Class: SpatialAnalysis

The SpatialAnalysis class encapsulates special spatial analysis operations in iLand. For example, the class contains methods to conduct patch size analysis, or calculate the Rumple index.

You can create an instance of this class using the newoperator: new SpatialAnalysis().

Example

// create an object (only once)
var spatial_analysis = new SpatialAnalysis();
// save data
spatial_analysis.saveRumpleGrid('temp/rumple.asc');

Properties Overview

Name	Type	Description
`patchsizes`	`array`	The `patchsizes` property provides a list of with the number of pixels of each extracted patch in a prior call to See also: patches().
`rumpleIndex`	`double`	Retrieve the rumple index for the full landscape (i.e., one value).

Methods Overview

Method	Return Type	Description
`patches(grid, min_size)`	`void`	Perform a patch analysis on the input `grid` and return a Grid with unique patch IDs
`saveCrownCoverGrid(filename)`	`void`	Generate a map of the crown cover ( at 2m resolution), and save an average (100m) to `filename` (ESRI ASCII format).
`saveCrownCoverGrid(filename, mask)`	`void`	Generate a map of the crown cover ( at 2m resolution), and save an average to `filename` (ESRI ASCII format).
`saveRumpleGrid(filename)`	`void`	Calculate the Rumple-Index for the landscape with a spatial resolution of 10m (i.e., the cells of the iLand height grid)

Properties Details

`patchsizes`

array

The patchsizes property provides a list of with the number of pixels of each extracted patch in a prior call to See also: patches(). The first entry of the array is the number of pixels of the patch ID 1, etc.

`rumpleIndex`

double

Retrieve the rumple index for the full landscape (i.e., one value).

Methods Details

`patches(grid, min_size)`

Returns: void

Perform a patch analysis on the input grid and return a Grid with unique patch IDs assigned to each patch (starting with 1, 2, 3, …). A ‘patch’ is a number of adjacent pixels with a value > 0. In other words, all connected non-zero areas are flagged with unique Ids in the output grid. Internally, a simple flood-fill algorithm searching in the Moore-neighborhood (8 neighbors) is used and applied repeatedly.

If a patch has a size which is smaller than min_size, the cells of the grid are set to 0, and the patch is not recorded. A list of all patches (and patchsizes) is available with the patchsizes property.

`saveCrownCoverGrid(filename)`

Returns: void

Generate a map of the crown cover ( at 2m resolution), and save an average (100m) to filename (ESRI ASCII format). For each tree, the tree crown (as defined by the ‘reader’ stamp, which defines for 2m pixels the share of pixels that are covered by the crown) is additively plotted on a 2m grid. If that sum is larger then 0.5 (i.e. 50%), a pixel is consiedered as ‘covered’. The resulting grid provides for each 100m cell a fraction of ‘covered’ pixels. Note that 2m cells that are out of the project area are not counted (i.e., the resulting crown cover refers only to the stockable area of the resource unit).

Parameters:

filename (string): target filename (relative to project folder)

`saveCrownCoverGrid(filename, mask)`

Returns: void

Generate a map of the crown cover ( at 2m resolution), and save an average to filename (ESRI ASCII format). For each tree, the tree crown (as defined by the ‘reader’ stamp, which defines for 2m pixels the share of pixels that are covered by the crown) is additively plotted on a 2m grid. If that sum is larger then 0.5 (i.e. 50%), a pixel is consiedered as ‘covered’. The grid is used as a mask: the resulting grid uses the cell size of grid and also the spatial extent. The resulting grid provides for each 100m cell a fraction of ‘covered’ pixels.

Parameters:

filename (string): target filename (relative to project folder)
mask (Grid): (a Grid

Example:

// create a grid:
    var mask = new Grid();
    mask.create(100, 60, 10); // cell-size 10m, 100 x 60 cells
    mask.setOrigin(100,1020); // define the origin, the grid covers (100/1020)-(1100/1620)
    SpatialAnalysis.saveCrownCoverGrid('temp/test.asc', mask); // save the crown cover grid

`saveRumpleGrid(filename)`

Returns: void

Calculate the Rumple-Index for the landscape with a spatial resolution of 10m (i.e., the cells of the iLand height grid) and extract a 100m grid (average over the 10m cells). Store the grid to filename (ESRI ASCII format).

The Rumple-Index is a spatial index relating surface area to ground area. In forestry, it is a indicator of vertical heterogeneity. In iLand, the Rumple Index is the variability of the maximum tree height on 10m level (i.e. the “Height”-Grid). The RumpleIndex is calculated for each resource unit and also for the full project area.