Section 1. Preparation and Siting
general map showing magnetic declination for the contiguous United States is
shown in Figure 1.5-1.
Declination angles east of True North are considered negative, and are subtracted
from 0 degrees to get True North as shown Figure 1.5-2. Declination angles west
of True North are considered positive, and are added to 0 degrees to get True
North as shown in Figure 1.5-3. For example, the declination for Logan, Utah is
13.80
°
East. True North is 360
°
- 13.80
°
, or 346.2
°
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
.
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 1.5-1. Magnetic Declination for the Contiguous United States
1.5.1 NSSDC CGM Service
The NSSDC CGM (Corrected Geomagnetic) Service provides an easy way of
determining magnetic declination of a specific site. Since magnetic declination
fluctuates with time, it should be determined each time the wind vane
orientation is adjusted. It can be accessed on the world wide web at
http://nssdc.gsfc.nasa.gov/space/cgm/cgm.html
If you know the latitude and longitude of your site, fill out Form 1 for an
accurate magnetic declination. Below is an example for Logan, Utah U.S.A.
If you do not know the latitude and longitude of your site, fill out Form 2 for
estimate of magnetic declination. Note that longitude is expressed in 0 to 360
degrees east of the Greenwich prime meridian, and that north latitudes are
positive.
A table containing similar information to the following will be returned later
submitting Forms 1 or 2.
1-7
Summary of Contents for ET107
Page 8: ...ET107 Weather Station Table of Contents vi This is a blank page...
Page 68: ...Section 3 ET Software 3 2 This is a blank page...
Page 86: ...Section 4 Maintenance Troubleshooting and Schematics 4 18...
Page 101: ...Appendix C Exploded Views C 1 Enclosure C 1...
Page 102: ...Appendix C Exploded Views C 2 Crossarm C 2...
Page 109: ......
