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The basic idea of the different Kriging methods is the same. If x denotes a point in space and Z is a function of x which is known in the n observation points x₁, x₂, .., x_n, we look for an estimate Z^*(x₀) of Z(x₀) in an non-measured location of the form:

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1. Select some series from the Select series list box.
2. Select the interpolation function to use and enter the function parameters (i.e. Kriging or inverse distance).
3. Enter the appropriate Grid Characteristics, explained in the Grid Characteristics section.
4. Press the <Execute> button to start the computation.
5. Enter a filename for the ASCII Grid file where the computed data must be stored to.
6. To show the results in Netter, select the "Options" - "Map Options" menu and load the ASCII file as a grid.

ASCII

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Raster File Format

The interpolated data are stored in an ASCII raster file format, also called the Arc/Info ASCII Grid file format. This is a simple and common format that can be used by many GIS, like ArcInfo and ArcView.
The format is very simple, basically a header followed by a list of cell values. The header that includes the following keywords and values: =

ncols

Section
Column width 15% ncols: nrows: xllcenter or xllcorner: yllcenter or yllcorner: cellsize: nodata_value: Column width 85%

number of columns in the data set

.= nrows

number of rows in the data set

.= xllcenter or xllcorner

x-co-ordinate of the centre or lower left corner of the lower left cell

.= yllcenter or yllcorner

y-co-ordinate of the centre or lower left corner of the lower left cell

.= cellsize

cell size of the data set, equal for x and y direction

.nodata_

value

= value

in the file assigning to cells whose value is unknown. The nodata_value default is -9999

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The first row of the data is the top of the data set, moving from left to right. Cell values should be limited by spaces. The number of cell values must be equal to the number of rows times the number of columns.

Example:

Section
Column width 10% NCOLS NROWS XLLCORNER YLLCORNER CELLSIZE NODATA_VALUE Column width 90% 54

NROWS

76

XLLCORNER

214834.1

YLLCORNER

565086

CELLSIZE

500

NODATA_VALUE

-999.99

377 372 366 362 357 353 348 344 340 336 ....
333 330 328 326 326 327 330 334 339 345 ....
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Presentation of Grids in Netter

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To add a static grid file as a map layer in Netter follow these steps:
1. Select "Options" - "Map Options" from the Netter menu.
2. Press the <Add Layer>, top left button and select a ASCII grid file

3. Press the <OK> button

From the Map Options menu the grid map can be customised to the needs of the user. Some of the possible customisation options are:

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