r.surf.contour(1)      Grass User's Manual	r.surf.contour(1)



NNAAMMEE
       rr..ssuurrff..ccoonnttoouurr	- Surface generation program from raster-
       ized contours.
       _(_G_R_A_S_S _R_a_s_t_e_r _P_r_o_g_r_a_m_)

SSYYNNOOPPSSIISS
       rr..ssuurrff..ccoonnttoouurr
       rr..ssuurrff..ccoonnttoouurr hheellpp
       rr..ssuurrff..ccoonnttoouurr [--ff] iinnppuutt==_n_a_m_e oouuttppuutt==_n_a_m_e

DDEESSCCRRIIPPTTIIOONN
       _r_._s_u_r_f_._c_o_n_t_o_u_r creates a raster elevation map from a  ras-
       terized	contour  map.	Elevation  values  are determined
       using procedures similar to a manual methods.   To  deter-
       mine  the  elevation of a point on a contour map, an indi-
       vidual might interpolate its value from those of  the  two
       nearest contour lines (uphill and downhill).


       _r_._s_u_r_f_._c_o_n_t_o_u_r  works in a similar way.	Initially, a vec-
       tor map of the contour lines is made with the elevation of
       each  line  as its label (see _v_._d_i_g_i_t ).  When the program
       _v_._t_o_._r_a_s_t

       is run on the vector map, continuous  "lines"  of  rasters
       containing  the	contour line values will be the input for
       _r_._s_u_r_f_._c_o_n_t_o_u_r. For each cell in the input map, either the
       cell  is  a contour line cell (which is given that value),
       or a flood fill is generated from that spot until the fill
       comes to two unique values. So the _r_._s_u_r_f_._c_o_n_t_o_u_r linearly
       interpolates between contour lines. The flood fill is  not
       allowed	to  cross over the rasterized contour lines, thus
       ensuring that an uphill and downhill contour value will be
       the  two  values chosen.  _r_._s_u_r_f_._c_o_n_t_o_u_r interpolates from
       the uphill and downhill values by the true distance.


       The program will be  run  non-interactively  if	the  user
       specifies  the  program	parameter values and desired flag
       settings on the command line, using the form:


       rr..ssuurrff..ccoonnttoouurr [--ff] iinnppuutt==_n_a_m_e oouuttppuutt==_n_a_m_e



       Alternately, the user can simply  type  rr..ssuurrff..ccoonnttoouurr  on
       the  command  line,  without  program  arguments.  In this
       case, the user will be  prompted  for  needed  inputs  and
       option  choices	using  the  standard GRASS user interface
       described in the manual entry for _p_a_r_s_e_r





   FFllaaggss::
       --ff     Invoke fast, but	memory-intensive  program  opera-
	      tion.






   PPaarraammeetteerrss::
       iinnppuutt==_n_a_m_e
	      Name  of an existing raster map layer that contains
	      a set of initial category values (i.e., some  cells
	      contain  known  category values (denoting contours)
	      while the rest contain zeros (0)).

       oouuttppuutt==_n_a_m_e
	      Name to be assigned to new output raster map  layer
	      that  represents a smooth (e.g., elevation) surface
	      generated from the known	category  values  in  the
	      input raster map layer.


NNOOTTEESS
       _r_._s_u_r_f_._c_o_n_t_o_u_r  works  well  under  the	following circum-
       stances: 1) the contour lines extend to the  the  edge  of
       the current region, 2) the program is run at the same res-
       olution as that of the input map, 3)  there  are  no  dis-
       jointed	contour  lines,  and  4)  no  spot elevation data
       BETWEEN contour lines exist.  Spot elevations at the  tops
       of  hills  and  the  bottoms  of depressions, on the other
       hand, improve the output greatly.   Violating  these  con-
       straints  will  cause non-intuitive anomalies to appear in
       the output map.	Run _r_._s_l_o_p_e_._a_s_p_e_c_t
	on _r_._s_u_r_f_._c_o_n_t_o_u_r results to locate potential  anomalies.


       The  running  of  _r_._s_u_r_f_._c_o_n_t_o_u_r  is very sensitive to the
       resolution of rasterized vector map.  If multiple  contour
       lines  go  through  the	same raster, slight anomalies may
       occur.  The speed of _r_._s_u_r_f_._c_o_n_t_o_u_r is  dependent  on  how
       far "apart" the contour lines are from each other (as mea-
       sured in rasters).  Since a flood fill algorithm is  used,
       the  program's  running	time will grow exponentially with
       the distance between contour lines.


       _r_._s_u_r_f_._c_o_n_t_o_u_r

SSEEEE AALLSSOO
       _r_._s_u_r_f_._i_d_w

       _r_._s_u_r_f_._i_d_w_2

       _s_._s_u_r_f_._i_d_w

       _v_._d_i_g_i_t

       _v_._t_o_._r_a_s_t

       _r_._s_l_o_p_e_._a_s_p_e_c_t

       _p_a_r_s_e_r

AAUUTTHHOORR
       Chuck Ehlschlaeger,  U.S.  Army	Construction  Engineering
       Research Laboratory



       _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.surf.contour(1)
