Map tree stems over topography — plot

plot_topo() draws individual trees or stems over a topographic backdrop for ForestGEO-style and similar plot inventories (Wanang and other large forest dynamics plots). Points use local projected coordinates in metres (gx, gy) or geographic lon/lat. The backdrop can be contour lines, a DEM / hillshade raster, or both. Colour by species or size (DBH), and optionally draw the plot boundary.

Expected columns for a ForestGEO-like table: plot, treeID, stemID, gx, gy (metres from the plot origin), dbh, species, status. Geographic inventories may use lon / lat instead of gx / gy.

Pass your own stem inventory. geo_example_stems() is simulated test data for checking code, not a real plot, so do not publish maps drawn from it.

Usage

plot_topo(
  data,
  x = "gx",
  y = "gy",
  lon = NULL,
  lat = NULL,
  colour = NULL,
  size = NULL,
  dem = NULL,
  boundary = NULL,
  contours = TRUE,
  hillshade = TRUE,
  contour_breaks = NULL,
  basemap = "none",
  palette = c("okabe_ito", "grey"),
  point_alpha = 0.85
)

Arguments

data: A data frame of stems/trees, or an sf object.
x, y: <data-masking> Local metre columns (defaults gx, gy). Ignored when lon/lat are set or data is sf.
lon, lat: <data-masking> Optional geographic coordinates. When supplied, they override x/y.
colour: <data-masking> Grouping column (species, status) or a continuous size such as DBH.
size: <data-masking> Optional column mapped to point size (typically dbh). When NULL and dbh exists, DBH is used.
dem: Optional terra::SpatRaster elevation surface for hillshade and/or contours. In local metre coordinates the raster should use the same origin as gx/gy.
boundary: Optional sf polygon of the plot boundary, or a numeric bbox c(xmin, ymin, xmax, ymax).
contours: Draw contour lines from dem?
hillshade: Draw a hillshade backdrop from dem?
contour_breaks: Contour interval, or a vector of breaks. When NULL, pretty breaks are chosen.
basemap: Passed to geo_basemap() when using lon/lat (for example "coast"). Ignored for local metre coordinates.
palette: Discrete palette when colour is categorical.
point_alpha: Point opacity.

Value

A ggplot object.

Examples

stems <- geo_example_stems()
dem <- geo_example_dem()
plot_topo(stems, colour = species, size = dbh, dem = dem, boundary = c(0, 0, 100, 100))