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NAME

v.kriging - Interpolates 2D or 3D raster based on input values located on 2D or 3D point vector layer (method ordinary kriging extended to 3D).

KEYWORDS

raster, 3D raster, ordinary kriging - for 2D and 3D data

SYNOPSIS

v.kriging
v.kriging --help
v.kriging [-2but] input=name [layer=string] phase=string [report=name] [hz_function=string] [output=string] [crossvalid=name] [vert_function=string] [final_function=string] [final_vert_function=string] [atrend=float] [btrend=float] [ctrend=float] [dtrend=float] [fileformat=string] icolumn=name [zcolumn=name] [azimuth=float] [zenith_angle=float] [lmax=float] [vmax=float] [lpieces=integer] [vpieces=integer] [td=float] [hz_nugget=float] [vert_nugget=float] [final_nugget=float] [final_vert_nugget=float] [hz_sill=float] [vert_sill=float] [final_sill=float] [final_vert_sill=float] [hz_range=float] [vert_range=float] [final_range=float] [final_vert_range=float] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-2
Force 2D interpolation even if input is 3D
-b
Compute bivariate variogram (3D interpolation only)
-u
Compute univariate variogram (3D interpolation only)
-t
Eliminate trend if variogram is parabolic
--overwrite
Allow output files to overwrite existing files
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog

Parameters:

input=name [required]
Name of input vector points map
Or data source for direct OGR access
layer=string
Layer number or name
Vector features can have category values in different layers. This number determines which layer to use. When used with direct OGR access this is the layer name.
Default: 1
phase=string [required]
Phase of interpolation. In the initial phase, there is empirical variogram computed. In the middle phase, function of theoretical variogram is chosen by the user and its coefficients are estimated empirically. In the final phase, unknown values are interpolated using theoretical variogram from previous phase.
Options: initial, middle, final
report=name
File to write the report
hz_function=string
Horizontal variogram function
Options: linear, exponential, spherical, gaussian, bivariate
output=string
Name for output 2D/3D raster map
crossvalid=name
File to write the results of cross validation
vert_function=string
Vertical variogram function
Options: linear, exponential, spherical, gaussian, bivariate
final_function=string
Final variogram function (anisotropic or horizontal component of bivariate variogram)
Options: linear, exponential, spherical, gaussian, bivariate
final_vert_function=string
Final variogram function (vertical component of bivariate variogram)
Options: linear, exponential, spherical, gaussian, bivariate
atrend=float
Trend: f(x,y,z) = a*x + b*y + c*z + d
Default: 0.0
btrend=float
Trend: f(x,y,z) = a*x + b*y + c*z + d
Default: 0.0
ctrend=float
Trend: f(x,y,z) = a*x + b*y + c*z + d
Default: 0.0
dtrend=float
Trend: f(x,y,z) = a*x + b*y + c*z + d
Default: 0.0
fileformat=string
File format to save variogram plot (empty: preview in Gnuplot terminal)
Options: cdr, dxf, eps, tex, pdf, png, svg
icolumn=name [required]
Attribute column containing input values for interpolation
zcolumn=name
Attribute column containing z coordinates (only for 3D interpolation based on 2D point layer)
azimuth=float
Azimuth of variogram computing (isotrophic)
Default: 45.0
zenith_angle=float
Zenith angle of variogram computing (isotrophic)
Default: 0.0
lmax=float
Maximum distance in horizontal direction
vmax=float
Maximum distance in horizontal direction (only for 3D variogram)
lpieces=integer
Number of horizontal lags
vpieces=integer
Number of vertical lags (only for 3D variogram)
td=float
Angle of variogram processing
Default: 45.0
hz_nugget=float
Nugget effect of horizontal variogram
Default: 0.0
vert_nugget=float
Nugget effect of vertical variogram
Default: 0.0
final_nugget=float
Nugget effect of anisotropic variogram (or horizontal component of bivariate variogram)
Default: 0.0
final_vert_nugget=float
For bivariate variogram only: nuget effect of vertical component
Default: 0.0
hz_sill=float
Sill of horizontal variogram
vert_sill=float
Sill of vertical variogram
final_sill=float
Sill of anisotropic variogram (or horizontal component of bivariate variogram)
final_vert_sill=float
For bivariate variogram only: sill of vertical component
hz_range=float
Range of horizontal variogram
vert_range=float
Range of vertical variogram
final_range=float
Range of anisotropic variogram (or horizontal component of bivariate variogram)
final_vert_range=float
Range of final variogram: one value for anisotropic, two values for bivariate (hz and vert component)

Table of contents

DESCRIPTION

v.kriging constructs 2D / 3D raster from the values located on discrete points using interpolation method ordinary kriging. In order to let the user decide on the process and necessary parameters, the module performance is divided into three phases:

EXAMPLES

To get optimal results, it is necessary to test various initial settings, anisotropic ratios and variogram functions. Input (2D or 3D point layer) must contain values to be interpolated in the attribute table.

3D kriging

General commands
v.kriging phase=initial in=input_layer icol=name report=report_file.txt file=png
v.kriging in=input_layer phase=middle hz_fun=exponential vert_fun=exponential ic=name file=png  \
hz_range=double vert_range=double [hz_sill=double vert_sill=double hz_nugget=double vert_nugget=double] -u
v.kriging in=input_layer phase=final final_fun=exponential final_range=double \ 
[final_sill=double final_nugget=double] icol=name file=png out=name crossval=crossval_file.txt

Commands based on the dataset of Slovakia 3D precipitation (Mitasova and Hofierka, 2004). For more detailed information check case studies. Another examples of 3D interpolation are available in (Stopkova, 2014).

v.kriging phase=initial in=precip3d@PERMANENT ic=precip report=precip3d.txt file=png --o
v.kriging in=precip3d@PERMANENT phase=middle hz_fun=exponential vert_fun=gaussian ic=precip file=png hz_range=100000. vert_range=1600 --o -u 
v.kriging in=precip3d@PERMANENT phase=middle hz_fun=exponential vert_fun=gaussian ic=precip \
file=png hz_range=100000. vert_range=1600 --o -u 
Note: 3D points in this example are concentrated on the Earth's surface. Thus the deeper / higher, the less accurate result of interpolation.

2D kriging

General commands

v.kriging phase=initial in=input_layer icol=name report=report_file.txt file=png -2
v.kriging in=input_layer phase=final final_function=linear icol=name file=png \
  out=name crossval=crossval_file.txt -2

Commands based on 500 random points extracted from input points of Digital Elevation Model (DEM) elev_lid792_randpts from the North Carolina dataset (Neteler and Mitasova, 2004). See the case studies.

v.kriging phase=initial in=elev_lid792_selected ic=value azimuth=45. td=45. \
report=lid792_500_linear.txt -2 --o
v.kriging in=elev_lid792_selected phase=final final_function=linear ic=value \
file=png out=lid792_500_linear crossval=lid792_500_xval_linear.txt -2 --o

TODO

Recommendations

REFERENCES

Mitasova, H. and Hofierka, J. (2004). Slovakia Precipitation data. Available at https://grass.osgeo.org/download/sample-data/.
Neteler, M. and Mitasova, H. (2004). Open Source GIS: A GRASS GIS Approach. 2nd Ed. 401 pp, Springer, New York. Online Supplement: http://www.grassbook.org
Stopkova, E. (2014). Development and application of 3D analytical functions in spatial analyses (Unpublished doctoral dissertation). The Department of Theoretical Geodesy, Faculty of Civil Engineering of Slovak University of Technology in Bratislava, Slovakia.

SEE ALSO

v.vol.rst
v.krige

REQUIREMENTS

AUTHOR

Eva Stopkova
functions taken from another modules are cited above the function or at the beginning of the file (e.g. quantile.cpp that uses slightly modified functions taken from the module r.quantile (Clemens, G.))

Last changed: $Date: 2017-06-08 12:32:49 +0200 (Thu, 08 Jun 2017) $

SOURCE CODE

Available at: v.kriging source code (history)


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