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