make_shade function

Compute Hill Shade

Compute hill shade from a digital elevation model. A hill shade layer is often used as a backdrop on top of which another, semi-transparent, layer is drawn.

make_shade(
  x,
  scale = 2,
  neighbors = 8,
  angle = 40,
  direction = 270,
  normalize = TRUE
)

Arguments

• x: 'SpatRaster' object. Spatial raster of land-surface elevations, such as the dem dataset.
• scale: 'numeric' number. Scaling factor used to convert the elevation values. The default value is 2.
• neighbors: 'numeric' count. Number of neighboring cells to use to compute slope or aspect with. Either 8 (queen case) or 4 (rook case).
• angle: 'numeric' number. The sun's angle of elevation above the horizon, ranges from 0 to 90 degrees. A value of 0 degrees indicates that the sun is on the horizon. A value of 90 degrees indicates that the sun is directly overhead. Default is a 40 degree angle.
• direction: 'numeric' number. Direction (azimuth) angle of the light source (sun), in degrees. An direction of 0 degrees indicates north, east is 90 degrees, south is 180 degrees, and west is 270 degrees (default).
• normalize: 'logical' flag. Whether to set values below zero to zero and results normalized between 0 and 1.

Returns

Spatial raster of hill shade values.

Examples

elevation <- terra::unwrap(dem)
hillshade <- make_shade(elevation)
terra::plot(hillshade,
  col = inlcolor::get_colors(
    n = 256,
    scheme = "grayC"
  ),
  mar = c(2, 2, 1, 4),
  legend = FALSE
)
terra::plot(elevation,
  col = inlcolor::get_colors(
    n = 256,
    scheme = "dem2",
    alpha = 0.7,
    bias = 0.9
  ),
  add = TRUE
)

Author(s)

J.C. Fisher, U.S. Geological Survey, Idaho Water Science Center