prj_to_epsg <- function(prj) {
require(sp)
require(httr)
require(jsonlite)
res <- GET("http://prj2epsg.org/search.json",
query=list(exact=TRUE,
error=TRUE,
mode="wkt",
terms=prj))
# one shld prbly do more error checking than this
stop_for_status(res)
dat <- fromJSON(content(res, as="text", flatten=TRUE))
# NOTE: there could be more in dat$codes if prj was ambiguous
CRS(paste0("+init=epsg:", dat$codes[1, "code"]))
}
prj <- paste0(readLines("110m_admin_1_states_provinces_shp.prj"))
prj_to_epsg(prj)
## CRS arguments:
## +init=epsg:4326 +proj=longlat +datum=WGS84 +no_defs +ellps=WGS84
## +towgs84=0,0,0
prj_1 <- 'PROJCS["Transverse_Mercator",
GEOGCS["GCS_OSGB 1936",
DATUM["D_OSGB_1936",
SPHEROID["Airy_1830",6377563.396,299.3249646]],
PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],
PROJECTION["Transverse_Mercator"],
PARAMETER["latitude_of_origin",49],
PARAMETER["central_meridian",-2],
PARAMETER["scale_factor",0.9996012717],
PARAMETER["false_easting",400000],
PARAMETER["false_northing",-100000],
UNIT["Meter",1]]'
prj_to_epsg(prj_1)
## CRS arguments:
## +init=epsg:27700 +proj=tmerc +lat_0=49 +lon_0=-2 +k=0.9996012717
## +x_0=400000 +y_0=-100000 +datum=OSGB36 +units=m +no_defs +ellps=airy
## +towgs84=446.448,-125.157,542.060,0.1502,0.2470,0.8421,-20.4894
On Tue, Jan 5, 2016 at 5:09 AM, Michael Sumner <mdsumner at gmail.com> wrote:
Hello, is there any R-level way to convert a WKT/PRJ *coordinate system*
string to PROJ.4 used by sp/rgdal?
(Previously I've written out to SHP/PRJ, and read back in with rgdal,