Abstract:Corrected by high-order ionospheric delay, observations are used to estimate satellite orbits and clocks. And the other site’s tropospheric delay is calculated by these orbits and clocks. The results show that it is easy to reach 1cm value in the second-order ionosphere at low latitude areas. This can cause 2-3 mm error to troposphere estimation. But the third-order ionosphere estimation typically cannot exceed 5 mm at low latitude areas. A data test implies that if 1 mm precision of troposphere estimation is desirable, then the site’s second-order ionosphere computation must be corrected in middle and low latitude areas. Since the third-order ionosphere computation effect on troposphere estimation is very small, it can be safely neglected.