Proximity

grid-functions proximity

syntax

  • proximity(grid_data_item, kernel)

definition

proximity(grid_data_item, kernel) results in a convolution of a grid_data_item and a kernel.

For each cell in the grid_data_item, the values of the cell and it’s neighbourhood cells are multiplied with the corresponding values in the kernel taking that cell as the focal point in the kernel. The resulting cell value is the maximum of these multiplications.

The resulting value-type is float32 or float64, based on the value type of the grid_data_item. The resulting domain-unit is the domain unit of the grid_data_item attribute.

Because the proximity function uses a Fast Fourier Transformation, calculating results is fast even with large kernels.

In other GIS software this operation is also known as the focal statistics, statistic type: MAXIMUM

description

See potential-with-kernel for more information on how to configure different kernels.

applies to

  • attribute grid_data_item with float32 or float64 value-type

conditions

The domain unit of grid_data_item must be a Point value type of the group CanBeDomainUnit.

example

attribute<float32> proxgrid (GridDomain) := proximity(float32(sourcegrid), pot3Range/RelWeight);

sourcegrid

         
null 0 0 0 1
0 0 2 1 1
0 2 3 3 3
1 1 1 3 0
0 1 0 1 3

GridDomain, nr of rows = 5, nr of cols = 5

proxgrid

         
0 0.18 0.23 0.18 0.18
0.18 0.26 0.35 0.35 0.35
0.24 0.35 0.53 0.53 0.53
0.18 0.26 0.35 0.53 0.35
0.12 0.18 0.26 0.35 0.53

GridDomain, nr of rows = 5, nr of cols = 5