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



NNAAMMEE
       rr..ffiillllnnuullllss  - Fills NULL (no data areas) in input map and
       stores filled map to a new output map. The fill	data  are
       interpolated  from  the	no  data  area	boundaries  using
       s.surf.rst spline interpolation.

       _(_G_R_A_S_S _S_h_e_l_l _S_c_r_i_p_t_)

SSYYNNOOPPSSIISS
       rr..ffiillllnnuullllss


	rr..ffiillllnnuullllss iinnppuutt==_n_a_m_e oouuttppuutt==_n_a_m_e

OOPPTTIIOONNSS
   PPaarraammeetteerrss::
       iinnppuutt==_n_a_m_e
	      raster map containing NULL data area(s)/pixel(s)

       oouuttppuutt==_n_a_m_e
	      raster map with NULL areas filled by RST interpola-
	      tion


NNOOTTEESS
       During the interpolation following warning may occur:


       Warning: strip exists with insufficient data

       Warning:  taking  too  long  to find points for interpola-
       tion--please change the region to area where  your  points
       are


       This warning is generated if large data holes exist within
       the surface.  As the idea of _r_._f_i_l_l_n_u_l_l_s is to  fill  such
       holes,  the user may ignore the warning. The interpolation
       will be continued. However, the user may pay attention  to
       below notes.

AATTTTEENNTTIIOONN
       The  algorithm  is based on _s_._s_u_r_f_._r_s_t regularized splines
       with tension interpolation module which	interpolates  the
       raster  cell  values for NULL data areas from the boundary
       values of the NULL data area. An eventual raster  MASK  is
       respected during the NULL data area(s) filling. The inter-
       polated values are patched into the NULL data  area(s)  of
       the input map and saved into a new raster map.

WWAARRNNIINNGG
       Depending  on  the shape of the NULL data area(s) problems
       may occur due to an insufficient number of input cell val-
       ues  for  the  interpolation  process.  Most problems will
       occur if a NULL data area reaches a large  amount  of  the
       map  boundary.  The  user will have to carefully check the
       result using _r_._m_a_p_c_a_l_c (generating a difference map to the
       input  map)  and/or  _d_._w_h_a_t_._r_a_s_t  to query individual cell
       values.



SSEEEE AALLSSOO
       _r_._f_i_l_l_._d_i_r_, _s_._s_u_r_f_._r_s_t

	Mitas, L., Mitasova, H., 1999, Spatial Interpolation. In:
       P.Longley, M.F. Goodchild, D.J. Maguire, D.W.Rhind (Eds.),
       Geographical Information Systems: Principles,  Techniques,
       Management and Applications, Wiley, pp.481-492

       Mitasova  H.,  Mitas  L.,   Brown  W.M.,   D.P. Gerdes, I.
       Kosinovsky, Baker, T.1995, Modeling spatially  and  tempo-
       rally  distributed  phenomena:  New  methods and tools for
       GRASS GIS. _I_n_t_e_r_n_a_t_i_o_n_a_l _J_o_u_r_n_a_l _o_f _G_I_S,  9  (4),  special
       issue  on  Integrating  GIS  and  Environmental	modeling,
       433-446.

       Mitasova H.  and Mitas L. 1993: Interpolation by  Regular-
       ized  Spline  with Tension: I.  Theory and Implementation,
       _M_a_t_h_e_m_a_t_i_c_a_l _G_e_o_l_o_g_y 25, 641-655.

       Mitasova H.  and Hofierka L. 1993: Interpolation by  Regu-
       larized	Spline	with  Tension: II. Application to Terrain
       Modeling and Surface Geometry Analysis, _M_a_t_h_e_m_a_t_i_c_a_l _G_e_o_l_-
       _o_g_y 25, 657-667.

AAUUTTHHOORRSS
       r.fillnulls: Markus Neteler, University of Hannover


       and authors of s.surf.rst

       _L_a_s_t _c_h_a_n_g_e_d_: _$_D_a_t_e_: _2_0_0_2_/_0_3_/_0_1 _0_0_:_0_8_:_3_1 _$



GRASS 5.0					   r.fillnulls(1)
