Detect water

Detects bodies of water (of a user-defined minimum size) within an elevation matrix.

detect_water(
  heightmap,
  zscale = 1,
  cutoff = 0.999,
  min_area = length(heightmap)/400,
  max_height = NULL,
  normalvectors = NULL,
  keep_groups = FALSE,
  progbar = FALSE
)

Arguments

heightmap

A two-dimensional matrix, where each entry in the matrix is the elevation at that point. All grid points are assumed to be evenly spaced. Alternatively, if heightmap is a logical matrix, each entry specifies whether that point is water or not.

zscale

Default 1. The ratio between the x and y spacing (which are assumed to be equal) and the z axis. For example, if the elevation levels are in units of 1 meter and the grid values are separated by 10 meters, zscale would be 10.

cutoff

Default 0.999. The lower limit of the z-component of the unit normal vector to be classified as water.

min_area

Default length(heightmap)/400. Minimum area (in units of the height matrix x and y spacing) to be considered a body of water.

max_height

Default NULL. If passed, this number will specify the maximum height a point can be considered to be water.

normalvectors

Default NULL. Pre-computed array of normal vectors from the calculate_normal() function. Supplying this will speed up water detection.

keep_groups

Default FALSE. If TRUE, the matrix returned will retain the numbered grouping information.

progbar

Default FALSE. If TRUE, turns on progress bar.

Value

Matrix indicating whether water was detected at that point. 1 indicates water, 0 indicates no water.

Examples

library(magrittr)
#Here we even out a portion of the volcano dataset to simulate water:
island_volcano = volcano
island_volcano[island_volcano < mean(island_volcano)] = mean(island_volcano)

#Setting a minimum area avoids classifying small flat areas as water:
island_volcano %>%
 sphere_shade(texture="imhof3") %>%
 add_water(detect_water(island_volcano, min_area = 400),color="imhof3") %>%
 plot_map()