CRS-class               package:rgdal               R Documentation

_C_l_a_s_s "_C_R_S" _o_f _c_o_o_r_d_i_n_a_t_e _r_e_f_e_r_e_n_c_e _s_y_s_t_e_m _a_r_g_u_m_e_n_t_s

_D_e_s_c_r_i_p_t_i_o_n:

     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

_O_b_j_e_c_t_s _f_r_o_m _t_h_e _C_l_a_s_s:

     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.

_S_l_o_t_s:

     '_p_r_o_j_a_r_g_s': 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. 

_M_e_t_h_o_d_s:

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

_N_o_t_e:

     Lists of projections may be seen by using the programs installed
     with the PROJ.4 library, in particular proj and cs2cs; with the
     latter, -lp lists projections, -le ellipsoids, -lu units, and -ld
     datum(s) known to the installed software. These are added to in
     successive releases, so tracking the website or compiling and
     installing the most recent revisions will give the greatest
     choice. On occasion, ellipsoid parameters may be passed through
     directly. Tracing projection arguments is easier now than before
     the mass ownership of GPS receivers raised the issue of matching
     coordinates from different argument sets (GPS output and paper
     map, for example).

_A_u_t_h_o_r(_s):

     Roger Bivand Roger.Bivand@nhh.no

_R_e_f_e_r_e_n_c_e_s:

     <URL: http://www.remotesensing.org/proj/>

_E_x_a_m_p_l_e_s:

     CRSargs(CRS("+proj=longlat +datum=NAD27"))
     CRSargs(CRS("+init=epsg:4267"))
     CRSargs(CRS("+init=epsg:26978"))
     CRSargs(CRS("+proj=stere +lat_0=52.15616055555555 +lon_0=5.38763888888889 +k=0.999908 +x_0=155000 +y_0=463000 +ellps=bessel +units=m"))
     CRSargs(CRS("+init=epsg:28992"))

