Geoscience Reference
In-Depth Information
fIGURe 9.4
Atmospheric effects on Global Positioning System (GPS) signal propagation.
ISES Solar Cycle Sunspot Number Progression
Data hrough 31 Jan. 08
175
150
125
100
75
50
25
0
Smoothed Monthly Values
Monthly Values
Predicted Values (Smoothed)
Updated 2008 Feb. 6
NOAA/SWPC Boulder, CO USA
fIGURe 9.5
The progression of Solar Cycle 23 (www.sec.noaa.gov/SolarCycle).
it is accomplished by using empirical models of the tropospheric delay (Hofman-Wellenhof et al.,
2001). The total effect in the zenith direction reaches ~2.5 m and increases with the cosecant of the
elevation angle up to ~25 m at a 5° elevation angle. The tropospheric delay consists of the dry com-
ponent (about 90 percent of the total tropospheric refraction), proportional to the density of the gas
