Terrain

Components for quantifying different elements of topographic form.

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 properly.

Topography is heterogeneous in a more complex manner than contours or a 3D visualisation often suggest. Different and seemingly-similar areas of landform can posses quite distinct characteristics depending on relatively small variations in their grading and wider position within the landscape. 3D models in particular often make it difficult to determine or apprehend these characteristics of digital terrain models 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 landform as (say) either a Mesh or a Surface has different trade-offs in terms of the different types of accuracy and level of detailed 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 component operates by identifying the normals of each face within the form and measuring those against the Z-axis to produce a measure of steepness that can be output as either an angle or percentile. This 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

Nickname
Slope
Panel
Terrain
Icon

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 an angle NumberParameter
Face Slopes % P The slope of each mesh face, as a percentile NumberParameter

The aspect analysis component operates in a similar fashion but measures the faces’ normals relative to a specified vector. This vector defaults to the Y-axis (assuming that 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, such as those that are predominantly north-easterly. This can be used to 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

Nickname
Aspect
Panel
Terrain
Icon

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

Each component calculates the specified values but does not visualise them in the model itself. For visualisation purposes you will typically want to assign the range of slope or aspect values to a colour using the Gradient component then use a Preview component to apply these colours 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 calculation.

Surface Slope

Nickname
Slope
Panel
Terrain
Icon

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 an angle NumberParameter
Face Slopes % P The slope of each mesh face, as a percentile NumberParameter

Surface Aspect

Nickname
Aspect
Panel
Terrain
Icon

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.