Performing Ordinary Kriging in SAGA via QGIS SEXTANTE Plug-in?

Question

I'm trying to learn how to apply the kriging analysis in QGIS using the SEXTANTE plug-in and SAGA tools. It appears that I have my SEXTANTE and SAGA folders configured properly according to the user guide. I've never used a kriging function before and I can't find a good resource from SAGA explaining the different input parameters. Does anyone have experience using the ordinary kriging tool in SAGA that can provide advice or a reference? I'm currently getting the following error message in QGIS:

An error has occured while executing Python code: 
Traceback (most recent call last):   
File "C:/Documents and Settings/PS/.qgis/python/plugins\sextante\gui\ParametersDialog.py", line 137, in accept if self.setParamValues():   
File "C:/Documents and Settings/PS/.qgis/python/plugins\sextante\gui\ParametersDialog.py", line 91, in setParamValue if not self.setParamValue(param, self.paramTable.valueItems[param.name]):   
File "C:/Documents and Settings/PS/.qgis/python/plugins\sextante\gui\ParametersDialog.py", line 129, in setParamValue return param.setValue(widget.getValue())   
File "C:/Documents and Settings/PS/.qgis/python/plugins\sextante\parameters\ParameterExtent.py", line 11, in setValue if value is None: NameError: global name 'value' is not defined

Answer 1

If you never have run kriging before, you should understand what you are doing. If this is not the case, get a textbook on geostatistics. Anyway, most parameters are there to determine the variogram:

johan@cdh7:~$ saga_cmd libgeostatistics_kriging 5
_____________________________________________
  #####   ##   #####    ##
 ###     ###  ##       ###
  ###   # ## ##  #### # ##
   ### ##### ##    # #####
##### #   ##  ##### #   ##
_____________________________________________

library path:   /usr/lib/saga
library name:   libgeostatistics_kriging
module name :   Ordinary Kriging
author      :   (c) 2008 by O.Conrad
_____________________________________________
go...
Usage: 5 [-GRID <str>] [-VARIANCE <str>] -SHAPES <str> [-FIELD <str>] [-BVARIANCE] [-TARGET <str>] [-MODEL <str>] [-BLOCK] [-DBLOCK <str>] [-BLOG] [-NUGGET <str>] [-SILL <str>] [-RANGE <str>] [-LIN_B <str>] [-EXP_B <str>] [-POW_A <str>] [-POW_B <str>] [-MAXRADIUS <str>] [-NPOINTS_MIN <str>] [-NPOINTS_MAX <str>] [-USER_CELL_SIZE <str>] [-USER_FIT_EXTENT] [-USER_X_EXTENT_MIN <str>] [-USER_X_EXTENT_MAX <str>] [-USER_Y_EXTENT_MIN <str>] [-USER_Y_EXTENT_MAX <str>] [-SYSTEM_SYSTEM_NX <num>] [-SYSTEM_SYSTEM_NY <num>] [-SYSTEM_SYSTEM_X <str>] [-SYSTEM_SYSTEM_Y <str>] [-SYSTEM_SYSTEM_D <str>] [-GRID_GRID <str>] [-GRID_VARIANCE <str>]
  -GRID:<str>               Grid
    Data Object (optional output)
  -VARIANCE:<str>           Variance
    Data Object (optional output)
  -SHAPES:<str>             Points
    Shapes (input)
  -FIELD:<str>              Attribute
    Table field
  -BVARIANCE                Create Variance Grid
    Boolean
  -TARGET:<str>             Target Grid
    Choice
    Available Choices:
    [0] user defined
    [1] grid system
    [2] grid
  -MODEL:<str>              Variogram Model
    Choice
    Available Choices:
    [0] Spherical Model
    [1] Exponential Model
    [2] Gaussian Model
    [3] Linear Regression
    [4] Exponential Regression
    [5] Power Function Regression
  -BLOCK                    Block Kriging
    Boolean
  -DBLOCK:<str>             Block Size
    Floating point
    Minimum: 0.000000
  -BLOG                     Logarithmic Transformation
    Boolean
  -NUGGET:<str>             Nugget
    Floating point
    Minimum: 0.000000
  -SILL:<str>               Sill
    Floating point
    Minimum: 0.000000
  -RANGE:<str>              Range
    Floating point
    Minimum: 0.000000
  -LIN_B:<str>              Linear Regression
    Floating point
  -EXP_B:<str>              Exponential Regression
    Floating point
  -POW_A:<str>              Power Function - A
    Floating point
  -POW_B:<str>              Power Function - B
    Floating point
  -MAXRADIUS:<str>          Maximum Search Radius (map units)
    Floating point
    Minimum: 0.000000
  -NPOINTS_MIN:<str>        Min./Max. Number of m_Points
    Value range
  -NPOINTS_MAX:<str>        Min./Max. Number of m_Points
    Value range
  -USER_CELL_SIZE:<str>     Grid Size
    Floating point
    Minimum: 0.000000
  -USER_FIT_EXTENT          Fit Extent
    Boolean
  -USER_X_EXTENT_MIN:<str>  X-Extent
    Value range
  -USER_X_EXTENT_MAX:<str>  X-Extent
    Value range
  -USER_Y_EXTENT_MIN:<str>  Y-Extent
    Value range
  -USER_Y_EXTENT_MAX:<str>  Y-Extent
    Value range
  -SYSTEM_SYSTEM_NX:<num>   Grid System
    Grid system
  -SYSTEM_SYSTEM_NY:<num>   Grid System
    Grid system
  -SYSTEM_SYSTEM_X:<str>    Grid System
    Grid system
  -SYSTEM_SYSTEM_Y:<str>    Grid System
    Grid system
  -SYSTEM_SYSTEM_D:<str>    Grid System
    Grid system
  -GRID_GRID:<str>          Grid
    Grid (input)
  -GRID_VARIANCE:<str>      Variance
    Grid (optional input)