Modeling of Ionospheric Delay for SBAS Using Spherical Harmonics Functions

• Autorzy: Han D. , Yun H. , Kee C.

Identyfikatory

DOI

10.12716/1001.07.02.07

• Języki publikacji: EN

Abstrakty

EN

In SBAS (satellite‐based augmentation system), it is important to estimate ionospheric delay accurately to guarantee userʹs 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.

Słowa kluczowe

EN

Consequences of Delays; Ionospheric Delay; satellite based augmentation system (SBAS)

• Wydawca: Faculty of Navigation, Gdynia Maritime University
• Czasopismo: TransNav : International Journal on Marine Navigation and Safety of Sea Transportation
• Rocznik: 2013
• Tom: Vol. 7, no. 2
• Strony: 205--209
• Opis fizyczny: Bibliogr. 6 poz., rys., tab.

Twórcy

autor

Han D.

• Mechanical and Aerospace Engineering and the Institute of Advanced Aerospace Technology, Seoul National University, Korea

autor

Yun H.

• Mechanical and Aerospace Engineering and the Institute of Advanced Aerospace Technology, Seoul National University, Korea

autor

Kee C.

• Mechanical and Aerospace Engineering and the Institute of Advanced Aerospace Technology, Seoul National University, Korea

Bibliografia

• [1] 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
• [2] Yongjin Moon, “Evaluation of 2‐Dimensional Ionosphere Models for National And Regional GPS Networks in Canada”, M.Sc. Thesis, University of Calgary, 2004
• [3] 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
• [4] 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
• [5] 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
• [6] 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