xdem.DEM.get_terrain_attribute

DEM.get_terrain_attribute(attribute, **kwargs)

Derive one or multiple terrain attributes from a DEM. The attributes are based on:

• Slope, aspect, hillshade (first method) from Horn (1981), http://dx.doi.org/10.1109/PROC.1981.11918,

• Slope, aspect, hillshade (second method), and terrain curvatures from Zevenbergen and Thorne (1987),

  http://dx.doi.org/10.1002/esp.3290120107, with curvature expanded in Moore et al. (1991),

• Curvatures (profile, tangential, planform, flowline, max, min) following the methods outlined

  in Minár et al. (2020), https://doi.org/10.1016/j.earscirev.2020.103414,

• Topographic Position Index from Weiss (2001), http://www.jennessent.com/downloads/TPI-poster-TNC_18x22.pdf.

• Terrain Ruggedness Index (topography) from Riley et al. (1999),

  http://download.osgeo.org/qgis/doc/reference-docs/Terrain_Ruggedness_Index.pdf.

• Terrain Ruggedness Index (bathymetry) from Wilson et al. (2007), http://dx.doi.org/10.1080/01490410701295962.

• Roughness from Dartnell (2000), thesis referenced in Wilson et al. (2007) above.

• Rugosity from Jenness (2004), https://doi.org/10.2193/0091-7648(2004)032[0829:CLSAFD]2.0.CO;2.

• Fractal roughness from Taud et Parrot (2005), https://doi.org/10.4000/geomorphologie.622.

Aspect and hillshade are derived using the slope, and thus depend on the same method. More details on the equations in the functions get_quadric_coefficients() and get_windowed_indexes().

This function can be run out-of-memory in multiprocessing by passing a Multiproc config argument.

Attributes:

• ‘slope’: The slope in degrees or radians (degs: 0=flat, 90=vertical). Default method: “Horn”.

• ‘aspect’: The slope aspect in degrees or radians (degs: 0=N, 90=E, 180=S, 270=W).

• ‘hillshade’: The shaded slope in relation to its aspect.

• ‘curvature’: The second derivative of elevation (the rate of slope change per pixel), multiplied by 100.

• ‘profile_curvature’: The curvature of a normal section having a common tangent line with a steepest slope,

  multiplied by 100.

• ‘tangential_curvature’: The curvature perpendicular to the profile curvature, multiplied by 100.

• ‘planform_curvature’: The curvature of a projected contour line, multiplied by 100.

• ‘flowline_curvature’: The curvature of a projected slope line, multiplied by 100.

• ‘max_curvature’: The maximal (geometric) or maximum (directional derivative) curvature at a point in any

  direction, multiplied by 100.

• ‘min_curvature’: The minimal (geometric) or minimum (directional derivative) curvature at a point in any

  direction, multiplied by 100.

• ‘surface_fit’: A quadric surface fit for each individual pixel.

• ‘topographic_position_index’: The topographic position index defined by a difference to the average of

  neighbouring pixels.

• ‘terrain_ruggedness_index’: The terrain ruggedness index. For topography, defined by the squareroot of squared

  differences to neighbouring pixels. For bathymetry, defined by the mean absolute difference to neighbouring pixels. Default method: “Riley” (topography).

• ‘roughness’: The roughness, i.e. maximum difference between neighbouring pixels.

• ‘rugosity’: The rugosity, i.e. difference between real and planimetric surface area.

• ‘fractal_roughness’: The roughness based on a volume box-counting estimate of the fractal dimension.

• ‘texture_shading’: Texture shaded relief using fractional Laplacian operator to enhance terrain texture and

  fine-scale topographic features.

Parameters:

• attribute (str | list[str]) – Terrain attribute(s) to calculate.

• degrees – Whether to convert radians to degrees.

• hillshade_altitude – Shading altitude in degrees (0-90°). 90° is straight from above.

• hillshade_azimuth – Shading azimuth in degrees (0-360°) going clockwise, starting from north.

• hillshade_z_factor – Vertical exaggeration factor.

• slope_method – Deprecated. Use surface_fit instead. Accepts “Horn” or “ZevenbergThorne”.

• surface_fit – Surface fit method to use for slope, aspect, hillshade and curvatures: “Horn”, “ZevenbergThorne” or “Florinsky”.

• curv_method – Method to calculate the curvatures: “geometric” or “directional”.

• tri_method – Method to calculate the Terrain Ruggedness Index: “Riley” (topography) or “Wilson” (bathymetry).

• window_size – Window size for windowed attributes (TPI, TRI, roughnesses, rugosity).

• engine – Engine to use for computing the attributes, windowed and surface fit attributes all support “scipy” or “numba”.

• out_dtype – Output dtype of the terrain attributes, can only be a floating type. Defaults to that of the input DEM if floating type or to float32 if integer type.

• mp_config – Multiprocessing configuration, run the function in multiprocessing if not None.

Raises:

ValueError – If the inputs are poorly formatted or are invalid.

Return type:

TypeVar(RasterType, bound= Raster) | list[TypeVar(RasterType, bound= Raster)]