Forward face projection

Projects geographic coordinates onto a face of the solid, returning face index and planar coordinates (tx, ty).

Usage

hexify_forward(
  lon,
  lat,
  projection = c("isea", "fuller"),
  polyhedron = c("icosahedron", "octahedron", "tetrahedron")
)

Arguments

lon

Longitude in degrees

lat

Latitude in degrees

projection

Face projection: "isea" (Snyder's equal-area projection) or "fuller" (Fuller's projection, defined on the icosahedron only)

polyhedron

The solid: "icosahedron" (default), "octahedron" or "tetrahedron", in its default orientation. Snyder (1992) gives his equal-area projection for each; its angular distortion grows with the faces' size.

Value

Named numeric vector: c(face, tx, ty)

Details

tx and ty are normalized coordinates within the triangular face, typically in range [0, 1].

See also

Other projection: hexify_build_icosa(), hexify_face_centers(), hexify_forward_to_face(), hexify_inverse(), hexify_which_face()

Examples

result <- hexify_forward(16.37, 48.21)
# result["face"], result["icosa_triangle_x"], result["icosa_triangle_y"]
hexify_forward(16.37, 48.21, polyhedron = "tetrahedron")