Assessing the GPS-based slant total electron content (sTEC) accuracy

BRUNINI CLAUDIO; AZPILICUETA FRANCISCO

Montreal, Canadá

Congreso; 37th COSPAR Scientific Assembly; 2008

Committe on Space Research

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-GB;} p.MsoFooter, li.MsoFooter, div.MsoFooter {margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; tab-stops:center 220.95pt right 441.9pt; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-GB;} p.MsoBodyText, li.MsoBodyText, div.MsoBodyText {margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; mso-bidi-font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-ansi-language:ES-TRAD;} @page Section1 {size:21.0cm 842.0pt; margin:70.9pt 70.9pt 70.9pt 70.9pt; mso-header-margin:35.45pt; mso-footer-margin:35.45pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> The main scope of this contribution is to assess the accuracy that can be achieved in the slant total electron content (sTEC) estimated from dual-frequency GPS observations, which depends, primarily, on the calibration of the inter-frequency biases (IFB). Two different calibration approaches are analysed: the so-called satellite-by-satellite, which involves the reduction of the carrier-phase ambiguities effects by levelling the carrier-phase to the code-delay GPS observations and then the estimation of satellite-dependent IFB; and the so-called arc-by-arc, which avoid the use of code-delay observations but requires the estimation of arc-dependent IFB. In principle, the first approach should produce more reliable results because it requires the estimation of les parameters than the second one, but the second approach presents the benefit of being not affected by the levelling error effects that are caused by the presence of the code-delay multi-path.   This contribution discusses two different experiments specifically designed to asses the GPS-based sTEC accuracy: the so-called co-location and synthetic data experiments. The first one is based on the comparison of the calibrated sTEC estimated from the data collected by two nearby GPS receivers, while the second one is based on the use of a synthetic dataset free of calibration errors generated with an empirical ionospheric model. While the co-location experiment is sensitive to the levelling but not to the model error effects, the synthetic data experiment provides a way to assess the calibration biases errors caused by the inconsistencies of the ionospheric model involved in the estimation process.   Both experiments used in a complementary way allowed the estimation of calibration errors of several TECu (total electron content unities) depending on the station location (low, mid or high latitude); the ionospheric conditions (solar and geomagnetic activity, season); characteristics of the GPS instruments (receivers and antennas); and environmental conditions (multi-path). From these results, it could be concluded that the arc-by-arc calibration technique performs better than the satellite-by-satellite one for mid-latitudes while the opposite happens for low-latitudes.   Besides, the technique to crate synthetic dataset presented in this contribution, whose truthfulness is evaluated by comparing the synthetic sTEC and its rate of change (RoT) to the corresponding values obtained from experimental (GPS-based) data, could be a valuable tool for error assessment and model validation.