Updated from Version 2 comparisons.
The Pathfinder colinear sea surface heights were compared to ground truth data collected at tide gauges. For a given tide gauge, the daily values were compared to the altimeter heights at a chosen location of the colinear ground track. The altimeter location was chosen by minimizing the distance from the tide gauge while maximizing the number of cycles of valid data. The tide gauge data were interpolated at the time of the altimeter observation, which in turn has been corrected for all instrument and media biases, as well as surface models ( tide effects removed ). The mean of each time series was removed and the residual series were differenced. The RMS and the correlation values of these differences are shown at the geographic location of the gauges and in the histogram below for all three altimetric missions.