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{alias:son}
h2. Name

*son* — Sonar data gridding

h2. Syntax
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*son ppg* \[*inc*] | \[_nx ny_] | \[*long*] \[*all | four*] \[*tri*] \[*eig*] \[*eigone*] \[*low*] \[*hi*] \[*dob*] \[*auto*] \[*count*] \[*mrf*] 

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h2. Description

Specialized command for gridding sonar data or large point sets. The *son* without the *ppg* option is covered by the command [grp] . 

The *son ppg* is a snapping algorithm of input points to the grid result. The algorithm will snap free point data into a grid of size _nx ny_. The snap gridding will make defined grid nodes of each node that is closest to an input point. If more than one point are sorted to a node, the node value will be the average of the point values. A count grid telling the number of coincident points can be generated. 

h2. Arguments

{indent}No arguments, 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} 
*long* _num_ 
{indent}Create a grid with _num_ nodes for the longest side. Use the same increment for the shortest side.{indent} 
*tri* 
{indent}The three nearest nodes will be used.{indent} 
*all | four* 
{indent}All four nodes surrounding a point will be used.{indent} 
*eig* 
{indent}All eigth nodes surrounding a point including the nearest will be used.{indent} 
*eigone* 
{indent}All eigth nodes surrounding a point will be used and the value 1 will be placed.{indent} 
*low* 
{indent}If coincident points, the lowest will be used and placed in the nearest node.{indent} 
*hi* 
{indent}If coincident points, the highest will be used and placed in the nearest node.{indent} 
*dob* 
{indent}Double check that the first point will be placed in the nearest node and the next coinciding in the three nearest.{indent} 
*auto* 
{indent}The x and y increments are found from the input points. Useful for cases where the input points already are orginized in a grid system.{indent}
*count* 
{indent}The generated grid will have the counting of coincident points.{indent} 
*mrf* 
{indent}Make reference grid  (boundary grid) and reference line around a point set. The reference grid is saved in *active* and the reference line is saved in workspace *refLine*. Look at the options for detailed control.{indent} 
*mrf* _num_ 
{indent}Create a boudaryboundary grid with _num_ nodes for the sides. Points within the boundary grid will define the boundary.{indent} 
_nx ny_ \[*nodraw*] 
{indent}Create a boudaryboundary grid with _nx ny_ nodes for the sides. Points within the boundary grid will define the boundary. The *nodraw* option will prevent the derived boundary line to de drawn.{indent}
*mrf dis* _distance_ 
{indent}Create a boundary grid so that points separated less than _distance_ will be within the same boundary.{indent} 

h2. Examples

h3. Ex.1: Snap gridding of points

{noformat:|borderWidth=1|bgColor=#eeeeee}
# Snap 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 55        ;# Make 55 random points
poi               ;# Display points
son ppg 9 9       ;# Make grid of dimension
poi 2             ;# Display grid points
map               ;# Map the grid
und 0             ;# Make all undefined cells to 0
poll              ;# Draw the grid lines
{noformat}

The above example produces this image. 

The example demonstrates how the snapping is performed 

!att:_img_ref^cmd_sonppg.png!
_Snap gridding showing input points (black) and grid points (red)_

h2. See also

[grp - Grid points and lines], [fmo - Fast modelling]
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