  The investigation of the Earth ionosphere both in a quiet and a disturbed
states is still desirable. Despite recent progress in its modeling and in
estimating the electron concentration along the line of sight by GPS signals,
the impact of the disturbed ionosphere and magnetic field on the wave
propagation still remains not sufficiently understood. This is due to lack of
information on the polarization of GPS signals, and due to poorly conditioned
models of the ionosphere at high altitudes and strong perturbations. In this
article we consider a possibility of using the data of pulsar radio emission,
along with the traditional GPS system data, for the vertical and oblique
sounding of the ionosphere. This approach also allows to monitor parameters of
the propagation medium, such as the dispersion measure and the rotation measure
using changes of the polarization between pulses. By using a selected pulsar
constellation it is possible to increase the number of directions in which
parameters of the ionosphere and the magnetic field can be estimated.
