HomePage
 




 


 

ISSN 2083-6473
ISSN 2083-6481 (electronic version)
 

 

 

Editor-in-Chief

Associate Editor
Tomasz Neumann
 

Published by
TransNav, Faculty of Navigation
Gdynia Maritime University
3, John Paul II Avenue
81-345 Gdynia, POLAND
www http://www.transnav.eu
e-mail transnav@am.gdynia.pl
Modeling of Ionospheric Delay for SBAS Using Spherical Harmonics Functions
1 Seoul National University, Korea
ABSTRACT: In SBAS (satellite-based augmentation system), it is important to estimate ionospheric delay accurately to guarantee user's accuracy and integrity. Grid based ionospheric models are generally used to estimate ionospheric delay for SBAS. In grid based model, SBAS broadcasts vertical ionospheric delays at the grid point, and users get their ionospheric delay by interpolating those values. Ionospheric model based on spherical harmonics function is another method to estimate ionospheric delay. This is a function based approach and spherical harmonics function is a 2-D fourier series, containing the product of latitude dependent associated Legendre functions and the sum of the longitude dependent sine and cosine terms. Using ionospheric delay measurements, coefficients for each spherical harmonics functions are estimated. If these coefficients are known, user can reconstruct ionospheric delay. In this paper, we consider the spherical harmonics based model and propose a ionospheric delay estimation strategy for SBAS that can be used to mitigate ionospheric delay estimation error, especially in storm condition. First, coefficients are estimated under initial order and degree. Then residual errors for each measurement are modeled by higher order and degree terms, then coefficients for these terms are estimated. Because SBAS message capacity is limited, in normal condition, initial order terms are only used to estimate ionospheric delay. If ionospheric storm is detected and there is need to mitigate the error, higher order terms are also used and error can be decreased. To compare the accuracy of spherical harmonics based model with grid based model, some post-processing test results are presented. Raw observation data is obtained from RINEX format and the root mean square(RMS) and max value of residual errors are presented.
REFERENCES
D. Venkata Ratnam, CH. Sufjatha, A.D. Sarma, Shudha Ravindran, “Modelling of GAGAN TEC data using Spherical Harmonic Functions”, International Converence on Computers and Devices for Communication, 2009
Yongjin Moon, “Evaluation of 2-Dimensional Ionosphere Models for National And Regional GPS Networks in Canada”, M.Sc. Thesis, University of Calgary, 2004
Jiyun Lee, Sungwook Jung, Eugene Bang, Sam Pullen, Per Enge, “Long term monitoring of ionospheric anomalies to support the local area augmentation system”, ION GNSS 2010, Potland, September 2010, pp. 2651-2660
Alexandru Ene, Di Qiu, Ming Luo, Sam Pullen, Per Enge, “A Comprehensive Ionosphere Storm Data Analysis Method to Support LAAS Threat Model Development”, ION NTM 2005, San Diego, CA, 24-26 January 2005, pp. 110-130
V.B.S. SRILATHA INDIRA DUTT, G. SASIBHUSHANA RAO, “2-D Electron Density Profile of the Ionosphere Using the Modified Spherical Harmonics Analysis”, The NEHU Journal, Vol IX, No.2, July 2011, pp. 87-96
Byung-Kyu Choi, Woo Kyung Lee, Sung-Ki Cho, Jong-Uk Park, Pil-Ho Park, “Global GPS Ionospheric modeling using spherical harmonics expansion approach”, Jounal of Astronomy and Space Sciences, 2010, pp. 359-366
Citation note:
Han D.H., Yun H., Kee C.: Modeling of Ionospheric Delay for SBAS Using Spherical Harmonics Functions. TransNav, the International Journal on Marine Navigation and Safety of Sea Transportation, Vol. 7, No. 2, doi:10.12716/1001.07.02.07, pp. 205-209, 2013

Other publications of authors:


File downloaded 1504 times








Important: TransNav.eu cookie usage
The TransNav.eu website uses certain cookies. A cookie is a text-only string of information that the TransNav.EU website transfers to the cookie file of the browser on your computer. Cookies allow the TransNav.eu website to perform properly and remember your browsing history. Cookies also help a website to arrange content to match your preferred interests more quickly. Cookies alone cannot be used to identify you.
Akceptuję pliki cookies z tej strony