s.sample(1)	       Grass User's Manual	      s.sample(1)



NNAAMMEE
       ss..ssaammppllee - Sample a raster file at site locations.
       _(_G_R_A_S_S _S_i_t_e_s _P_r_o_g_r_a_m_)

SSYYNNOOPPSSIISS
       ss..ssaammppllee
       ss..ssaammppllee hheellpp
       ss..ssaammppllee   [--BBCCllqq]  iinnppuutt==_n_a_m_e  [aattttrr==_t_y_p_e]  [ffiieelldd==_v_a_l_u_e]
       [oouuttppuutt==_n_a_m_e] rraasstt==_n_a_m_e [zz==_n_a_m_e]

DDEESSCCRRIIPPTTIIOONN
       _s_._s_a_m_p_l_e samples a GRASS raster map at the site	locations
       in  the	input file by either cubic convolution interpola-
       tion, bilinear interpolation, or nearest neighbor sampling
       (default).  Category label values may sampled.


       This  program  may  be especially useful when sampling for
       cross validation  of  interpolations  whose  output  is	a
       raster map.

OOPPTTIIOONNSS
   FFllaaggss::
       --BB     Use bilinear interpolation.

       --CC     Use cubic convolution interpolation.

       --ll     Use  raster  category  label values instead of cell
	      values. Labels must be numeric.

       --qq     Quiet. Cut out the chatter.


   PPaarraammeetteerrss::
       iinnppuutt==_n_a_m_e
	      Name of sites list defining sample points.

       aattttrr==_t_y_p_e
	      Site attribute type to use for comparison.

	      OOppttiioonnss:: _n_o_n_e_, _d_i_m_, _c_a_t_, _d_e_c_i_m_a_l

	      If _n_o_n_e is chosen no comparison will be done.

       ffiieelldd==_v_a_l_u_e
	      Site attribute field to use for comparison.

	      Ignored when the attribute is _n_o_n_e or _c_a_t.

       oouuttppuutt==_n_a_m_e
	      Optional name of sites list in which output will be
	      stored.	Standard  output is used if this is miss-
	      ing.

       rraasstt==_n_a_m_e
	      Name of raster map to be sampled.

       zz==_v_a_l_u_e
	      Option scaling factor for values read  from  raster
	      map.   Sampled  values  will  be multiplied by this
	      factor. If omitted, this is set to 1.0.


NNOOTTEESS
       The output site list will have the easting and northing of
       the  input  site  list.	The category value will either be
       the same as the value in the input site list or	a  unique
       value  if there were no categories in the input site list.
       One decimal attribute will be  output  containing  either,
       the  cell  value  of  the raster if no comparison was done
       (i.e. aattttrr==nnoonnee) or it will be the difference between  the
       cell value and the site list attribute value.


       If  --ll is specified, it is important that the raster cate-
       gory label is numeric. No error checking  is  done  except
       for  "no  data"	values as raster category labels. In this
       instance, a warning is issued and a zero value is assumed.


       When NULL values are encountered for a cell, zero value is
       used instead.  In these cases, more acurrate  results  may
       be  obtained by using the default nearest neighbor compar-
       isons.


       This program may not work properly with lat-long data when
       the --BBCC flags are used.


       When interpolation is done (i.e., the --BBCC flags are used),
       values are assumed to be located at the centroid  of  grid
       cells.	Therefore, current resolution settings are impor-
       tant.

SSEEEE AALLSSOO
       _s_._r_a_n_d_o_m

       _s_._k_c_v

       _g_._r_e_g_i_o_n

       _I_m_a_g_e  _S_a_m_p_l_i_n_g	_M_e_t_h_o_d_s  -  GRASS  Tutorial  on  _s_._s_a_m_p_l_e
       (available as s.sample-tutorial.ps.gz)

BBUUGGSS
       Please  send  all  bug fixes and comments to the author or
       the grass development team.

       http://www.geog.uni-hannover/grass/

AAUUTTHHOORR
       James Darrell McCauley ,

       when he was at: Agricultural Engineering Purdue University


       Updated for GRASS 5.0 by Eric G. Miller

       _L_a_s_t _c_h_a_n_g_e_d_: _$_D_a_t_e_: _2_0_0_2_/_0_1_/_2_5 _0_5_:_4_5_:_3_5 _$



GRASS 5.0					      s.sample(1)
