TINs

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In addition to using rectangular grid DEMs, Maptitude can work with elevation data that is distributed across arbitrary points. Maptitude performs this by creating a Triangulated Irregular Network (TIN) that allows the point data to be interpolated. The data can then be contoured or gridded as a conventional 2d layer, and it can be used to create a terrain surface.

This page shows you how to create a conventional contoured 2d layer. The next page shows you how to create a surface from a TIN dataset.

Here we have an input point dataset depicting crustal uplift from various tidal gauges around Fenno-Scandinavia (from the European Geotraverse):

The input data points for the TIN

The uplift measurements (in mm/yr) are also displayed. We shall create a TIN and contour these values across Fenno-Scandinavia.

Make the imported point layer (uplift) the current working layer, then select Toolbox on the Tools->Surface Analysis sub-menu. Because the layer does not have the required surface (i.e. TIN) information, Maptitude will display the Surface Analysis dialog box so that you can create it:

The Settings panel on the Surface Analysis dialog box

The Settings tab tells Maptitude how to create the TIN. Typically you will restrict in the input point features to only those that are visible. The data that we wish to contour is stored on the uplift field, and it is measured in millimeters.

The Options tab should also be set:

The Options tab on the Surface Analysis dialog box

Data interpolated from a triangulation will tend to produce angular output data. One solution is to apply a smoother. Do this by setting the Smoothing Level. Here we use a smoother of ‘2’. Maptitude can also draw a convex hull outline around the data points to demonstrate the data extents. Set the Outline check box if you wish to see this.

Press OK when these have all been set, and Maptitude will display the Surface Analysis Toolbox:

The Surface Analysis Toolbox

This toolbox can be used to create a grid, a 3d surface, or a set of contours. Press the contour button (middle button with blue numbers) to display the Contour Layer dialog box:

The Contour Layer dialog box

The contours will be drawn as a new layer. You can select if the contours will be drawn just as lines, or lines with color shading; and whether the contour intervals are automatic or manual. The defaults are okay here. Press OK and Maptitude will ask you for the output CDF file for the new layer, before creating the contour layer. Here are the resulting contours:

The final contour results from the TIN

The contours have been inserted into a new layer called Contour Areas.  As expected, the uplift is higher (orange) in the middle where the point values are higher.

TINs like this can also be constructed for elevation data and used to display 3d surfaces.

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