A spar buoy-mounted ADCP measurement station in the Ligurian Sea: a metrological approach to correct current measures for bias effects and evaluate uncertainties

Improved Current Estimates from Spar Buoy-Mounted ADCP Measurement Station: A Case Study in the Ligurian Sea

“…contrary, the model does not represent well the significant increase in the northern component, clearly noted by the ADCP around the 23 June 2017. Comparisons with historical data and numerical models need to be supported by a proper uncertainty analysis (section C in [9]). If on one hand the standard uncertainty associated to the heading correction can be calculated by applying the law of uncertainty propagation [19], on the other the spherical law of cosines used to calculate the buoy apparent current is clearly a nonlinear model: therefore, due to correction for buoy apparent currents, standard uncertainties of both net current velocities and their directions need to be calculated in accordance to Monte Carlo method [20], as a by-product of the propagation of the normal probability distributions modeling buoy latitude and longitude values (i.e., the input quantities by which buoy bearing and displacement, and consequently its velocity, are derived).…”

“…In accordance with procedure described in detail in [9], to ensure the correct matching between ADCP and buoy data (acquired at half an hour and every hour, respectively) it is necessary to interleave the data of the latter, in terms of its heading and GPS longitude-latitude values. Velocity vector (in terms of modulus and bearing) associated with buoy displacement can then be calculated by applying the well-known spherical law of cosines formula [9,10].…”

“…First of all, since ADCP compass values could be potentially influenced by the presence of the metal body of the buoy, the ODAS heading measures were adopted as a reference and consequently the correction to be adopted on the ADCP measures is eval- In accordance with procedure described in detail in [9], to ensure the correct matching between ADCP and buoy data (acquired at half an hour and every hour, respectively) it is necessary to interleave the data of the latter, in terms of its heading and GPS longitudelatitude values. Velocity vector (in terms of modulus and bearing) associated with buoy displacement can then be calculated by applying the well-known spherical law of cosines formula [9,10].…”