Campbell IRGASON, Product Manual

Page: 48 / 91

The program default of 0 for sonic_azimuth is used only if a site-specific value has not been
entered using the keyboard or through
LoggerNet .
FIGURE 10-1 (p. 44) and FIGURE 10-2 (p. 45) show the compass and sonic coordinate system. Both
figures show the sonic’s negative x-axis pointing to the west (compass azimuth of 270°). The wind
direction is measured in degrees clockwise from due north. In the compass coordinate system,
the wind direction (WD) is 200. To calculate the wind direction in
FIGURE 10-1 (p. 44), the
orientation of the sonic anemometer relative to due north is needed in the program. FIGURE 10-2
(p. 45) is in a right-handed coordinate system, and the wind vector direction is measured in
degrees counterclockwise from the positive x-axis. Therefore, the wind vector direction (WD_
sonic) is 70°.
FIGURE 10-1. Compass coordinate system, compass wind direction is 200°.
The sonic azimuth of the anemometer is 270°
IRGASON® Integrated CO
2
/H
2
O Open-Path Gas Analyzer and 3D Sonic Anemometer 44