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1

Detection, identification and mitigation of outliers by solving observation equations with outliers as part of unknowns

Isshiki H.

Artificial Satellites : Journal of Planetary Geodesy

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2009

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Vol. 44, No. 1

1--19

EN

The conventional RAIM based on the least square algorithm of the residuals of the snapshot data can detect the single outlier with high probability, but it can miss the multiple outliers frequently. So, it invites a serious problem of the missed detection. We must clarify this problem, and develop a method to prevent the missed detection of the multiple outliers. In the present paper, a method to detect multiple outliers more correctly is discussed, and the numerical results seem much improved and appropriate.

2

Estimation of ionospheric delays in dual frequency GNSS positioning

Isshiki H., Wang J.

Artificial Satellites : Journal of Planetary Geodesy

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2008

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Vol. 43, No. 1

1--13

EN

The correct estimation of ionospheric delays is very important in precise satellite-based kinematic positioning, especially over long baselines. In the case of triple frequency system, the ionospheric delays can be estimated from the measurements. However, in the case of dual frequency system, the situation becomes more complicated. The precision of those ionosphere models supplied by the external information source such as JPL IONEX Data is not sufficient, as the high frequency component is neglected. The precision of the low frequency component is not sufficient for the use in long baseline kinematic positioning. On the other hand, the high frequency component can be estimated from the phase range measurements. If the low frequency components are estimated by using an external information source or pseudo-range measurements, more reasonable estimates of ionospheric delays may be possible. In this paper, the estimation using the pseudo-range measurements is discussed. The accuracy of the estimates for ionospheric delays is not sufficient at present because of the bias errors in the pseudo-range measurements. However, if the accuracy of the pseudo-range measurements is improved in future by GPS Modernization and GALILEO, the method would become very promising and convenient, since any external informations are needed and realtime estimation of ionospheric delays becomes possible.

3

A new algorithm for long baseline kinematic positioning with dual frequency GPS/GNSS receivers

Isshiki H., Wang J.

Artificial Satellites : Journal of Planetary Geodesy

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2006

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Vol. 41, No. 4

117--135

EN

Smoothing pseudo ranges with ionosphere-free combinations of phase ranges can be useful for long rang positioning, since this new smoothing process can significantly remove the effect of ionosphere delays in positioning applications. The smoothing process can be conducted without being affected by cycle slips, though it uses phase ranges. Therefore, it can provide a robust precise positioning solution which is not affected by cycle slips. The multipath effects may also be reduced, if the averaging interval taken is long enough. If the low frequency noise components and the hardware biases in pseudo ranges are reduced, the positioning performance with the smoothed pseudo ranges may be promising. In future GNSS receivers, both the noises and the hardware biases in pseudo ranges will be significantly reduced. Then, the positioning based on the proposed algorithm will be very useful.