r.resamp.rst(1) 	      Grass User's Manual	       r.resamp.rst(1)



NNAAMMEE
       _r_._r_e_s_a_m_p_._r_s_t  -	reinterpolates	and computes topographic analysis from
       input raster file to a new raster file (possibly with different resolu-
       tion) using regularized spline with tension and smoothing.

       (_G_R_A_S_S _R_a_s_t_e_r _P_r_o_g_r_a_m)



SSYYNNOOPPSSIISS
       rr..rreessaammpp..rrsstt

       rr..rreessaammpp..rrsstt hheellpp

       rr..rreessaammpp..rrsstt [[--rr]] [[--dd]] [[--tt]] iinnppuutt = name eeww__rreess = val nnss__rreess = val eelleevv
       = name [ssllooppee = name] [aassppeecctt = name] [ppccuurrvv =  name]  [ttccuurrvv  =  name]
       [mmccuurrvv  = name] [ssmmooootthh = name] [mmaasskkmmaapp = name] [oovveerrllaapp = val] [zzmmuulltt
       = val] [tteennssiioonn = val]



DDEESSCCRRIIPPTTIIOONN
       _r_._r_e_s_a_m_p_._r_s_t

       This program reinterpolates the values a from given raster  file  named
       _i_n_p_u_t  to  a  new  raster file named _e_l_e_v. If _-_r flag is specified, all
       zero elevations in _i_n_p_u_t file are treated as elevations, otherwise they
       are  ignored.  Reinterpolation  (resampling) is done to higher, same or
       lower resolution which is specified by parameters  _e_w___r_e_s  and  _n_s___r_e_s.
       All  resulting  raster  files  are  created for the given region (which
       might be different from the header of the input raster  file).	As  an
       option,	 simultaneously  with  interpolation,  topographic  parameters
       slope, aspect, profile curvature (measured in the direction of steepest
       slope), tangential curvature (measured in the direction of a tangent to
       contour line) or mean curvature are computed and saved as raster  files
       as  specified by the options _s_l_o_p_e_, _a_s_p_e_c_t_, _p_c_u_r_v_, _t_c_u_r_v_, _m_c_u_r_v respec-
       tively.	If _-_d flag is set  the	program  outputs  partial  derivatives
       fx,fy,fxx, fxy,fyy instead of slope, aspect and curvatures.

       For  noisy  data, it is possible to define spatially variable smoothing
       by prividing a raster  file  _s_m_o_o_t_h  containing	smoothing  parameters.
       With  the  smoothing parameter set to zero (_s_m_o_o_t_h is not given or con-
       tains zero data), the resulting surface passes exactly through the data
       points. User can define a raster file named _m_a_s_k_m_a_p, which will be used
       as a mask. The interpolation is skipped for cells which have zero value
       in  mask.  Zero	values	will  be assigned to these cells in all output
       raster files. Parameter _z_m_u_l_t allows the user to rescale  the  z-values
       (useful,  e.g.,	for  transformation  of  elevations  given  in feet to
       meters, so that the proper values of slopes and curvatures can be  com-
       puted).

       Regularized spline with tension is used for the interpolation. The _t_e_n_-
       _s_i_o_n parameter tunes the character of the resulting surface  from  thin
       plate  to membrane. Higher values of tension parameter reduce the over-
       shoots that can appear in surfaces with rapid change of	gradient.  The
       flag  _-_t  can be set to use "dnorm independent tension". The interpola-
       tion is performed for overlaping rectangular  segments.	The  user  can
       define the width of overlap (in number of cells) by option _o_v_e_r_l_a_p.



OOPPTTIIOONNSS
       The  user  can  run  this  program either interactively or non-interac-
       tively.	The program will be run non-interactively if the  user	speci-
       fies  program arguments and flag settings on the command line using the
       form:

       rr..rreessaammpp..rrsstt [[--rr]] [[--dd]] [[--tt]] iinnppuutt = name eeww__rreess = val nnss__rreess = val eelleevv
       =  name	[ssllooppee	=  name] [aassppeecctt = name] [ppccuurrvv = name] [ttccuurrvv = name]
       [mmccuurrvv = name] [ssmmooootthh = name] [mmaasskkmmaapp = name] [oovveerrllaapp = val] [ zzmmuulltt
       = val ] [tteennssiioonn = val]

       Alternatively,  the  user  can simply type  rr..rreessaammpp..rrsstt on the command
       line without program arguments. In this case, the user will be prompted
       for  parameter values and flag settings using the standard GRASS parser
       interface described in the manual entry for _p_a_r_s_e_r .

       FFllaaggss

	--rr Indicates that zeroes in input map represent elevation.

       --dd Output partial derivatives instead of aspect, slope and curvatures

       PPaarraammeetteerrss:

	iinnppuutt =_n_a_m_e

       Use the existing site file _n_a_m_e as input.

	eeww__rreess = _v_a_l

       Set desired east-west resolution to _v_a_l .

	nnss__rreess = _v_a_l

       Set desired north-south resolution to _v_a_l .

       eelleevv = _n_a_m_e

       Output elevation values to raster file named _n_a_m_e .

       ssllooppee = _n_a_m_e

       Output slope or fx values to raster file named _n_a_m_e .

       aassppeecctt = _n_a_m_e

       Output aspect or fy values to raster file named _n_a_m_e .

       ppccuurrvv = _n_a_m_e

       Output profile curvature or fxx values to raster file named _n_a_m_e

       ttccuurrvv=_n_a_m_e

       Output tangential curvature values or fyy to raster file named _n_a_m_e

       mmccuurrvv=_n_a_m_e

       Output mean curvature values or fxy to raster file named _n_a_m_e


       ssmmooootthh=_n_a_m_e

       18 Set smoothing parameter from file _n_a_m_e .

       mmaasskkmmaapp=_n_a_m_e

       Use the existing raster file _n_a_m_e as a mask.

       oovveerrllaapp =_v_a_l

       Use overlap _v_a_l cells to get additional points for interpolation for  a
       given segment. Default value is 3.

	zzmmuulltt =_v_a_l

       Convert z-values using conversion factor _v_a_l . Default value is 1.

	tteennssiioonn = _v_a_l

       Set tension to _v_a_l .



NNOOTTEESS
       _r_._r_e_s_a_m_p_._r_s_t uses regularized spline with tension for interpolation (as
       described in Mitasova and Mitas, 1993). Region is  temporarily  changed
       while writing output files with desired resolution. Topographic parame-
       ters are computed the same way as in s.surf.rst. (See also Mitasova and
       Hofierka,  1993)  Raster  file _s_m_o_o_t_h should contain variable smoothing
       parameters that can be derived from errors, slope, etc.	using	_r_._m_a_p_-
       _c_a_l_c.  The program gives warning when significant overshoots appear and
       higher tension should be used.  However,  with  tension	too  high  the
       resulting  surface  changes  its  behavior  to  membrane  (rubber sheet
       stretched over the data points resulting in a peak or pit in each given
       point and everywhere else the surface goes rapidly to trend). Smoothing
       can also be used to reduce the overshoots. When overshoots  occure  the
       resulting  _e_l_e_v	file  will  have white color in the locations of over-
       shoots since the color table for the output file is the	same  as  col-
       ortable	for raster input file.The program checks the numerical stabil-
       ity of the algorithm by computation of  values  in  given  points,  and
       prints the maximum difference found into the history file of raster map
       _e_l_e_v . Increase in tension is suggested if the difference is  unaccept-
       able. For computation with smoothing set to 0 this difference should be
       0. With smoothing parameter greater than zero the surface will not pass
       through	the  data  points  and the higher the parameter the closer the
       surface will be to the trend.

       The program writes the values of parameters used  in  computation  into
       the comment part of the history file _e_l_e_v as well as the following val-
       ues which help to evaluate the results and choose the suitable  parame-
       ters:  minimum  and  maximum  z	values	in  the  data file (zmin_data,
       zmax_data) and in the interpolated  raster  map	(zmin_int,  zmax_int),
       maximum	difference  between  the  given  and interpolated z value in a
       given point (errtotal),	rescaling  parameter  used  for  normalization
       (dnorm),  which	influences the tension. The program gives warning when
       the user wants to interpolate outside the region given by the header of
       the  input  raster  file, zooming into the area where the points are is
       suggested in this case. When a mask is  used,  the  program  takes  all
       points  in  the	given region for interpolation, including those in the
       area which is masked out, to ensure proper interpolation along the bor-
       der  of	the  mask.  It therefore does not mask out the data points; if
       this is desirable, it must be done outside _r_._r_e_s_a_m_p_._r_s_t .



SSEEEE AALLSSOO
       r.resample, s.surf.rst



AAUUTTHHOORRSS
       _O_r_i_g_i_n_a_l _v_e_r_s_i_o_n _o_f _p_r_o_g_r_a_m _(_i_n _F_O_R_T_R_A_N_)_:

       Lubos Mitas, NCSA, University of Illinois at Urbana Champaign, Il

       Helena Mitasova, US Army CERL, Champaign, Illinois

       _M_o_d_i_f_i_e_d _p_r_o_g_r_a_m _(_t_r_a_n_s_l_a_t_e_d _t_o _C_, _a_d_a_p_t_e_d  _f_o_r	_G_R_A_S_S  _,  _s_e_g_m_e_n_t_a_t_i_o_n
       _p_r_o_c_e_d_u_r_e_)_:

       Irina Kosinovsky, US Army CERL .

       Dave Gerdes, US Army CERL .



RREEFFEERREENNCCEESS
       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, 481-492.

       Mitasova, H. and Mitas, L., 1993. Interpolation by  regularized	spline
       with  tension: I. Theory and implementation, Mathematical Geology No.25
       p.641-656.

       Mitasova, H. and  Hofierka,  L.,  1993.	Interpolation  by  regularized
       spline  with  tension:  II. Application to terrain modeling and surface
       geometry analysis, Mathematical Geology No.25 p.657-667.

	Talmi, A. and Gilat, G., 1977.	Method	for  smooth  approximation  of
       data, Journal of Computational Physics , 23, pp 93-123.

       Wahba,  G.,  1990.  Spline  models  for	observational  data,  CNMS-NSF
       Regional Conference series in applied mathematics, 59, SIAM,  Philadel-
       phia, Pennsylvania.

       _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.resamp.rst(1)
