How to generate a triangular grid

See about the Triangular Grid in the SPRING

Generating a Triangular Grid :

  • activate, in the "Control Panel", the Information Layer that has the samples (contour lines and spot heights) for a grid generation;
  • click on DTM - Triangular Grid Generation ... in the main menu;
  • in Input - click on the representation that will originate the TIN: Sample (points and/or contour lines), Grid rectangular or triangular grid (TIN). In this SPRING version only the Sample option is available;
  • give the Output Layer name which will have the TIN. By "default" the system will present the active IL name;
  • click on Bounding Box... to generate a grid in a geographic area smaller than the active IL whole area. In this case the user has to provide a name for the new output IL (see more details about how to do this at change the bounding box);
  • select in Type: only the Delaunay triangulation, the Delaunay triangulation with the Smaller Angle modification between normals, or the Delauney triangulation with Contour Lines modification which do not intercept the triangulations edges (see description above);
  • inform if the interpolator will use breaking lines or not. If yes, give the IL name (thematic, cadastral or network) which has the breaking lines; if the name is not provided the system will search for breaking lines in the numerical IL which has the samples. If Not the system will not consider breaking lines;
  • at Lines Generalization there are values for the Data Pre-Processing step, which are initially computed from the scale defined for the active IL. It is possible to change the Contour Lines Tolerance (m), Distance Between Points of the Contour Lines (m) and Break Lines Tolerance (m) parameters;
  • define in Triangulation the Minimum Edge Size(m) value;
  • click on Apply to confirm the Triangular grid generation.

NOTE: After generating a triangular grid in an IL from the numerical model, it will be available in the "Control Panel". In order to see the grid just activate the IL which has the grid and select the TIN representation in the panel.

The result of the Delauney triangulation is presented in the figures below: in (A) it is possible to see the samples (contour lines and height spots) in a 1:25,000 chart. In (B) and (C) triangular grids generated with different simplification parameters: Contour Lines Tolerance (m) = 10 and 5, Distance between Points of the Contour Lines (m) = 200 and 100 and Break Lines Tolerance (m) = 10 and 5, respectively. Notice that the triangle density generated in (C) is practically twice, as a function of the parameters reduction presented above, and also the space required to store it is larger.

It is recommended that the user perform some tests to find what triangulation is better adapted to the working scale and its own modeling.

A-)mnt_amostra.gif - 7087 Bytes

B-)mnt_amostra_tin.gif - 10832 Bytes    C-)mnt_amostra_tin2.gif - 11144 Bytes


NOTE: If desired, the user can change the visual aspects for the triangular grid representation; click on Edit - Information Layer in the main menu, select the TIN representation in the numerical IL and click on Visual... to make the changes.


See also:
DTM Products in the SPRING - What are they and how to execute them?