elev_to_morphometry: Calculate derivatives from the Morphometry module

In loreabad6/terrain: Utility Functions for Terrain Derivatives Calculations

Calculate derivatives from the Morphometry module

Description

Calculate derivatives from the Morphometry module

Usage

elev_to_morphometry(
  elev_sgrd,
  out_dir,
  prefix = "",
  envir,
  ...,
  aspect = FALSE,
  ccros = FALSE,
  cgene = FALSE,
  clong = FALSE,
  cmaxi = FALSE,
  cmini = FALSE,
  cplan = FALSE,
  cprof = FALSE,
  cvidx = FALSE,
  ddgrd = FALSE,
  mbidx = FALSE,
  mdslp = FALSE,
  nrhgt = FALSE,
  slhgt = FALSE,
  slope = FALSE,
  sthgt = FALSE,
  textu = FALSE,
  tpidx = FALSE,
  tridx = FALSE,
  vldpt = FALSE,
  units = "degrees",
  extra_texture_scale = 10
)

Arguments

elev_sgrd	input, elevation raster data in SAGA format, can be created with elev_to_sgrd()
out_dir	output directory
prefix	character prefix for output filenames
envir	environment to get SAGA installation, can be set with init_saga()
...	ignored, check help page for possible outputs
aspect	Aspect: the compass direction that a slope faces. Boolean, defaults to FALSE
ccros	Crossectional Curvature: Boolean, defaults to FALSE
cgene	Curvature (General Curvature): Boolean, defaults to FALSE
clong	Longitudinal Curvature: Boolean, defaults to FALSE
cmaxi	Maximum Curvature: Boolean, defaults to FALSE
cmini	Minimum Curvature: Boolean, defaults to FALSE
cplan	Plan Curvature: Boolean, defaults to FALSE
cprof	Profile Curvature: Surface curvature in the direction of gradient Boolean, defaults to FALSE
cvidx	Convergence Index: Calculates an index of convergence/divergence regarding to overland flow. By its meaning it is similar to plan or horizontal curvature, but gives much smoother results. The calculation uses the aspects of surrounding cells, i.e. it looks to which degree surrounding cells point to the center cell. The result is given as percentages, negative values correspond to convergent, positive to divergent flow conditions. Minus 100 would be like a peak of a cone (a), plus 100 a pit (c), and 0 an even slope (b). Boolean, defaults to FALSE
ddgrd	Downslope distance gradient: describes wet areas by assuming water accumulation in flat areas is due to upslope, local and downslope topography. It is a quantitative estimation of the hydraulic gradient. Obtained by calculating the downhill distance when water loses a determined quantity of energy from precipitation. Boolean, defaults to FALSE
mbidx	Mass Balance Index: Negative MBI values represent areas of net deposition such as depressions and floodplains; positive MBI values represent areas of net erosion such as hillslopes, and MBI values close to zero indicate areas where there is a balance between erosion and deposition such as low slopes and plain areas. High positive MBI values occur at convex terrain forms, like upper slopes and crests, while lower MBI values are associated with valley areas and concave zones at lower slopes. Balanced MBI values close to zero can be found in midslope zones and mean a location of no net loss or net accumulation of material. Boolean, defaults to FALSE
mdslp	Midslope Position: Boolean, defaults to FALSE
nrhgt	Normalized Height: Boolean, defaults to FALSE
slhgt	Slope Height: Boolean, defaults to FALSE
slope	Slope gradient: Reflects the maximal rate of change of elevation values. Boolean, defaults to FALSE
sthgt	Standardized Height: Boolean, defaults to FALSE
textu	Texture: This parameter emphasizes fine versus coarse expression of topographic spacing, or “grain”… Texture is calculated by extracting grid cells (here, informally, “pits” and “peaks”) that outline the distribution of valleys and ridges. It is defined by both relief (feature frequency) and spacing in the horizontal. Each grid cell value represents the relative frequency (in percent) of the number of pits and peaks within a radius of ten cells (Iwahashi and Pike, 2007. pp.412-413). It should be noted that it is not clear that the relative frequency is actually a percentage. According to Iwahashi and Pike (2007, p.30), To ensure statistically robust classes, thresholds for subdividing the images are arbitrarily set at mean values of frequency distributions of the input variables. Boolean, defaults to FALSE
tpidx	Topographic Position Index: Measures the relative topographic position of the central point as the difference between the elevation at this point and the mean elevation within a predetermined neighbourhood. Using TPI, landscapes can be classified in slope position classes. TPI is only one of a vast array of morphometric properties based on neighbouring areas that can be useful in topographic and DEM analysis. Used for roughness determination. The lower the numbers are the lower areas in the landscape. The higher numbers are the higher areas in the landscape. Boolean, defaults to FALSE
tridx	Terrain Ruggedness Index: Quantitative measure of topographic heterogeneity by calculating the sum change in elevation between a grid cell and its eight neighbor grid cells. This tool works with absolute values by squaring the differences between the target and neighbor cells, then taking the square root. Concave and convex shape areas could have similar values. The value of this metric will vary as a function of the size and complexity of the terrain used in the analysis. The closer you are to 0 the less rugged the terrain likely is. The bigger the number is, e.g. 105, then the terrain is likely to be more rugged. Boolean, defaults to FALSE
vldpt	Valley Depth: Calculated as difference between the elevation and an interpolated ridge level. Ridge level interpolation uses the algorithm implemented in the 'Vertical Distance to Channel Network' tool. Boolean, defaults to FALSE
units	character, units for slope and aspect output
extra_texture_scale	integer, defines the scale for texture computation

References

Olaya, V. (2009). Basic land-surface parameters. In Developments in Soil Science (Vol. 33, Issue C). Elsevier Ltd. https://doi.org/10.1016/S0166-2481(08)00006-8

https://sourceforge.net/p/saga-gis/wiki/ta_morphometry_1/

loreabad6/terrain documentation built on July 6, 2023, 6:44 a.m.