fm_crs_plot: Plot CRS and fm_crs objects

In fmesher: Triangle Meshes and Related Geometry Tools

Plot CRS and fm_crs objects

Description

Plot the outline of a crs or fm_crs() projection, with optional graticules (transformed parallels and meridians) and Tissot indicatrices.

Usage

fm_crs_plot(
  x,
  xlim = NULL,
  ylim = NULL,
  outline = TRUE,
  graticule = c(15, 15, 45),
  tissot = c(30, 30, 30),
  asp = 1,
  add = FALSE,
  eps = 0.05,
  ...
)

fm_crs_graticule(
  x,
  by = c(15, 15, 45),
  add = FALSE,
  do.plot = TRUE,
  eps = 0.05,
  ...
)

fm_crs_tissot(
  x,
  by = c(30, 30, 30),
  add = FALSE,
  do.plot = TRUE,
  eps = 0.05,
  diff.eps = 0.01,
  ...
)

Arguments

x	A crs or fm_crs() object.
xlim	Optional x-axis limits.
ylim	Optional y-axis limits.
outline	Logical, if TRUE, draw the outline of the projection.
graticule	Vector of length at most 3, to plot meridians with spacing graticule[1] degrees and parallels with spacing graticule[2] degrees. graticule[3] optionally specifies the spacing above and below the first and last parallel. When graticule[1]==0 no meridians are drawn, and when graticule[2]==0 no parallels are drawn. Use graticule=NULL to skip drawing a graticule.
tissot	Vector of length at most 3, to plot Tissot's indicatrices with spacing tissot[1] degrees and parallels with spacing tissot[2] degrees. tissot[3] specifices a scaling factor. Use tissot=NULL to skip drawing a Tissot's indicatrices.
asp	The aspect ratio for the plot, default 1.
add	If TRUE, add the projecton plot to an existing plot.
eps	Clipping tolerance for rudimentary boundary clipping
...	Additional arguments passed on to the internal calls to plot and lines.
by	The spacing between ⁠(long, lat, long_at_poles)⁠ graticules/indicatrices, see the graticule and tissot arguments.
do.plot	logical; If TRUE, do plotting
diff.eps	Pre-scaling

Value

NULL, invisibly

Functions

• fm_crs_graticule(): Constructs graticule information for a given CRS or fm_crs() and optionally plots the graticules. Returns a list with two elements, meridians and parallels, which are SpatialLines objects.

• fm_crs_tissot(): Constructs Tissot indicatrix information for a given CRS or fm_crs() and optionally plots the indicatrices. Returns a list with one element, tissot, which is a SpatialLines object.

Author(s)

Finn Lindgren [e-mail]

See Also

fm_crs()

Examples

if (require("sf") && require("sp")) {
  for (projtype in c(
    "longlat_norm",
    "lambert_norm",
    "mollweide_norm",
    "hammer_norm"
  )) {
    fm_crs_plot(fm_crs(projtype), main = projtype)
  }
}

if (require("sf") && require("sp")) {
  oblique <- c(0, 45, 45, 0)
  for (projtype in c(
    "longlat_norm",
    "lambert_norm",
    "mollweide_norm",
    "hammer_norm"
  )) {
    fm_crs_plot(
      fm_crs(projtype, oblique = oblique),
      main = paste("oblique", projtype)
    )
  }
}

fmesher documentation built on April 3, 2025, 7:45 p.m.