Methods of inverting high-frequency radar land and sea backscatter to obtain ionospheric vertical profiles offer an important means of remote sensing the ionosphere up to thousands of kilometers from the transmitter/receiver location. This new inversion technique requires the received elevation angle as well as the time delay or group path of the backscattered signal. The technique can be used with both fixed-frequency and swept-frequency radars. The advantage of using swept-frequency radar is that the downrange gradients in electron density can more readily be determined.