transform_xy() transforms geospatial x, y coordinates to a new
projection. The input points may optionally have z vertices (x, y, z) or
time values (x, y, z, t).
Wrapper for OGRCoordinateTransformation::Transform() in the GDAL Spatial
Reference SYstem C++ API.
Arguments
- pts
A data frame or numeric matrix containing geospatial point coordinates, or point geometries as a list of WKB raw vectors or character vector of WKT strings. If data frame or matrix, the number of columns must be either two (x, y), three (x, y, z) or four (x, y, z, t). May be also be given as a numeric vector for one point (xy, xyz, or xyzt).
- srs_from
Character string specifying the spatial reference system for
pts. May be in WKT format or any of the formats supported bysrs_to_wkt().- srs_to
Character string specifying the output spatial reference system. May be in WKT format or any of the formats supported by
srs_to_wkt().
Value
Numeric matrix of geospatial (x, y) coordinates in the projection
specified by srs_to (potentially also with z, or z and t columns).
Note
transform_xy() uses traditional GIS order for the input and output xy
(i.e., longitude/latitude ordered for geographic coordinates).
Examples
pt_file <- system.file("extdata/storml_pts.csv", package="gdalraster")
pts <- read.csv(pt_file)
print(pts)
#> id xcoord ycoord
#> 1 1 324650.9 5103344
#> 2 2 324171.0 5103034
#> 3 3 323533.4 5103329
#> 4 4 325220.0 5103508
#> 5 5 325703.1 5102377
#> 6 6 326297.8 5103924
#> 7 7 325520.4 5104146
#> 8 8 326247.7 5102506
#> 9 9 327711.7 5104476
#> 10 10 324181.7 5103901
# id, x, y in NAD83 / UTM zone 12N
# transform to NAD83 / CONUS Albers
transform_xy(pts = pts[, -1], srs_from = "EPSG:26912", srs_to = "EPSG:5070")
#> [,1] [,2]
#> [1,] -1330885 2684892
#> [2,] -1331408 2684660
#> [3,] -1331994 2685048
#> [4,] -1330297 2684967
#> [5,] -1329991 2683777
#> [6,] -1329167 2685212
#> [7,] -1329903 2685550
#> [8,] -1329432 2683821
#> [9,] -1327683 2685541
#> [10,] -1331265 2685514