r.surf.idw2(1)	       Grass User's Manual	   r.surf.idw2(1)



NNAAMMEE
       rr..ssuurrff..iiddww22  - Surface generation program.
       _(_G_R_A_S_S _R_a_s_t_e_r _P_r_o_g_r_a_m_)

SSYYNNOOPPSSIISS
       rr..ssuurrff..iiddww22 iinnppuutt==_n_a_m_e oouuttppuutt==_n_a_m_e [nnppooiinnttss==_c_o_u_n_t]

DDEESSCCRRIIPPTTIIOONN
       _r_._s_u_r_f_._i_d_w_2 fills a raster matrix with interpolated values
       generated from a set of	irregularly  spaced  data  points
       using  numerical  approximation (weighted averaging) tech-
       niques.	The interpolated value of a cell is determined by
       values  of nearby data points and the distance of the cell
       from those input points.  In comparison with  other  meth-
       ods, numerical approximation allows representation of more
       complex surfaces (particularly those with  anomalous  fea-
       tures), restricts the spatial influence of any errors, and
       generates the interpolated surface from the  data  points.
       It is the most appropriate method to apply to most spatial
       data.


       The program will be  run  non-interactively  if	the  user
       specifies  the values of needed program parameters and any
       desired optional parameter values  on  the  command  line,
       using   the   form:   rr..ssuurrff..iiddww22  iinnppuutt==_n_a_m_e  oouuttppuutt==_n_a_m_e
       [nnppooiinnttss==_c_o_u_n_t]



       Alternately, the user can simply type rr..ssuurrff..iiddww22  on  the
       command	line,  without	program arguments.  In this case,
       the user will be prompted for parameter values  using  the
       standard  GRASS	user  interface  described  in the manual
       entry for _p_a_r_s_e_r.

   PPaarraammeetteerrss::
       iinnppuutt==_n_a_m_e
	      Name of an input raster map layer that  contains	a
	      set  of  irregularly spaced data values; i.e., some
	      cells contain known data values while the rest con-
	      tain zero (0).

       oouuttppuutt==_n_a_m_e
	      Name  to	be  assigned to the new output raster map
	      layer containing a smooth  surface  generated  from
	      the known data values in the input map layer.

       nnppooiinnttss==_c_o_u_n_t
	      The number of points to use for interpolation.  The
	      default is to use the 12 nearest points when inter-
	      polating the value for a particular cell.
	      Default:	12


NNOOTTEESS
       The  amount  of	memory used by this program is related to
       the number of non-zero data values in the input map layer.
       If  the	input  raster map layer is very dense (i.e., con-
       tains many non-zero data points), the program may  not  be
       able  to get all the memory it needs from the system.  The
       time required to execute  increases  with  the  number  of
       input data points.


       If  the	user  has  a mask set, then interpolation is only
       done for those cells that fall within the mask.	 However,
       all  non-zero data points in the input layer are used even
       if they fall outside the mask.


       This program does not work  with  latitude/longitude  data
       bases.	 Another   surface   generation   program,  named
       _r_._s_u_r_f_._i_d_w, should be used  with  latitude/longitude  data
       bases.


       The user should refer to the manual entries for

       _r_._s_u_r_f_._i_d_w

       _r_._s_u_r_f_._c_o_n_t_o_u_r

       _s_._s_u_r_f_._i_d_w

       _s_._s_u_r_f_._r_s_t
       to  compare  this  surface  generation program with others
       available in GRASS.

SSEEEE AALLSSOO
       _r_._m_a_s_k

       _r_._s_u_r_f_._c_o_n_t_o_u_r

       _r_._s_u_r_f_._i_d_w

       _s_._s_u_r_f_._i_d_w

       _s_._s_u_r_f_._r_s_t

       _r_._s_u_r_f_._g_a_u_s_s

       _r_._s_u_r_f_._f_r_a_c_t_a_l

       _r_._s_u_r_f_._r_a_n_d_o_m

       _r_._s_u_r_f_._i_d_w_2

       _p_a_r_s_e_r

AAUUTTHHOORR
       Michael	 Shapiro,   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.idw2(1)
