Modified GNSS-PIR and Initial Verifications From the Perspective of Altimetry

This article proposed a modified structure of global navigation satellite system (GNSS) pseudointerferometric reflectometry (GNSS-PIR). The combination of the direct and reflected signals at the front end was modified as the combination of their coherent sums in the baseband so that GNSS-PIR could be more conducive under the framework of conventional GNSS reflectometry. To verify its feasibility, two altimetry experiments were carried out, over land and water surfaces, respectively. Strong oscillations were observed in GNSS-PIR waveforms from both scenes. Altimetry results showed that GNSS-PIR achieved ∼5 cm precision over land surface and ∼4 cm precision over water surface. It indicated that GNSS-PIR was available for retrieving parameters related to reflector height, such as water level and soil moisture.