rgdal (version 1.6-7)

CRS-class: Class "CRS" of coordinate reference system arguments

Description

Interface class to the PROJ.4 projection system. The class is defined as an empty stub accepting value NA in the sp package. If the rgdal package is available, then the class will permit spatial data to be associated with coordinate reference systems

Usage

checkCRSArgs_ng(uprojargs=NA_character_, SRS_string=NULL,
  get_source_if_boundcrs=TRUE)
compare_CRS(CRS1, CRS2)

Objects from the Class

Objects can be created by calls of the form CRS("projargs"), where "projargs" is a valid string of PROJ.4 arguments; the arguments must be entered exactly as in the PROJ.4 documentation, in particular there cannot be any white space in +<arg>=<value> strings, and successive such strings can only be separated by blanks. The initiation function calls the PROJ.4 library to verify the argument set against those known in the library, returning error messages where necessary. The complete argument set may be retrieved by examining the second list element returned by validObject("CRS object") to see which additional arguments the library will use (which assumptions it is making over and above submitted arguments). The function CRSargs() can be used to show the expanded argument list used by the PROJ.4 library.

Slots

projargs:

Object of class "character": projection arguments; the arguments must be entered exactly as in the PROJ.4 documentation, in particular there cannot be any white space in +<arg>=<value> strings, and successive such strings can only be separated by blanks.

Methods

show

signature(object = "CRS"): print projection arguments in object

Arguments

uprojargs

character string PROJ.4 projection arguments

SRS_string

default NULL, experimental in connection with adaptation to GDAL>=3/PROJ>=6; a valid WKT string or SRS definition such as "OGC:CRS84"

get_source_if_boundcrs

The presence of the +towgs84= key in a Proj4 string projargs= argument value may promote the output WKT2 CRS to BOUNDCRS for PROJ >= 6 and GDAL >= 3, which is a coordinate operation from the input datum to WGS84. This is often unfortunate, so a PROJ function is called through rgdal to retrieve the underlying source definition.

CRS1, CRS2

objects of class "CRS"

Author

Roger Bivand

References

https://proj.org/

Examples

library(sp)
data(meuse)
coordinates(meuse) <- c("x", "y")
proj4string(meuse) <- CRS("+init=epsg:28992")
CRSargs(CRS(proj4string(meuse)))
run <- new_proj_and_gdal()
if (run) {
c1 <- CRS(SRS_string="OGC:CRS84")
c2 <- CRS("+proj=longlat")
compare_CRS(c1, c2)
}
if (run) {
comment(c2) <- NULL
compare_CRS(c1, c2)
}