In this study, low-cost software-defined GPS and SBAS Reflectometry (GPS&SBAS-R) systems have been built and proposed to measure ocean-surface wave parameters on board the research vessel New Ocean Researcher 1 (R/V NOR-1) and other ground-based coastal stations of Taiwan. A power-law ocean wave spectrum model has been used and applied with the Small Perturbation Method (SPM) approach to solve the electromagnetic wave scattering problem from rough ocean surface and compare with experimental seaborne GPS&SBAS-R observations. Meanwhile, the intensity scintillations of high-sampling GPS&SBAS-R signal acquisition data are thought to be caused by the moving rough surfaces of the targeted oceans. We found that each derived scintillation power spectrum is a Fresnel filtering result on sea/ocean-surface elevation fluctuations and depends on the First Fresnel Zone (FFZ) value and the ocean-surface wave velocity. The determined ocean-surface wave parameters, e.g. wave velocity and spectral index, have been compared and validated against nearby buoy measurements.