Create grid

Create grid

In a previous post I showed how it was possible to create a polygon using variables inside the WKT expressions. Now we'll see how it is possible to create a grid in few lines of GGL2 code.

Consider that we want to create a grid which cell size is 100x100 and that covers the (0, 0)-(1000, 1000) extent. By using two nested loops that run from 0 to 1000 in increments of 100 it is possible to obtain the upper left corner of every cell:

foreach x1 in 0 .. 1000 step 100 {

foreach y1 in 0 .. 1000 step 100 {

show x1 + ', ' + y1;

}

}

Now in the body of the inner loop we can create a cell using pseudo WKT and add it to a resulting collection:

grid = [as geometry];

width = 100;

height = 100;

foreach x1 in 0 .. 1000 step width {

foreach y1 in 0 .. 1000 step height {

double x2 = x1 + width;

double y2 = y1 + height;

geometry polygon = POLYGON((x1 y1, x2 y1, x2 y2, x1 y2, x1 y1));

add polygon to grid;

}

}

Simple, right? The only thing that may worth explaining is the creation of an empty sequence in the first line... but that will be another post. I'll also show how to package this as an algorithm and to use the extent of an existing data source as the area to cover with the grid.