Evaluation of a digital terrain model:
Also, it is of interest the adequate representation of the forms of the terrain, that allows, the hydrological, geomorphological, climatic modeling, among others.
Digital terrain model in QGIS 3
The TIN method accepts different input vector entities, each influencing the triangulation differently:
- Elevation points.
- Structure lines: continuous lines that add information to the surface.
- Rupture lines: produce marked changes on the surface, for example to represent rivers, roads, coastlines.
Generation of a DEM of a small surface of steep relief within an agricultural farm.
To access the interpolation tools go to Process Menu > Process Toolbox, in the Panel select the Interpolation tab, then TIN Interpolation.
Digital model with elevation points
To compare the effect of introducing break lines, interpolation is first generated using elevation points extracted from the contour lines.
QGIS 3 offers two methods of generating TIN, Linear and Clough-Toucher, the second produces a smoother surface.
On the Extension tab click on the corner button > Use Canvas Layer Extension.
For more details on how to adjust pixel dimensions refer to the Spatial Interpolation article in QGIS 3.
Finally you can define the output files.
In Interpolated the name and location of the surface
Then in Triangulation the vector with the network of triangles.
Digital model with breaking points and lines
Again, deploy the TIN interpolation tool and configure the layers.
Enter the Points layer in the same way as above.
Then select in the Vector Layer tab > contour lines and in Attribute the Elevation field, add it to the list, in Type > Break Lines.
Then, for the Shelves layer select the option “Use z coordinates for interpolation“, in Type > Structure Line.
For the Hydro layer select the option “Use z coordinates for interpolation”, in Type > Break Line.
Configure the other options in the same way as above.
Finally, compare both surfaces.