Studies of storm-enhanced density impact on DGPS using IGS reference station data

DGPS services are provided in support of land and marine applications by many government agencies worldwide. Horizontal positioning accuracies in the order of several metres are typically achieved for these systems. Under high levels of ionospheric activity, however, significant degradations in DGPS positioning accuracies can occur. In particular, gradients of up to 50 ppm are associated with a feature known as storm-enhanced density (SED). This feature is a localized enhancement of total electron content (TEC) extending north through the mid-latitudes into the polar region. DGPS positioning errors of 20 m or more can persist for hours during such events. In this paper, archived IGS data from GPS reference stations are used to derive high-resolution TEC maps for two SED events. The impact of SED effects on DGPS horizontal positioning accuracies is then quantified using data from select IGS reference stations in North America and Europe. Results indicate that positioning accuracies may be degraded by factors as large as 10–20 during such events.