Tissot indicatrices — viz_tissot • geovizr

The viz_tissot function draws Tissot circles to visualize projection distortions on a map.

Usage

viz_tissot(
  map,
  id = NULL,
  step = 20,
  fill = "red",
  stroke = "white",
  strokeOpacity = 0.5,
  ...
)

Arguments

map: A geovizr map object created using viz_create().
id: character. Optional. Unique layer id.
step: numeric. Optional. Step between circles (default 20).
fill: character. Optional. Fill color (default "red").
stroke: character. Optional. Stroke color (default "white").
strokeOpacity: numeric. Optional. Stroke opacity (default 0.5).
...: Additional SVG attributes (strokeDasharray, strokeWidth, opacity, strokeLinecap...).

Value

A modified `geoviz` map object with a new layer added. Rendering is performed using viz_render().

Examples

library(sf)
world <- st_read(
  system.file("gpkg/world.gpkg", package = "geovizr"),
  quiet = TRUE
)

viz_create(projection = "Polar", background = "white") |>
  viz_path(datum = world, fill = "#f1f3f5") |>
  viz_tissot(fill = "#38896F") |>
  viz_render()