Theoretical (lines) and measured (squares) elevation plots for the GPS satellite PRN 15. The GPS-IRT (θt = –1.7°) model is for a 13.0-cm-thick snow layer with a snow density of 0.08 g∙cm-3 (SWE = 1.04 g cm-2). The GPS-IR (θt = 0°) model is for an 18.3-cm-thick snow layer with a snow density of 0.12 g∙cm-3 (SWE = 2.2 g∙cm-2). The fixed parameter values are given in Table 1. Snow permittivity values (ϵ1) of 1.16 - i 5.88 × 10-5 and 1.24 - i 1.26 × 10-4 are used in the GPS-IRT (θt = –1.7°) and GPS-IR (θt = 0°) models, respectively. The GPS times for the measurements are 20:33 to 21:38.