v.build.polylines(1)   Grass User's Manual   v.build.polylines(1)



NNAAMMEE
       _v_._b_u_i_l_d_._p_o_l_y_l_i_n_e_s  - Build polylines from lines.

       _(_G_R_A_S_S Vector Program)

SSYYNNOOPPSSIISS
       vv..bbuuiilldd..ppoollyylliinneess

       vv..bbuuiilldd..ppoollyylliinneess hheellpp

       vv..bbuuiilldd..ppoollyylliinneess     [--aaccooqq   ]   iinnppuutt_n_a_m_e    output_n_a_m_e
       _t_y_p_e_=_n_a_m_e

DDEESSCCRRIIPPTTIIOONN
       _v_._b_u_i_l_d_._p_o_l_y_l_i_n_e_s  builds polylines from the  lines  in	a
       binary  vector  file.   It outputs the polylines in either
       binary or ASCII vector format, and  if  requested,  copies
       the attribute and category files from the original file.


       A  line	is  a single straight line segment defined by one
       start node, one end node and no other nodes.   A  polyline
       is  also  defined  by  one start node, one end node and no
       other nodes, but  is  made  of  two  or	more  consecutive
       straight  line segments.  The connections between the con-
       stituent line segments of a  polyline  do  not  appear  as
       nodes in the vector map.


       Polylines  provide  the most appropriate representation of
       curved lines when it is	important  that  nodes	serve  to
       define  topology  rather  than geometry.  Curved lines are
       usually digitized as polylines, but  these  are	sometimes
       broken  into their constituent straight line segments dur-
       ing   conversion  from  one  data   format   to	 another.
       _v_._b_u_i_l_d_._p_o_l_y_l_i_n_e_s
	can  be used to rebuild such broken polylines.



OOPPTTIIOONNSS
       The  program can be run either non-interactively or inter-
       actively. To run _v_._b_u_i_l_d_._p_o_l_y_l_i_n_e_s
	non-interactively, the user must specify _i_n_p_u_t	and  _o_u_t_-
       _p_u_t   file names on the command line.  The line	_t_y_p_e  and
       flags are optional.


       To run _v_._b_u_i_l_d_._p_o_l_y_l_i_n_e_s  interactively	the  user  should
       simply type vv..bbuuiilldd..ppoollyylliinneess
	on  the  command  line,  in  which  case the program will
       prompt for  parameter  values  using  the  standard  GRASS
       interface described in the manual entry for _p_a_r_s_e_r .




       FFllaaggss::

       --aa  Make the _o_u_t_p_u_t  file an ASCII vector map instead of a
	   binary vector map.

       --cc  Copy   the	attribute   (`dig_att')   and	 category
	   (`dig_cats')  files associated with the _i_n_p_u_t  file to
	   new files with the _o_u_t_p_u_t  file name.  You should  set
	   this  flag  if you wish to retain category information
	   in the new binary file.

       --oo  Silently overwrite the _o_u_t_p_u_t  file if  it  exists  in
	   the	 current  mapset.  When  this  flag  is  not  set
	   _v_._b_u_i_l_d_._p_o_l_y_l_i_n_e_s  will refuse to create  the   _o_u_t_p_u_t
	   file  if  a file of the same name exists in either the
	   `dig' or the `dig_ascii' mapset elements.

       --qq  Run (relatively) quietly.  Specifically, do	not  pro-
	   vide  information   (including  warnings)  about  each
	   polyline.



       PPaarraammeetteerrss::

       iinnppuutt_n_a_m_e
	   The name of a binary vector map layer containing lines
	   (and possibly some polylines).

       oouuttppuutt_n_a_m_e
	   The	name of the ASCII vector map to be created in the
	   dig_ascii mapset  element.

       ttyyppee_n_a_m_e
	   The type of each new polyline  can  be  set	from  the
	   _i_n_p_u_t  map, or  alternatively all new polylines can be
	   bulk labeled as either lines, area edges, or points.

	   Options: source, line, area, point.


NNOOTTEESS
       For full functionality _v_._b_u_i_l_d_._p_o_l_y_l_i_n_e_s  requires  _v_._s_u_p_-
       _p_o_r_t  and _v_._i_n_._a_s_c_i_i .


       If  the	lines  that  make  up a polyline are of different
       types, then _v_._b_u_i_l_d_._p_o_l_y_l_i_n_e_s
	will set  the  type  from  the	first  constituent  line.
       _v_._b_u_i_l_d_._p_o_l_y_l_i_n_e_s  will issue a warning unless the flag _-_q
       has  been set.  It is possible to keep a list of all  such
       warnings by redirecting	standard output to a file.


       If  the	lines  that  make  up  a  polyline have different
       attribute values  then  _v_._b_u_i_l_d_._p_o_l_y_l_i_n_e_s   will  set  the
       attribute  value  of the polyline to that of the last line
       (this is the behaviour of  _v_._s_u_p_p_o_r_t , which  is  used  to
       assign  the  attribute  values).   Any  warnings issued by
       _v_._s_u_p_p_o_r_t  will be visible unless the flag  _-_q	has  been
       set.


       _v_._b_u_i_l_d_._p_o_l_y_l_i_n_e_s   correctly handles _i_n_p_u_t  maps contain-
       ing lines, area edges and points.  Lines  and  area  edges
       will  be  converted  to	polylines   of	the desired type.
       Areas are only guaranteed to be	preserved  if  the   con-
       stituent  lines	of the polylines that define them are all
       area edges in  the input map. Points  will  remain  points
       provided  that _t_y_p_e  has been set to `source'.  It is pos-
       sible to convert lines and area edges to  points  or  vice
       versa, but this is rarely useful.


       Use  _v_._i_m_p_o_r_t  to convert an ASCII _o_u_t_p_u_t  map to a binary
       vector map.



SSEEEE AALLSSOO
       _v_._i_m_p_o_r_t, _v_._s_u_p_p_o_r_t, _v_._i_n_._a_s_c_i_i, _p_a_r_s_e_r



AACCKKNNOOWWLLEEDDGGEEMMEENNTTSS
       This program was written during the author's tenure  of	a
       Leverhulme  Special Research Fellowship at University Col-
       lege London.



AAUUTTHHOORR
       Mark Lake, Institute of	Archaeology,  University  College
       London.



BBUUGGSS
       Please email mark.lake@ucl.ac.uk if you find any bugs.



       _L_a_s_t _c_h_a_n_g_e_d_: _$_D_a_t_e_: _2_0_0_2_/_0_1_/_2_5 _0_5_:_4_5_:_3_5 _$



GRASS 5.0				     v.build.polylines(1)
