Second-order ionospheric effect on PPP over Hong Kong

In this study, the effect of high-order ionospheric error, the second-order one, on PPP has been evaluated in Hong Kong, a low latitude area. First, a method regarding how to calculate second-order ionospheric error is introduced and the evaluation method is also discussed. After that, the numerical results are shown. Based on the results, it is found that the effect of the second-order ionospheric error on ionosphere-free carrier phase combination measurements reached up to the cm level in 2001 and the effect of the second-order ionospheric error on both kinematic and static PPP also reached the cm level. Further, it is also demonstrated that the effect of second-order ionospheric error on PPP is closely related to solar activity.