make_shade {inldata}

Compute Hill Shade

Description

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.

Usage

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.

Value

Spatial raster of hill shade values.

Author(s)

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

Examples

elevation <- terra::unwrap(dem)
hillshade <- make_shade(elevation)
print(hillshade)

col <- inlcolor::get_colors(n = 256, scheme = "grayC")
mar <- c(2, 2, 1, 4)
terra::plot(hillshade, col = col, mar = mar)

terra::plot(hillshade, col = col, mar = mar, legend = FALSE)
terra::plot(elevation,
  col = inlcolor::get_colors(
    n = 256,
    scheme = "dem2",
    alpha = 0.7,
    bias = 0.9
  ),
  add = TRUE
)