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-)
B-) C-)
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?
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