We describe a method for differential correction of ionospheric delay of GNSS signals in single-frequency measurements. The method involves refining the ionospheric error in measuring pseudoranges for remote receivers, using data obtained by a reference receiver. For specific locations of a receiver and ionospheric pierce points of NS signal propagation paths to it, in the epignosis mode we assess the effectiveness of the method considered. We set the critical frequency data to adjust the ionospheric model for the current situation, using vertical sounding data.
The paper addresses the problem of filtering the phase noise of probing signals, using additional spatial field processing. This field processing relies on the Double Weighted Fourier Transform (DWFT). We have shown it is possible to reconstruct images of plasma irregularities with high resolution, using DWFT spatial processing for circular field measurements under conditions of phase noise of probing signals.
A method of specifying changes in the ionospheric critical frequency along a path has been developed to more accurately estimate the effect of longitudinal horizontal electron density gradients along a path on the accuracy of the calculation of ionospheric delay of GNSS signals. The transition has been made from a linear dependence to a dependence representing a second-order curve through quadratic spline interpolation. To exemplify differences between the real form of change in the critical frequency along a path and its linear representation, we assess the effect of these differences on the accuracy of the calculation of ionospheric delay. Specifying the form of horizontal gradients of the critical frequency closest to the real one is shown to be quite important.
Through numerical simulation, we have assessed the effect of longitudinal horizontal electron density gradients along the transionospheric propagation path on ionospheric delay of GNSS signals. We have found that in some cases their consideration may result in a significant refinement of the value of ionospheric delay of GNSS signals, which can be as large as several tens of percent compared to that in the absence of these gradients. We have shown that the method of determining slant TEC through direct signal-path integration in the ionospheric model with due regard for such gradients may somewhat improve the accuracy of positioning performed in single-frequency GNSS measurements.
We have refined values of critical frequencies, obtained from the IRI model, for a given hour at certain space points adjacent to the site for which vertical ionospheric sounding data are available. The refinement is based on data on the difference between ionospheric delays of signals received from two navigation satellites at one point in time. As reference values we have used the differences calculated from the ionospheric total electron content, obtained from IONEX maps. As derived from data for 20 pairs of satellites, the mean value of the relative difference between the refined critical frequency and the estimated one is 9.8 %.
Critical frequencies specified by the IRI model are determined for a given hour at two closely adjacent space points. A correction parameter is differences between pseudo-distances of signals from a pair of navigation satellites, recorded by a single-frequency receiver. We compare the differences calculated from measurements of the total electron content at frequency correction points and from the model with fitting of critical frequencies at these points. It is shown that in most cases the similarity between model and experimental values of the pseudo-distances difference exists when critical frequency variations do not exceed 30%.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.