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 interpolation


NNOOTTEESS
       During the interpolation following warning may occur:


       Warning: strip exists with insufficient data

       Warning:  taking  too  long  to	find  points for interpolation--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
       interpolated 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 values 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  Informa-
       tion  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 temporally 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  Regularized	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 Regularized	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_: _$_D_a_t_e_: _2_0_0_3_/_0_2_/_0_5 _1_2_:_4_6_:_0_3 _$



GRASS 5.0							r.fillnulls(1)
