TIN

Generating TIN

In surface modeling through triangle irregular grid, each polygon of a polyhedron face is a triangle. The triangle vertexes are generally surface sampled points. This modeling, considering triangle sides, allows that important morphological information such as discontinuity represented by linear shapes of tops and valleys are considered during triangle grade generation, making possible model a terrain surface keeping surface geomorphic shapes.

The redundancy number is drastically reduced if compared to the rectangle grid, once the grid is thinner in regions of big variations and more spaced in almost plane regions. Surface discontinuities can be modeled through characteristics lines and points.

This grid has the advantage to use its own sampled points to model the surface, with no need of any type of interpolation. The disadvantage of irregular grid is the procedures to obtain data from triangle grids tend to be more complex and consequently slower than the rectangle grid.

Example:

Input Samples and Isolines:

Output TIN:

It is accessible through:

PROCESSING → DTM PROCESSING → TIN GENERATION...

1. Select Input Layer(s)

Use combobox or

to select a isolines and/or samples layer. If you are not going to use both types of layer leave one blank, but one type should be selected.

If the selected layer does not have 3d information in its geometry, in the Quota Column combobox, select the attribute that contains the attribute to be used.

2. Inform Target Scale

Enter the wanted scale and click on the OK button. It will automatically calculate and suggest values for triangulation and line simplification. If needed user can adjust those values.

3. Select the algorithm to generate TIN

Delaunay
Smaller Angle

4. Inform the Minimum Edge Size

Enter the value in meters of the minimum size will be considered in the process.

5. Break Line

select Yes if interpolator will use break lines. In this case, it can be possible with a layer that contains break lines; if not informed system looks for break lines in the own numeric layer that contain the samples. If the option is No, the system will not consider break lines.

6. Line Simplification: data preprocessing phase values that are calculated initially from the defined scale of the layer. Parameters can be:

Isolines Tolerance: enter the value in meters.
Distance of isolines points: enter the value in meters.

7. Inform Output Parameters

Resolution X / Y : grid space.
Dimension C / L : number of lines and columns.
Note that these values are calculated as they are edited, when entering resolution the size of the grid is calculated and vice versa.

8. Set Output SRS

to select output layer SRS.

9. Inform the Output Repository by clicking on:

9.1.

to select the output directory and also inform the new layer name to store the result, or
9.2.

to select the Data Source and Inform the new Layer Name to store the aggregation result.

10. Click OK to perform the operation or Cancel to close the interface.