Offshore sea levels measured with an anchored spar-buoy system using GPS
Conventional tide gauges are usually housed along the coast. Satellite
altimetry works well in the open ocean but poorly near the coast due to
issues such as signal contamination by land returns. These limitations
lead to an observational gap in the coastal ocean. Using data collected
by a GPS installed on top of an anchored spar-buoy in Tampa Bay, we
retrieved water levels through a combination of precise positioning and
interferometric reflectometry. Individual water level retrievals agree
with a nearby acoustic tide gauge at ~16 cm level.
Amplitude and phase of the major tidal constituents are well recovered
by the GPS spar-buoy measurements. Over a 2-year period, agreement of
daily mean sea levels measured by the GPS spar-buoy and a nearby
acoustic tide gauge is 3.1 cm. When sea level data measured by the GPS
spar-buoy are included in the coastal ocean circulation model,
low-frequency error propagated from the open boundary is reduced.