Low-level wk filters and handlers

s2_unprojection_filter(
  handler,
  projection = s2_projection_plate_carree(),
  tessellate_tol = Inf
)

s2_projection_filter(
  handler,
  projection = s2_projection_plate_carree(),
  tessellate_tol = Inf
)

s2_projection_plate_carree()

s2_projection_mercator()

Arguments

handler	A wk_handler object.
projection	One of `s2_projection_plate_carree()` or `s2_projection_mercator()`
tessellate_tol	An angle in radians. Points will not be added if a line segment is within this distance of a point.

Value

s2_unprojection_filter(), s2_projection_filter(): A new_wk_handler()
s2_projection_plate_carree(), s2_projection_mercator(): An external pointer to an S2 projection.

Examples

library(wk)

# simple conversion of individual coordinates *to* unit sphere
# space
wk_handle(
  wkt("LINESTRING (0 0, 0 45, -60 45)"),
  s2_unprojection_filter(wkt_format_handler(5))
)
#> [1] "LINESTRING Z (1 0 0, 0.70711 0 0.70711, 0.35355 -0.61237 0.70711)"

# simple conversion of individual coordinates *from* unit sphere
# space
wk_handle(
  wkt("LINESTRING Z (1 0 0, 0.7071 0 0.7071, 0.3536 -0.6124 0.7071)"),
  s2_projection_filter(wkt_format_handler(5))
)
#> [1] "LINESTRING (0 0, 0 45, -59.998 44.998)"

# use tessellate_tol to force points to be added to an edge
# unprojection will ensure an edge maintains its cartesian
# assumption when transformed to the unit sphere
# (i.e., what you probably want when importing a geography)
wk_handle(
  wkt("LINESTRING (0 0, 0 45, -60 45)"),
  s2_unprojection_filter(wkt_format_handler(5), tessellate_tol = 0.001)
)
#> [1] "LINESTRING Z (1 0 0, 0.70711 0 0.70711, 0.70559 -0.046247 0.70711, 0.70106 -0.092296 0.70711, 0.69352 -0.13795 0.70711, 0.68301 -0.18301 0.70711..."

# projection will ensure an edge maintains its geodesic
# assumption when transformed to projected space
# (i.e., what you probably want when exporting a geography)
wk_handle(
  wkt("LINESTRING Z (1 0 0, 0.7071 0 0.7071, 0.3536 -0.6124 0.7071)"),
  s2_projection_filter(wkt_format_handler(5), tessellate_tol = 0.001)
)
#> [1] "LINESTRING (0 0, 0 45, -3.4459 45.927, -7.0019 46.747, -10.66 47.453, -14.409 48.04..."