Contouring gravity anomaly maps by digital plotter

Abstract

Contouring gravity anomalies by digital plotter given values at points on a square grid is achieved by two-way polynomial interpolation so that the interpolated values fit exactly at the grid points. Contours are drawn for one grid square at a time using the 2n × 2n array of grid values surrounding the square. The method of polynomial interpolation is designed to ensure continuity in the gradients of the contours across the boundaries of each square.