Triangulation Gridding

Triangulation-based gridding works like this: The data points are connected into triangles by imaginary lines, with one data point at each triangle vertex, and the triangles as close as possible to equi-angular. Once the imaginary network is determined, the slope of each triangle is computed from the three X, Y, and Z corner points. The grid nodes that lie within each triangle are assigned a z-value based on their intercept with the sloping triangular plane.
Those grid nodes that lie outside the triangle network can be assigned values using the Inverse-Distance gridding method, with a weighting exponent of "2" and quadrant searching turned off.

Advantages: This method honors the control points. Unlike the non-grid method of triangulation used in the Easy Map contouring, this method creates a data grid upon which 3D maps can be generated.

Disadvantages: Contours tend to be angular, and the process can be slow for large data sets.

Menu Options

• Interpolate Edge Points: If activated, this will force the program to insert points along the edge of the study area so that the contours can be drawn to the edge. It does this by inserting 5 points at equal spacing along the map boundaries (with one in each corner) and assigning them a value using the Inverse-Distance squared gridding method. These new points can then be used when drawing the triangle network, assuring that all edges and corners are included within the network.

• 

• No Edge Interpolation: If you select this option, expand this heading to enter the Default Z Value which will be assigned to the nodes outside the triangular network.
  • Default Z = Null (Undefined): Choose this item to assign null values to the nodes outside the network.
  • Default Z = User Defined: Click on this item to type in the value that will be assigned to the grid nodes that lie outside the control area.
    

Back to Grid Method Summary

RockWare home page