Sixty-two temperature sections were taken to depths of 800 m by aircraft along Geosat ground tracks within 1--2 days of the satellite orbit. The sections are 500--700 km long and cross the Gulf Stream and its rings. From pairs of sections that repeat on the same ground track, collinear differences of geopotential anomaly (0/25 MPa) and the depth of the 16 ¿C isotherm were collected as along-track signals of the change of baroclinic conditions. The corresponding collinear differences of sea elevation were collected from the Geosat orbits. These difference signals, from aircraft and altimeter, were fit to one another along common ground track segments by removing residual orbit error as a tilt and bias and proportionally scaling the magnitudes of the signals. The ratio of geopotential anomaly to sea elevation by this method is 0.84¿0.10 dyn m m-1. That is, fluctuations of geopotential anomaly which correlate to sea elevation across the Gulf Stream are smaller by this proportional value. The difference of this ratio from unity is consistent with a barotropic signal of about 0.10 m, as estimated from reported measurements of abyssal velocity under the stream. Because the uncertainties in the aircraft data are of the same order as the scatter in the calibration, it is unclear whether greater precision is impeded primarily by these uncertainties or by random barotropic signals. The ratio of the displacement of 16 ¿C to sea elevation is 480¿75. ¿ American Geophysical Union 1992