TIN Interpolator - MapBasic - 2023

The TIN Interpolator works best for terrain data and for data points that have a linear progression or relationship to each other across the grid, such as elevation or temperature. The TIN Interpolator produces triangles from a network of points that more closely reproduces the original map terrain than the IDW Interpolator. It draws lines between points, dividing them into triangles and connecting all the points that it can. It creates a mesh of connectivity so that the grid points can be interpolated. The interpolation is not influenced by the neighboring original data values, so you do not get the "false bumping" of data that you can get with the IDW Interpolator.

The TIN settings can be manipulated to give more or less detail to the map terrain. The Tolerance setting controls whether closely spaced points are discarded. The tolerance is a fraction of the diagonal length of the bounding box of the points. The Distance value controls the output. For non-zero distance values, only edges or triangles contained within a sphere centered at mesh vertices are output. This is useful to constrain the triangulated irregular network to a specified distance; otherwise, the triangulation will cross concave regions. The Feature Angle setting controls the angle (in degrees) that defines a sharp edge. This setting is used for smoothing the final grid. If the difference in angle across neighboring polygons is greater than this value, the shared edge is considered "sharp."

The TIN Interpolator settings can be controlled via the Settings button in the Create Thematic Map - Step 3 of 3 dialog when creating a grid thematic map. The cell size number in this interpolator settings dialog represents both the height and width of the cell like the IDW method. Any change to the cell size will result in an automatic update of the grid dimensions.

TIN Interpolator Settings for Create Grid Statement

For the MapInfo Pro TIN Interpolator, when specifying the following parameters in the Grid Statement syntax:

		Using num_parameters parameter_name : parameter_value 
		[ parameter_name : parameter_value ... ] 

the following parameter_name : parameter_values may be used:

• "TOLERANCE": "number" – Must be equal to or greater than .0001 and less than or equal to .01, default setting is .005.
• "DISTANCE": "number" – Must be greater than zero and less than height and width of grid .
• "FEATURE ANGLE": "number" – Must be equal to or greater than zero and equal to or less than 180, default setting is 25 degrees.
• "MIN POINTS": "number" – Must be greater than zero, default setting is 1. The minimum points required for calculating value of a grid cell.
• "MAX POINTS": "number" – Must be greater than zero, default setting is 25. The maximum points used for calculating value of a grid cell.
• "GRID HEIGHT": "number" – Must be greater than zero, default setting is 100. The minimum height of grid in cells. The result is affected by aspect ratio, but height in cells result should be a minimum of this value.
• "GRID WIDTH": "number" – Must be greater than zero, default setting is 100. The minimum width of grid in cells. The result is affected by aspect ratio, but width in cells result should be a minimum of this value
• "CELL SIZE": "number" – Size of grid cell in distance units. Must be greater than zero and default size is 100, if not specified.

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