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 grid generation, making possible to model a terrain surface keeping surface geomorphic shapes.
Source: (SPRING 5.3, 2012).
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 characteristic 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 procedure to obtain data from triangle grids tend to be more complex and consequently slower than the rectangle grid.
Select DIGITAL TERRAIN MODEL → GENERATE TIN in the main menu.
Isolines Layer Tab:
Layer Name: Select the layer from the list.
Quota column: select one of the available options.
or
Samples Layer:
Layer Name: Select the layer from the list.
Quota column: select one of the available options.
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.
Triangulation:
Type: select between Delaunay or Smaller Angle.
Minimum Edge Size: enter the value in meters of the minimum size that will be considered in the process.
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 Not, the system will not consider break lines.
Line Simplification: data preprocessing phase values that are calculated initially from the defined scale of the layer. Parameters can be:
Isoline Tolerance: enter the value in meters.
Distance of isolines points: enter the value in meters.
Output Parameters:
Repository: Click
on the icon
to save the result in a shape file or click on the icon
to save it in a data source.
Layer Name: enter the name of the resulting image.
Click on the OK button.