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{alias:tps}
h2. Name

*tps* — Thin plate spline gridding of well data

h2. Syntax
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*tps* \[*inc*] | \[_nx ny_] \[*nosmo*] \[*ref* _referencegrid_] 

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h2. Description

Gridding command for a small number of points (< 100) that applies _thin plate spline_ theory; i.e. a thin plate is passing through the input points the same way as a spline curve is interpolating. That means the generated surface will have minimum tension as the tension energy is released as much as possible.

The gridding may bw usefull for gridding well data that represents subsurface structures that have released their energy.

The algorithm shows good extrapolation qualities. After gridding the result grid is saved in workspace as _tpsgrid_.

The *tps* command is available in the _oil and gas_ plugin.

The theory is described here: [Thin plate spline|http://en.wikipedia.org/wiki/Thin_plate_spline]. 

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TPS has been widely used as the non-rigid transformation model in image alignment and shape matching.

The popularity of TPS comes from a number of advantages: (1) the interpolation is smooth with derivatives of any order; (2) the model has no free parameters that need manual tuning; (3) it has closed-form solutions for both warping and parameter estimation; and (4) there is a physical explanation for its energy function.

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h2. Arguments

No arguments. 
{indent}The grid will have the same number of rows and columns as the last grid that set the @nrow @ncol variables.{indent} 
*inc* _xinc yinc_ 
{indent}Create grid model grid with increments _xinc_ and _yinc_ .{indent} 
_nx ny_ 
{indent}Create a grid with nx times ny grid cells.{indent} 
*nosmo* 
{indent}A default smoothing is applied. This can be prevented with the *nosmo* option.{indent} 
*ref* _referencegrid_ 
{indent}Apply a reference grid in workspace _referencegrid_ for grid layout. Dimension of the grid is taken from the _referencegrid_.{indent} 

h2. Examples

h3. Ex.1: Thin plate spline interpolating of points

{noformat:|borderWidth=1|bgColor=#eeeeee}
# Surface model gridding
z                 ;# Erase screen
win demo          ;# Get demo window (450000 460000 6450000 6460000 1000 4000)
spe bgc whi       ;# Specify background color to white
mak ran 11        ;# Make 11 random points
poi 2             ;# Display point with size width 2
tps 222 222       ;# Make grid of dimension 222 x 222
map               ;# Map the grid
{noformat}

The above example produces this image. 

!att:_img_ref^cmd_tps.png!
_Thin plate spline gridding example_

h2. See also

[gen - Generate grid], [grp - Grid points and lines], [fmo - Fast modelling], [gsu - grid],  [trg - Triangulate point data]

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