Estimation Error of Traveling verocity of ARGOS Drifters

Abstract

In order to estimate the errors in posiotioning and determining the velocity of ARGOS platforms, the records of latitude and longitude of nine platforms which were located in the office of Hydrographic Department are statisticaly analyzed. Data of distance between satellite-determined position and the located position are also analyzed. It is shown that both histograms of latitude deviation and longitude-deviation from those of the located position are agreed well with the normal distribution, respectively. Probability density functions for velocity as well as distance, therefore, are subjected to x (kai) -distribution with second degrees of freedom. Obtained histograms of velocity and distance are likely similar to such x distributions. For the data of this study, averaged error of spurious velocity of motionless ARGOS platforms, which are caused by satellite-positioning error itself and irregularity of time-interval for posiotioning, is estimated to be about 7cm/sec with standard deviation of 7. 4cm/sec. Thus, individual drifting velocity of surface drifter in adjacent sea to Japan, is considered to include above order of velocity error.