GNSS, which encompasses systems like GPS, GLONASS, and Galileo, is fundamental to a myriad of applications ranging from everyday navigation to intricate scientific research. The accuracy of these systems is paramount, and one significant factor affecting this accuracy is the tropospheric delay.

The Earth's troposphere, the lowest atmospheric layer, contains water vapor and other elements that refract satellite signals, leading to delays. These delays are traditionally accounted for using Zenith Tropospheric Delay (ZTD) and a mapping function that adjusts ZTD based on the satellite's elevation angle. However, these models often assume that the troposphere's impact on signals is uniform (isotropic) or, at best, predictably variable (anisotropic).

The study from Shandong University introduces a different approach by asserting that SPDs are non-isotropic with respect to azimuth angles. This insight challenges the longstanding isotropy and anisotropy models in tropospheric delay calculation.

Read more in Spacedaily article