can be obtained from an altimeter in an orbiting satellite. 

 It seems appropriate to review several ways in which 

 oceanographers can contribute information of value to the 

 geodesists, and then to discuss some ways in which the 

 satellite altimeter can contribute information of interest 

 to the oceanographers. There have been other recent reviews 

 of this topic in the so-called "Williamstown Report" by 

 von Arx (NASA, 1969), and by Greenwood, Nathan, Neumann, 

 Pierson, Jackson, and Pease (1969). I should emphasize 

 that the topics discussed here are not selected on the 

 basis of the precision of present altimeters; rather, I 

 will try to emphasize oceanographic problems that seem to 

 lend themselves well to a satellite program. 



A useful result for the present purpose is the geopotential 

 anomaly of the sea surface, relative to a deep pressure 

 surface, computed from the observed density distribution. 

 Maps of geopotential anomaly represent, to a good approximation, 

 the shape of the physical sea surface, relative to a level 

 surface. A map of the world ocean, Figure 1, has been given 

 by Stommel (1964, chart 1; or 1965, fig. 96c). The principal 

 features are the high regions associated with the tropical 

 anticyclonic circulations, and the low areas at high latitudes. 

 From the highest point, near Japan, to the Antarctic, the 

 total relief is 2 m. It also is evident that the Pacific 

 Ocean is somewhat higher than the Atlantic Ocean. 



Montgomery (1969) has dis'cussed ways in which the map 

 could be improved, through use of a deeper reference surface 

 and more modern data. The details of this map could be 

 changed, but the basic features are not likely to be in 

 error by more than about 30 cm. This error estimate will 

 be discussed below. 



The primary reason oceanographers have developed maps 

 such as this one is to learn something about the average 

 surface currents. For the simplest, steady flow, called 

 geostrophic motion, the horizontal momentum balance is between 



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