Modern navigational systems that use radio-wave signals reflecting from or propagating through the ionosphere as a means of determining range, or distance, are vulnerable to a variety of effects that can degrade performance. In particular, systems such as the GNSS, that use constellations of earth-orbiting satellites, are affected by space weather phenomena. See Space Weather Effects on GPS. For a map of GNSS receivers see the Canadian Active Control System of Natural Resources Canada.
If the electron density along a signal path from a satellite to a receiver changes very rapidly, as a result of space weather disturbances, the resulting rapid change in the phase of the radio wave may cause difficulties for the GPS receiver, in the form of loss of lock. Temporary loss of lock results in cycle slip, a discontinuity in the phase of the signal. Very rapid variations (less than about 15 seconds) in the signal's strength and phase are known as ionospheric scintillations. Scintillations can be particularly troublesome for receivers that are making carrier-phase measurements and may result in inaccurate or no position information.
Natural Resources Canada collaborates with the CHAIN of the University of New Brunswick to collect information on GNSS scintillations. See the CHAIN Real-time Scintillation Map for current scintillation information. For more information please contact Dr. David Boteler.
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