r.poly(1)		      Grass User's Manual		     r.poly(1)



NNAAMMEE
       rr..ppoollyy  - Extracts area edges from a raster map layer and converts data
       to GRASS vector format.
       _(_G_R_A_S_S Raster Program)

SSYYNNOOPPSSIISS
       rr..ppoollyy
       rr..ppoollyy hheellpp
       rr..ppoollyy [--llccbb] iinnppuutt==_n_a_m_e oouuttppuutt==_n_a_m_e

DDEESSCCRRIIPPTTIIOONN
       _r_._p_o_l_y scans the named iinnppuutt raster map layer, extracts area edge  fea-
       tures  from it, converts data to GRASS vector format, and smoothes vec-
       tors.


       _r_._p_o_l_y first traces the perimeter of each unique area in the raster map
       layer  and creates vector data to represent it.	The cell category val-
       ues for the raster map layer will be used to create attribute  informa-
       tion for the resultant vector area edge data.


       A  true vector tracing of the area edges might appear blocky, since the
       vectors outline the edges of raster data that are stored in rectangular
       cells.	To  produce  a	better-looking vector map, _r_._p_o_l_y smoothes the
       corners of the vector data as they are being extracted. At each	change
       in  direction (i.e., each corner), the two midpoints of the corner cell
       (half the cell's height and width) are taken, and the line segment con-
       necting	them  is  used	to outline this corner in the resultant vector
       file.  (The cell's cornermost node is  ignored.)  Because  vectors  are
       smoothed  by  this program, the resulting vector map will not be "true"
       to the raster map from which it was created.  The user should check the
       resolution of the geographic region (and the original data) to estimate
       the possible error introduced by smoothing.

OOPPTTIIOONNSS
       The user can run this  program  either  non-interactively  or  interac-
       tively.	 The  program will be run non-interactively if the user speci-
       fies program arguments and flag settings on the command line using  the
       form: rr..ppoollyy [--llccbb] iinnppuutt==_n_a_m_e oouuttppuutt==_n_a_m_e

       Alternately,  the user can simply type rr..ppoollyy on the command line with-
       out program arguments. In this case, the  user  will  be  prompted  for
       parameter  values  and  flag  settings  using the standard GRASS _p_a_r_s_e_r
       interface.

   FFllaaggss::
       --ll     Smooth corners.

       --cc     Output values as category labels

       --bb     Output only area borders as vector lines


   PPaarraammeetteerrss::
       iinnppuutt==_n_a_m_e
	      Use the existing raster map _n_a_m_e as input.

       oouuttppuutt==_n_a_m_e
	      Set the new vector output file name to _n_a_m_e.


NNOOTTEESS
       _r_._p_o_l_y extracts only area edges from the named raster input  file.   If
       the  raster  file contains other data (i.e., line edges, or point data)
       the output may be wrong. Using _-_b the area borders (vector  line  type)
       are written instead of the areas (vector area type). This may be useful
       for buffering of area borders and other analysis.


       The user must run _v_._s_u_p_p_o_r_t on the resultant file to build  the	needed
       topology information stored in the _d_i_g___p_l_u_s file.

SSEEEE AALLSSOO
       _v_._s_u_p_p_o_r_t
       _p_a_r_s_e_r

AAUUTTHHOORR
       _O_r_i_g_i_n_a_l version of _r_._p_o_l_y:
       Jean Ezell and Andrew Heekin,
       U.S. Army Construction Engineering Research Laboratory


       _M_o_d_i_f_i_e_d program for smoothed lines:
       David Satnik, Central Washington University
       Updated 2001 by Andrea Aime, Modena, Italy

       _L_a_s_t _c_h_a_n_g_e_d_: _$_D_a_t_e_: _2_0_0_2_/_0_1_/_2_5 _0_5_:_4_5_:_3_4 _$



GRASS 5.0							     r.poly(1)
