Ionospheric modelling in support of single station location of long range transmitters

Abstract Position estimates derived from a large data base of bearing and elevation angles of signals from distant HF transmitters have been analysed, with a view to comparing the validity of available ionospheric models and to examining ionospheric limitations to the accuracy of single station location of such transmitters. In general, the accuracy of the position estimates is almost entirely controlled by a limited ability to model in sufficiently accurate detail the ionospheric effects on the signal propagation. Median miss distances for those cases with a reliable identification of the propagation mode were about 7% for both E and F 2 propagation for all models considered. Difficulties were encountered with the International Reference Ionosphere, which failed to support the observed propagation in half the F 2 propagation cases. Standard deviations of the bearing errors were about 0.5° for E modes and 0.7° for F 2 modes and were largely attributable to the effects of the ionosphere and not to instrumental errors