Terrain

Components for analysing different elements of landform.

The associated model and definition that demonstrating the use of these components can be downloaded here. You will need to have installed the Groundhog plugin for the definition to work correctly.

Landform is more heterogeneous and complex than contour lines suggest. Seemingly-similar areas of terrain can possess quite distinct characteristics depending on relatively small variations in their grading and position within the wider landscape. Digital models of landscapes often obscure this variety and make it difficult to determine or apprehend these characteristics given the artificial manner in which they are rendered.

Groundhog provides a number of components for measuring particular characteristics of a given landform. However its worth noting that, as above, such tools for classifying topographic features are only as good as their underpinning 3D representations. Representing a landform as (say) either a Mesh or a Surface will create different trade-offs in the types of accuracy and detail offered.

Visualisations of slope analysis across a `Mesh`, showing each face's grade as a vector, fill, and label

Visualisations of slope analysis across a Mesh, showing each face’s grade as a vector, fill, and label

Philip Belesky, for http://groundhog.la

The slope analysis components operate by identifying the normals of each face within the (land)form and measuring those vectors against the Z-axis. This produces a measure of steepness that can be output as either an angle or percentile. Either output can then be filtered and visualised to assist in grading tasks that may need to ensure slopes stay within a particular range (say to ensure accessible circulation) or to highlight areas that are vulnerable to erosion or require stabilisation.

Mesh Slope
Component
Nickname
Slope
Panel
Terrain
Icon
Icon for the Slope component

Analyses the slope of a Mesh, outputting separated faces for coloring and the slope/grade

Mode Name ID Description Optional Type
Mesh M The terrain mesh MeshParameter
Mesh Faces F The sub mesh faces (for coloring) MeshParameter
Face Centers C The centers of each mesh face (for vector previews) PointParameter
Face Vectors V The direction to the lowest points of each face VectorParameter
Face Slopes ° A The slope of each mesh face, as the angle of inline NumberParameter
Face Slopes % P The slope of each mesh face, as a percentage NumberParameter
Face Slopes : P The slope of each mesh face, as the denominator of a ratio (i.e. 1:x) NumberParameter

The aspect analysis components operate in a similar fashion, but measure the faces’ normals relative to a specified vector. This vector defaults to the Y-axis (assuming this is the North direction) and so produces a measure of which direction a slope faces. This can be used to identify areas within the landform that have a particular aspect, e.g. those that are predominantly north-easterly, and help determine the micro-climates of different areas of the landscape (based on their different levels of solar insolation) or to determine their visibility relative to a given vantage point.

Mesh Aspect
Component
Nickname
Aspect
Panel
Terrain
Icon
Icon for the Aspect component

Analyses the aspect of a Mesh, outputting separated faces for coloring and the aspect

Mode Name ID Description Optional Type
Mesh M The terrain mesh MeshParameter
Aspect A Vector representing the direction to measure aspect against VectorParameter
Mesh Faces F The sub mesh faces (for coloring) MeshParameter
Face Centers C The centers of each mesh face (for vector previews) PointParameter
Face Aspects A The aspect of each mesh face (measured in degrees) NumberParameter

Note that each component calculates the specified values, but does not visualise them within the model itself. For visualisation purposes, you typically want to translate the raw outputs of the slope or aspect components into colors by using the Gradient component and then a Preview component that matches the list to each individual mesh face. The reference definition provided at the top of this page shows an example of this process and several other visualisation options.

Components are provided (as a convenience) for employing the same analytics on a Surface rather than a Mesh, although note that the former will be converted to the latter during the actual calculation.

Surface Slope
Component
Nickname
Slope
Panel
Terrain
Icon
Icon for the Slope component

Analyses the slope of a Surface, outputting separated faces for coloring and the slope/grade

Mode Name ID Description Optional Type
Surface S The terrain surface SurfaceParameter
Mesh Faces F The sub mesh faces (for coloring) MeshParameter
Face Centers C The centers of each mesh face (for vector previews) PointParameter
Face Vectors V The direction to the lowest points of each face VectorParameter
Face Slopes ° A The slope of each mesh face, as the angle of inline NumberParameter
Face Slopes % P The slope of each mesh face, as a percentage NumberParameter
Face Slopes : P The slope of each mesh face, as the denominator of a ratio (i.e. 1:x) NumberParameter
Surface Aspect
Component
Nickname
Aspect
Panel
Terrain
Icon
Icon for the Aspect component

Analyses the aspect of a Surface, outputting separated faces for coloring and the aspect

Mode Name ID Description Optional Type
Surface S The terrain surface SurfaceParameter
Aspect A Vector representing the direction to measure aspect against VectorParameter
Mesh Faces F The sub mesh faces (for coloring) MeshParameter
Face Centers C The centers of each mesh face (for vector previews) PointParameter
Face Aspects A The aspect of each mesh face (measured in degrees) NumberParameter

Coming Soon: further components that provide other metrics for assessing different terrain characteristics.