ABSTRACT 



Cubic spline interpolation is a mathematical procedure which is 

 an analog of the draftsman's plastic spline. The advantage of this 

 interpolation procedure over the more commonly used methods 

 such as Lagrange lies in its ability to not only fit each given data 

 value exactly but to maintain continuity of the first and second de- 

 rivatives. 



The relative accuracy of the cubic spline interpolation procedure 

 for generating gridded data values and estimates of mean gravity 

 anomalies from track-type geophysical surveys is shown to be ex- 

 cellent when applied to properly designed surveys. Techniques for 

 interpreting the two-dimensional Fourier transform in terms of track 

 spacing, track orientation, and down -track sampling rate are pre- 

 sented todemonstratetheeffect of these parameters on interpolation 

 accuracy. A procedure for utilizing closed form integration of the 

 bicubic spline surface to produce mean gravity anomalies is shown 

 to yield accuracies comparable to the method of averaging cubic 

 spline grid values. 



THOMAS M. DAVIS 

 ANGELO L. KONTIS 



Earth Physics Branch 



Hydrographic Development Division 



Ocean Engineering Department 



