Machine Contouring, Pitfalls and Solutions: Guide for Explorationists

Jeffery M. Yarus, James Lewis

Hand-contouring methods are quickly being replaced by sophisticated computer programs. Such programs are affordable and offer advantages such as speed and quality of graphic display. However, many geoscientists are reluctant to invest in the time to properly learn these systems, and they remain skeptical about the reliability of the final product.

Simple procedures can be used that allow users to quickly learn a system while determining the limitations of any contouring algorithm. This nonmathematical approach uses known surfaces (dipping planes, simple parabaloids, etc) sampled in a variety of ways (evenly spaced, random, clustered, and linear point). The approach helps identify subtle and misleading artifacts, which are a function of the mathematics and distribution of the data. This method measures the integrity of different algorithms under varying conditions.

Real geologic surfaces can be mapped accurately by first isolating and mapping the regional component. Such surfaces are commonly simple and easily recognized, much like those mentioned above. Since this component is the surface element most likely to be described accurately, the algorithm and corresponding estimates for grid size, weighing exponents, and other key mapping variables can be used as defaults for mapping the real data. The final map tends to be devoid of mathematical artifacts and similar to one produced by a conservative but experienced hand.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.