Broadcast range
The local terrain can also play a major role in limiting broadcast range. Mountain ranges block FM broadcasts, AM broadcasts, and TV broadcasts, and other signals in the VHF and especially UHF ranges, respectively. This terrain shielding occurs when the line of sight is blocked by something through which the radio waves cannot pass, particularly stone. At times this may be moot due to weather, such as when the tall cumulonimbus clouds of a squall line of thunderstorms reflect the signal over the top, like an extremely tall radio tower. Conversely, heavy rain may attenuate the range of even local stations. ATSC digital television is affected by wind and trees (even if not surrounding the transmitter or receiver locations), apparently related to its use of 8VSB modulation instead of COFDM.
Error analysis for the Global Positioning System
Space weather degrades GPS operation in two ways, direct interference by solar radio burst noise in the same frequency band or by scattering of the GPS radio signal in ionospheric irregularities referred to as scintillation. Both forms of degradation follow the 11 year solar cycle and are a maximum at sunspot maximum although they can occur at any time. Solar radio bursts are associated with solar flares and coronal mass ejections (CMEs) and their impact can affect reception over the half of the Earth facing the sun. Scintillation occurs most frequently at tropical latitudes where it is a night time phenomenon. It occurs less frequently at high latitudes or mid-latitudes where magnetic storms can lead to scintillation. In addition to producing scintillation, magnetic storms can produce strong ionospheric gradients that degrade the accuracy of SBAS systems.