A Simple Method for the Comparison of Adjacent Points on Thematic Maps

Abstract

A simple method is outlined for comparing adjacent grid points that have been measured for a series of maps. It is generalized and can be calculated for different types of maps where the original data are continuous or discrete. Either original or standardized data can provide the input information; standardization expresses the various maps in the same units. Next, similarities or differences are computed for all adjacent points from east to west and from north to south on the grid. The coefficients computed include correlation coefficients, Euclidean distances, and Mahlanobis distances; however, other statistics could be employed where appropriate. The coefficients then are plotted on the grid and contoured to depict the distribution of similarities and differences. Various patterns of similarities and differences between the points are shown by different coefficients and standardizations which can be related to geologic features underlying the original data. The maps of the point-to-point comparisons are suitable for subsequent study with other methods such as trend surfaces, filtering, or Fourier analysis. The example given is based on five structure contour maps from the Paleozoic of Kansas.