| description abstract | This study investigated long-term observations from three pairs of closely spaced, continuously operating reference stations (CORS): STVI and VITH (2008–2014, 0.6 km apart), BYSP and PRHL (2008–2014, 3.2 km apart), and CRO1 and VIKH (1995–2014, 23 km apart), in the region of Puerto Rico and Virgin Islands. The Global Positioning System (GPS) antennas of STVI, BYSP, and CRO1 are mounted on ground-based monuments. The GPS antennas of VITH, PRHL, and VIKH are mounted on building-based monuments. This study indicated that there is no considerable difference between building-based and ground-based CORS with regard to the precision of daily positions and the reliability of long-term site velocities. The amplitude of thermal movements associated with daily temperature changes and the wind drift associated with air pressure change from a 2-story concrete building fell below the detectable levels of the present high-precision GPS technique determined by Precise Point Positioning (PPP) processing. Further analysis indicated that (1) building-based CORS can retain more complete GPS observations and provide a more stable multipath environment, and (2) the large and heavy mass of the building and its foundation can decrease the amplitude of seasonal signals and filter certain short-period motions. As a result, the building-based CORS have the potential to perform better than the ground-based CORS as long as their monuments are firmly fixed on 1-story or 2-story concrete buildings and the buildings themselves are stable. | |
