2 pages, 1 figure.-- MARTECH23, 10th Marine International Workshop on Marine Technology, 19-20 de Junio de 2023, Castellón de la PlanaTwo designs of lagrangian low-cost drifting buoys have been developed in order to monitor the ocean surface dynamics in the North-west Iberian Peninsula and provide ground-truth observations that can be used to assess the performance of High Frequency (HF) Radars of RAIA observatory from 2020 to 2022. Since regression model type I, which is typically used in buoy-HF radar antennas validations, does not consider the presence of errors in the observations from both instruments, regression model type II was proposed to instrument intercomparison. Furthermore, a new metric was developed to better assess both model types regressions in lagrangian validationsThe authors also would like to thank the support from projects RADAR ON RAIA (0461_RADAR ON RAIA_1_E, co- funded by the European Union through EP-INTERREG V-A España-Portugal POCTEP program) and STRAUSS (PID2019-106008RB-C21) funded by MCIN/AEI/10.13039/501100011033N
