New Progress and Application Prospects of Global Navigation Satellite System Reflectometry (GNSS+R)

The Global Navigation Satellite System (GNSS) has the characteristics with all-weather, near real-time and high precision observations. It can transmit L band signals continuously, which has been widely used in positioning, navigation and timing (PNT). With the development of GNSS technology, recently GNSS reflected signals can be used to detect Earth's surface characteristics, i.e., GNSS reflectometry (GNSS+R). Combined with GNSS receiver antenna position and medium information, surface roughness and characteristics can be determined by using delay measurements. As a hotspot in GNSS and remote sensing field, GNSS+R has achieved a number of progress and results. In this paper, the principles and methods of GNSS+R are presented as well as their latest advances, including various techniques, methods and remote sensing applications in the ocean, land, hydrological, vegetation and ice and snow, especially the latest progresses in BeiDou-R and TDS-1 GNSS+R. Finally, the future applications and prospective of GNSS+R are given, including multi-GNSS system, new GNSS-R receivers, GNSS+R missions and emerging applications.