Ten years of Lake Taupo surface height estimates using the GNSS interferometric reflectometry

A continuously operating GNSS station within a lake interior is uncommon, but advantageous for testing the GNSS Interferometric Reflectometry (GNSS-IR) technique. In this research, GNSS-IR is used to estimate ten years of lake surface heights for Lake Taupo in New Zealand. This is achieved using data collected from station TGHO, approximately 4 km from the lake's shoreline. Its reliability is assessed by comparisons with shoreline gauges and satellite radar altimetry lake surface heights. Relative RMS differences between the daily averaged lake gauge and GNSS-IR lake surface heights range from +/- 0.027 to +/- 0.028 m. Relative RMS differences between the satellite radar altimetry lake surface heights and the GNSS-IR lake surface heights are +/- 0.069 m and +/- 0.124 m. The results show that the GNSS-IR technique at Lake Taupo can provide reliable lake surface height estimates in a terrestrial reference frame. A new ground-based absolute satellite radar altimetry calibration/validation approach based on GNSS-IR is proposed and discussed.