added to 0 degrees to get
True North as shown in Figure G-3.
Subtract declination from 360
°
Add declination to 0
°
22 E
18 E
16 E
14 E
12 E
10 E
8 E
6 E
4 E
2 E
0
2 W
4 W
6 W
8 W
10 W
14 W
12 W
16 W
18 W
20 W
20 E
FIGURE G-1. Magnetic Declination for the Contiguous United States