Changes

Because geological data are rarely presented on a uniform grid and are most often irregularly distributed across the map area, the number of control points used to estimate values at grid nodes is an important consideration. Several search procedures have been devised and are included in most mapping packages. These include nearest neighbor, circular, quadrant, and octant searching.

Because geological data are rarely presented on a uniform grid and are most often irregularly distributed across the map area, the number of control points used to estimate values at grid nodes is an important consideration. Several search procedures have been devised and are included in most mapping packages. These include nearest neighbor, circular, quadrant, and octant searching.

Nearest neighbor searching uses the nearest neighbors of a grid node to estimate nodal values. The number of neighbors to use can be decided arbitrarily or can be taken as nearest neighbors defined by a Delaunay triangulation of the control point set. The number of nearest neighbors determined from irregularly spaced control points can vary so that each grid node can be estimated from different numbers of control points depending upon their distribution across the map area. Figure 5 is a contour representation of the same data used in [[:file:introduction-to-contouring-geological-data-with-a-computer_fig3.png|Figure 3]] using nearest neighbor search and a 13 × 13 grid ([[:file:introduction-to-contouring-geological-data-with-a-computer_fig6.png|Figure 6]]).

Nearest neighbor searching uses the nearest neighbors of a grid node to estimate nodal values. The number of neighbors to use can be decided arbitrarily or can be taken as nearest neighbors defined by a Delaunay triangulation of the control point set. The number of nearest neighbors determined from irregularly spaced control points can vary so that each grid node can be estimated from different numbers of control points depending upon their distribution across the map area. [[:file:introduction-to-contouring-geological-data-with-a-computer_fig5.png|Figure 5]] is a contour representation of the same data used in [[:file:introduction-to-contouring-geological-data-with-a-computer_fig3.png|Figure 3]] using nearest neighbor search and a 13 × 13 grid ([[:file:introduction-to-contouring-geological-data-with-a-computer_fig6.png|Figure 6]]).

Circular, quadrant, and octant neighborhood searching procedures attempt to balance the number and distribution of control points used to estimate each grid node. Most mapping packages include procedures to estimate density and control point spacing, and these statistics should be examined carefully before deciding on search criteria for a particular project.

Circular, quadrant, and octant neighborhood searching procedures attempt to balance the number and distribution of control points used to estimate each grid node. Most mapping packages include procedures to estimate density and control point spacing, and these statistics should be examined carefully before deciding on search criteria for a particular project.