Trend Surface Analysis-a Review

Earth scientists have always been interested in the description and analysis of surfaces, particularly those which serve to describe mapped data. The methods used in this context fall into two categories, written descriptions (using terms such as dip, strike, plunge, isoclinal folding, attitude of axial plane, iaiiation etc.1 and mathematical approximations. To overcome the inadequacies of verbal descriptions, earth scientists have turned to the more consistent and objective techniques of numerical approximation. The transition to the mathematical approach was essentially synchronous with the advent of fairly sophisticated computer Programs which made practical the highspeed computation of large matrices and the generation of complex functions.