First results of tilts angles measurements obtained from a vertical sounder

Radiowave propagation in the HF band is subject to path deviations caused by ionospheric tilts. This point is of interest in the direction finding domain, particularly in single site location (SSL). Tilt effects introduce angle of arrival estimation errors, in addition to experimental errors, in particular on azimuth angles. Vertical sounding appears as a technique to study this phenomenon. Such measurements have been implemented by McNamara [1991]; large and small scale tilts can be studied in this way. A method of tilt correction for SSL could use tilt characteristic measurements obtained from a sounder, together with the estimated angles of arrival from the direction finder. The aim of this paper is to present a measurement system and a technique to obtain tilt parameters. In a first part, the link geometry and tilt characteristics are defined. We present the measurement system and the data processing. To compare with measurements, an original procedure to simulate and to predict tilt parameters is described. Finally, experimental and simulated data are shown.