Impact of Approximate Implementation manner in Klobuchar Model

Aghyas Aljuneidi Aghyas Aljuneidi,Hala Tawfek Hasan Hala Tawfek Hasan

doi:10.4401/ag-8507

Abstract

This paper focuses on the approximations that John A. Klobuchar made in mid 70s in his famous algorithm of ionospheric correction model for single frequency GPS receiver. At that time Klobuchar used a system of fixed geomagnetic north pole coordinates which are not accurate nowadays according to the International Geomagnetic Reference Field and to the World Magnetic Model because the geomagnetic poles move slowly. In addition, Klobuchar had to do other trigonometry simplifications in his implementation to avoid sophisticated computations. In order to evaluate this approximate implementation in a single frequency GPS receiver, ionospheric time and range delay are estimated on the entire day of January 1st 2010, using a different implementation in MATLAB. The required GPS data is obtained from recorded RINEX files at UDMC near DAMASCUS, SYRIA. In this comparative study, we reformulated the standard equations of Klobuchar model and examined the influence of its approximations on the ionospheric range delay and found a non- negligible bias in order of ten centimeters, whereas the influence of the movement of the geomagnetic poles was in order of few centimeters.

Highlights

Global Navigation Satellite Systems (GNSSs) began after the launching of Sputnik, the first artificial satellite, by the Soviet Union in 1957, which was very motivating for the US scientists
Numerical applications were done in aim to estimate the impact of approximate implementation of Klobuchar model, and analytical studies were performed to evaluate the impact of the non-exact values of geomagnetic north pole coordinates, we did many comparisons in these two aspects:
The approximate implementation where the used geomagnetic north pole coordinates are those of the original Klobuchar model, i.e., λ0 = 291E and φ0 = 78.3N

Summary

Introduction

Global Navigation Satellite Systems (GNSSs) began after the launching of Sputnik, the first artificial satellite, by the Soviet Union in 1957, which was very motivating for the US scientists. Tracking of Sputnik by using the Doppler shift inspired the idea to track a receiver’s position on Earth by acquiring a certain modulated radio frequency emitted by satellites. Starting by the first satellite navigation program, named TRANSIT, and because of its numerous weaknesses, the US in mid 70s released its first Global Positioning System in the world, named GPS, which still operate today and is subject to continuous modernizations. The fundamental principle of satellite positioning is based on the measurements of the signal transit time between the satellite and the receiver, the GPS system uses the L band frequencies 1575.42 MHz, 1227.6 MHz and recently 1176.45 MHz for the transmission of data

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