Evaluation of Ionospheric Interpolation Algorithms for Regional and National GPS Networks in Canada

Y. Moon, and S. Skone

Abstract:	The purpose of this paper is to determine a 2-dimensional ionosphere model, applicable in real-time, that provides optimal accuracy of vertical delays at ionospheric grid points (IGPs). This model is based on GPS delays measured at ionospheric pierce points (IPPs), as observed from dual-frequency GPS tracking stations. Two algorithms are selected for possible implementation: spherical harmonic model and thin plate spline interpolation. These methods are based on twodimensional estimation on an ionospheric shell at 350 km altitude. The input observations are computed as slant delays using dual frequency GPS observations. In the spherical harmonics model, the coefficients and receiver differential code biases are estimated every 5 minutes in a real-time mode using a Kalman filter. Thinplate spline is a 2-dimensional generalization of the cubic spline in 1 dimension. The basic idea of this method is to build a function which passes through the grid points and minimizes the roughness of the surface. The performance of the two algorithms is evaluated in terms of accuracy of the residuals between observed vertical TECs (VTECs) and estimated VTECs at IGPs in two GPS networks: Canadian Active Control System (CACS) and Western Canada Deformation Array (WCDA). The impact of ionospheric conditions on each algorithm is also assessed by processing data from the period May 28–May 31, 2003 when a severe geomagnetic storm occurred. The spatial and temporal variation of the geomagnetic storm is also investigated by plotting vertical TEC maps over Canada.
Published in:	Proceedings of the 2004 National Technical Meeting of The Institute of Navigation January 26 - 28, 2004 The Catamaran Resort Hotel San Diego, CA
Pages:	761 - 770
Cite this article:	Moon, Y., Skone, S., "Evaluation of Ionospheric Interpolation Algorithms for Regional and National GPS Networks in Canada," Proceedings of the 2004 National Technical Meeting of The Institute of Navigation, San Diego, CA, January 2004, pp. 761-770.
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