Total core area (Core area metric)

## Usage

lsm_l_tca(landscape, directions = 8, consider_boundary = FALSE, edge_depth = 1)

## Arguments

landscape

A categorical raster object: SpatRaster; Raster* Layer, Stack, Brick; stars or a list of SpatRasters.

directions

The number of directions in which patches should be connected: 4 (rook's case) or 8 (queen's case).

consider_boundary

Logical if cells that only neighbour the landscape boundary should be considered as core

edge_depth

Distance (in cells) a cell has the be away from the patch edge to be considered as core cell

tibble

## Details

$$TCA = \sum \limits_{j = 1}^{n} a_{ij}^{core} * (\frac{1} {10000})$$ where here $$a_{ij}^{core}$$ is the core area in square meters.

TCA is a 'Core area metric' and equals the sum of core areas of all patches in the landscape. A cell is defined as core area if the cell has no neighbour with a different value than itself (rook's case). In other words, the core area of a patch is all area that is not an edge. It characterises patch areas and shapes of all patches in the landscape simultaneously (more core area when the patch is large and the shape is rather compact, i.e. a square). Additionally, TCA is a measure for the configuration of the landscape, because the sum of edges increase as patches are less aggregated.

Because the metric is based on distances or areas please make sure your data is valid using check_landscape.

Hectares

TCA >= 0

### Behaviour

Increases, without limit, as patch areas increase and patch shapes simplify. TCA = 0 when every cell in every patch is an edge.

## References

McGarigal K., SA Cushman, and E Ene. 2023. FRAGSTATS v4: Spatial Pattern Analysis Program for Categorical Maps. Computer software program produced by the authors; available at the following web site: https://www.fragstats.org

lsm_p_core, lsm_c_tca
landscape <- terra::rast(landscapemetrics::landscape)