A New Method for converting Slant Ionospheric Delays to Vertical for SBAS Ionospheric corrections

Bongkwan Choi,Deokhwa Han,Changdon Kee,Hwigyeom Kim,D.D Wijaya

doi:10.1051/e3sconf/20199403002

Bongkwan Choi, Deokhwa Han + Show 3 more

Open Access

https://doi.org/10.1051/e3sconf/20199403002

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Abstract

SBAS gives ionospheric correction data to GNSS users for more accurate positioning. SBAS uses obliquity factor of thin shell model to convert slant ionospheric delays to vertical delays which is not precise especially at lower elevation angle. This paper suggests a new method for estimating the vertical delays which are needed for generating the ionospheric corrections. The new method uses Chapman profile assumption by which the vertical electron density distribution can be modeled. It is also assumed that Chapman profile’s parameters are given and the vertical ionospheric delay can be linearly modeled. We divided ionosphere into multi-layer and mapped ionospheric vertical delays with a linear function. Converting vertical delays of each layer to slant delays, we can set a linear equation for the vertical ionospheric delay at IPP. We used IRI model to get information about ionosphere for simulation to verify our new method. Estimation error of vertical ionospheric delay at IPP was decreased about 40% in average when using our new method.

Highlights

Global Navigation Satellite System (GNSS) is a system by which a user can point the user’s location
The correction data of ionospheric delay at Ionospheric Grid Point (IGP) is generated with the slant ionospheric delays in signal between satellites and reference stations
We suggested a new method for converting slant ionospheric delays to vertical ionospheric delay to mitigate the error of thin shell model

Summary

INTRODUCTION

Global Navigation Satellite System (GNSS) is a system by which a user can point the user’s location. To mitigate ionospheric errors in GNSS signal, the user can use ionospheric models such as Klobuchar or get information about ionospheric delay from a reference station. SBAS gives ionospheric correction data of Ionospheric Grid Point (IGP) and the user uses the information of IGP to calculate user’s ionospheric delay. The correction data of ionospheric delay at IGP is generated with the slant ionospheric delays in signal between satellites and reference stations. Master stations of SBAS need vertical ionospheric delays at Ionospheric Pierce Point (IPP), instead of slant delays, to calculate ionospheric correction data at IGP. Thin shell model does not consider spatial characteristics of ionosphere These factors occur errors in estimation of vertical ionospheric delay from slant ionospheric delay. We suggested a new method for converting slant ionospheric delays to vertical ionospheric delay to mitigate the error of thin shell model

Algorithm of the new method

Verification of the new method

Conclusion