Creates a transformation object that transforms coordinates in a wk pipeline.
proj_trans_create(source_crs, target_crs, use_z = NA, use_m = NA)Source/Target CRS definition, coerced with wk::wk_crs_proj_definition()
Used to declare the output type. Use TRUE to
ensure the output has that dimension, FALSE to ensure it does not,
and NA to leave the dimension unchanged.
A PROJ transformation object
(trans <- proj_trans_create("EPSG:4326", "EPSG:3857"))
#> <proj_trans at 0x562ab060f460>
#> type: Concatenated Operation
#> id: pipeline
#> description: axis order change (2D) + Popular Visualisation Pseudo-Mercator
#> definition: proj=pipeline step proj=unitconvert xy_in=deg xy_out=rad step proj=webmerc lat_0=0 lon_0=0 x_0=0 y_0=0 ellps=WGS84
#> area_of_use:
#> name: World
#> bounds: [-180 -90 180 90]
#> source_crs:
#> type: Geographic 2D CRS
#> id: EPSG:4326
#> name: WGS 84
#> area_of_use:
#> name: World.
#> bounds: [-180 -90 180 90]
#> target_crs:
#> type: Projected CRS
#> id: EPSG:3857
#> name: WGS 84 / Pseudo-Mercator
#> area_of_use:
#> name: World between 85.06°S and 85.06°N.
#> bounds: [-180 -85.06 180 85.06]
wk::wk_transform(wk::xy(1:5, 1:5), trans)
#> <wk_xy[5]>
#> [1] (111319.5 111325.1) (222639.0 222684.2) (333958.5 334111.2)
#> [4] (445278.0 445640.1) (556597.5 557305.3)
library(wk)
(invtrans <- wk_trans_inverse(trans))
#> <proj_trans at 0x562ab00944b0>
#> type: Concatenated Operation
#> id: pipeline
#> description: axis order change (2D) + Popular Visualisation Pseudo-Mercator
#> definition: proj=pipeline step proj=unitconvert xy_in=deg xy_out=rad step proj=webmerc lat_0=0 lon_0=0 x_0=0 y_0=0 ellps=WGS84
#> area_of_use:
#> name: World
#> bounds: [-180 -90 180 90]
#> source_crs:
#> type: Projected CRS
#> id: EPSG:3857
#> name: WGS 84 / Pseudo-Mercator
#> area_of_use:
#> name: World between 85.06°S and 85.06°N.
#> bounds: [-180 -85.06 180 85.06]
#> target_crs:
#> type: Geographic 2D CRS
#> id: EPSG:4326
#> name: WGS 84
#> area_of_use:
#> name: World.
#> bounds: [-180 -90 180 90]
h <- 1852 * 60
## the stretch of Mercator to a square
wk::wk_transform(wk::xy(c(-h * 180, 0, h * 180), c(-h * 180,0, h * 180)), invtrans)
#> <wk_xy[3]>
#> [1] (-179.6774 -85.02322) ( 0.0000 0.00000) ( 179.6774 85.02322)