$$CA = sum(AREA[patch_{ij}])$$
where \(AREA[patch_{ij}]\) is the area of each patch in hectares.
TA is an 'Area and edge metric'. The total (class) area sums the area of all patches
in the landscape. It is the area of the observation area.
Because the metric is based on distances or areas please make sure your data
is valid using check_landscape.
Behaviour
Approaches TA > 0 if the landscape is small and increases,
without limit, as the size of the landscape increases.