Theoretical (lines) and measured (squares) elevation plots for the GPS satellite PRN 18. The GPS-IRT (θt = –1.6°) model is for an 11.7-cm-thick snow layer with a snow density of 0.09 g∙cm-3 (SWE = 1.05 g cm-2). The GPS-IR (θt = 0°) model is for a 17.5-cm-thick snow layer with a snow density of 0.14 g∙cm-3 (SWE = 2.45 g∙cm-2). The fixed parameter values are given in Table 1. Snow permittivity values (ϵ1) of 1.18 - i 7.65 × 10-5 and 1.28 - i 0.924 × 10-4 are used in the GPS-IRT (θt = –1.7°) and GPS-IR (θ
= 0°) models, respectively. The GPS times for the measurements are 22:20 to 23:30.