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 features from it, converts data to GRASS vector
       format, and smoothes vectors.


       _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 values for  the  raster  map  layer
       will  be  used  to  create  attribute  information 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  bet-
       ter-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 connecting 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
       interactively.	The program will be run non-interactively
       if the user specifies 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  com-
       mand  line  without  program  arguments. In this case, the
       user will be prompted for parameter values and  flag  set-
       tings 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)
