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== Terrain analysis in GRASS GIS ==

GRASS GIS offers an enormous range of methods and tools for terrain analysis.

(see also: [[Geomorphometry]] and [[Hydrological Sciences]])

=== Accumulation ===

* {{AddonCmd|r.accumulate}} addon module: Calculates weighted flow accumulation, subwatersheds, stream networks, and longest flow paths using a flow direction map.

=== Analytical Hillshading ===

* {{AddonCmd|r.shaded.pca}} addon module: Creates relief shades from various directions and combines them into RGB composition

=== Aspect ===

See: {{cmd|r.slope.aspect}}: Generates raster maps of slope, aspect, curvatures and partial derivatives from an elevation raster map

=== Basins ===

* {{AddonCmd|r.basin}} addon module: morphometric characterization of river basins
* {{cmd|r.basin.fill}}: Generates watershed subbasins raster map
* {{AddonCmd|r.valley.bottom}} addon module: Calculation of Multi-resolution Valley Bottom Flatness (MrVBF) index
* {{cmd|r.watershed}}: Determines watersheds

=== Catchment Area ===

* {{AddonCmd|r.catchment}} addon module: Creates a raster buffer of specified area around vector points using cost distances using {{cmd|r.walk}}

=== Channel Network Base Level ===

See list in [[Hydrological Sciences]]

=== Channel Network Distance ===

See list in [[Hydrological Sciences]]

=== Closed Depressions ===

* {{cmd|r.fill.dir}}: Filters and generates a depressionless elevation map and a flow direction map from a given elevation raster map

=== Contours ===

* {{cmd|r.contour}}: Produces a vector map of specified contours from a raster map

=== Convergence Index ===

* {{AddonCmd|r.convergence}} addon module: Calculate convergence index

=== Curvatures ===

* {{cmd|r.slope.aspect}}: Generates raster maps of slope, aspect, curvatures and partial derivatives from an elevation raster map

=== Flooding ===

* {{cmd|r.lake}}: Fills lake at given point to given level

=== Flow and lines ===

* {{cmd|r.flow}}: Computes flow-lines, flow-path lengths, and flow-accumulation (contributing areas)
* {{AddonCmd|r.accumulate}} addon module: Calculates weighted flow accumulation, subwatersheds, stream networks, and longest flow paths using a flow direction map.
* {{cmd|r.terraflow}}: Performs flow computation for massive grids

=== Fractal surfaces ===

* {{cmd|r.surf.fractal}}: Creates a fractal surface of a given fractal dimension

=== Habitats and terrain ===

* {{AddonCmd|v.habitat.dem}} addon module: Calculates DEM derived characteristics of habitats

=== Landscape evolution ===

* {{AddonCmd|r.sim.terrain}} addon module: Dynamic landscape evolution model

=== Local relief model ===

* {{AddonCmd|r.local.relief}} addon module: Creates a local relief model from elevation map

=== LS-Factor ===

* {{cmd|r.watershed}}: Calculates hydrological parameters and RUSLE factors

=== Multi-resolution Valley Bottom Flatness (MrVBF) index ===

* {{AddonCmd|r.valley.bottom}} addon module: Calculation of Multi-resolution Valley Bottom Flatness (MrVBF) index

=== Northerness, easterness ===

* {{AddonCmd|r.northerness.easterness}} addon module: Calculation of northerness, easterness and the interaction between northerness and slope

=== Random surfaces ===

* {{cmd|r.random.surface}}: Generates random surface(s) with spatial dependence
* {{cmd|r.surf.contour}}: Generates surface raster map from rasterized contours
* {{cmd|r.surf.fractal}}: Creates a fractal surface of a given fractal dimension
* {{cmd|r.surf.gauss}}: Generates a raster map using gaussian random number generator
* {{cmd|r.surf.idw}}: Provides surface interpolation from raster point data by Inverse Distance Squared Weighting
* {{cmd|r.surf.random}}: Produces a raster surface map of uniform random deviates with defined range

=== Shaded relief map ===

* {{cmd|r.relief}}: Creates shaded relief map from an elevation map (DEM)

=== Slope ===

* {{cmd|r.slope.aspect}}: Generates raster maps of slope, aspect, curvatures and partial derivatives from an elevation raster map
* {{AddonCmd|r.slope.direction}} addon module: Calculates slope following a direction raster

=== Stream channels ===

* {{cmd|r.carve}}: Generates stream channels
* see list in [[Hydrological Sciences]]

=== Surface roughness ===

* {{AddonCmd|r.roughness.vector}} addon module: Calculates surface roughness in a moving-window, as the orientation of vectors normal to surface planes.

=== Terrain classification ===

* {{AddonCmd|r.terrain.texture}} addon module: Unsupervised nested-means algorithm for terrain classification

=== Terrain forms (geomorphons) ===

* {{cmd|r.geomorphon}}: Calculates geomorphons (terrain forms) and associated geometry using machine vision approach

=== Topographic Position Index ===

* {{AddonCmd|r.tpi}} addon module: Calculates the multiscale topographic position index

=== Topographic Ruggedness Index ===

* {{AddonCmd|r.tri}} addon module: Computes the Terrain Ruggedness Index

=== Topographic Wetness Index ===

See: {{cmd|r.topidx}}: Creates a topographic index (wetness index) raster map from an elevation raster map

=== Vector Ruggedness Measure ===

* {{AddonCmd|r.vector.ruggedness}} addon module: Vector Ruggedness Measure

=== Watersheds ===

* {{cmd|r.watershed}}: Calculates hydrological parameters and RUSLE factors
* {{cmd|r.basin.fill}}: Generates watershed subbasins raster map

=== Valley Depth ===

* {{AddonCmd|r.valley.bottom}} addon module: Calculation of Multi-resolution Valley Bottom Flatness (MrVBF) index

=== Viewshed ===

* {{cmd|r.viewshed}}: Computes the viewshed of a point on an elevation raster map
* {{AddonCmd|r.viewshed.cva}} addon module: Undertakes a "cumulative viewshed analysis" using a vector points map as input "viewing" locations, using r.viewshed to calculate the individual viewsheds
* {{AddonCmd|r.viewshed.exposure}} addon module: Visual exposure to defined exposure source

== See also ==

* [[Introduction to GRASS GIS with terrain analysis examples]]
* [https://baharmon.github.io/terrain-analysis-in-grass Terrain Analysis in GRASS GIS]: A tutorial on terrain analysis in GRASS GIS
** Related video: https://vimeo.com/440840699

[[Category: Applications]]
[[Category: Terrain]]

Terrain analysis - Revision history

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