Tsukuba GPS Dense Net Campaign Observations: Comparison of the Stacking Maps of Post-fit Phase Residuals Estimated from Three Software Packages

Abstract

The characteristics of post-fit residuals computed using three types of software have been investigated, and the behavior of multipath errors in the post-fit phase residuals evaluated. GPS data observed during the Tsukuba GPS dense net campaign were analyzed, and the post-fit phase residuals of the linear combination of the L1 and L2 GPS phase measurements carrier wave (LC), computed using the three software packages were studied. The post-fit phase residuals were stacked, and their mean value for each site was obtained, with a resolution of 1° × 1° for the azimuthal and elevation angles, respectively. The skymaps of the stacked post-fit phase residuals showed similar patterns among the three types of software. A random error index was introduced to evaluate random errors in the post-fit phase residuals, which showed twice as large errors using the point positioning strategy, as those obtained using the double difference strategy. The oscillation patterns shown in the stacking map were similar to those simulated using the Elosegui's multipath model (1995). This suggests that the pattern arose from multipath errors. When the stacking maps were introduced into the post-fit phase residuals, the impact of the resulting post-fit phase residuals was significant at sites that showed large multipath errors. The point positioning strategy still contained random errors that were twice as large as the double difference strategy errors. Multipath errors induced biases in the zenith tropospheric delay, which resulted in larger biases of the absolute slant tropospheric delay reconstruction at lower elevation angles. This suggests the importance of introducing stacking maps in GPS analysis.