CRS-class {sp} | R Documentation

## 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 spproj package is available, then the class will permit spatial data to be associated with coordinate reference systems. 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.

### 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 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

### Methods

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

### Author(s)

Roger Bivand Roger.Bivand@nhh.no

### References

http://www.remotesensing.org/proj/

### Examples

[Package sp version 0.7-12 Index]