Title: VALIDATION OF APPROXIMATION TECHNIQUES FOR LOCAL TOTAL ELECTRON CONTENT MAPPING |
Authors: Krypiak-Gregorczyk Anna, Wielgosz Pawel, Gosciewski Dariusz and Paziewski Jacek |
DOI: 10.13168/AGG.2013.0027 |
Journal: Acta Geodynamica et Geomaterialia, Vol. 10, No. 3 (171), Prague 2013 |
Full Text: PDF file (1.3 MB) |
Keywords: GNSS, ionosphere, ionospheric delay, TEC |
Abstract: The aim of this study was to assess the performance of several approximation techniques for ionospheric total electron content
(TEC) mapping. Approximation techniques based on data-fitting with local or general two-dimensional polynomials, local
planes or distance-dependent interpolation were applied and tested. For the ionosphere modeling, dual-frequency GPS data
from Polish GBAS system (ASG-EUPOS) were used, and TEC was estimated together with hardware delays from phasesmoothed
pseudoranges. Next, grids of vertical TEC values with spatial resolution of 0.25 degrees in both latitude and
longitude were generated using the evaluated approximation techniques. Subsequently the grids were used to create regional
TEC maps with 5-minute temporal resolution, and also to create ionospheric delay corrections for GPS positioning.
The quality of the resulting ionospheric maps was tested twofold, firstly by comparison to high-quality CODE global
ionosphere maps (GIM), which were generated using data from about 150 GPS sites of the International GNSS Service (IGS).
Secondly, by creating double-differenced ionospheric delay corrections and comparing them to reference values derived from
the reference network data processing. For the correction tests, two perpendicular baselines directed North-South (N-S) and
West-East (W-E) and reaching up to 100 km were selected. The approximation methods were analyzed with a special
emphasis on the diverse ionospheric conditions. For the testing, a quiet ionosphere day of 20 March 2012 and an active
ionosphere day of 9 March 2012 were selected. The results show that the regional models properly represent the changing
ionosphere, with the best results provided by data-fitting into local functions. |