flexurba (version 0.2.3)

DoU_get_optimal_builtup: Get the optimal built-up area threshold

Description

In Data Package 2023, the Degree of Urbanisation includes a "Reduce Fragmentation Option" to account for the presence of office parks, shopping malls, factories and transport infrastructure. When the setting is enabled, urban centres are created using both cells with a population density of at least 1500 inhabitants per km² and cells that have an "optimal" built-up area on permanent land. This function can be used to determine this "optimal" threshold value.

The optimal threshold is dynamically identified as the global average built-up area proportion in clusters with a density of at least 1500 inhabitants per permanent land with a minimum population of 5000 people. We empirically discovered that the Degree of Urbanisation uses the rounded up (ceiled) optimal threshold to two decimal places.

For more information: see GHSL Data Package 2023, footnote 30. The arguments of the function allow to adapt the standard specifications in order to determine an alternative "optimal" threshold.

Usage

DoU_get_optimal_builtup(
  data,
  density_threshold = 1500,
  size_threshold = 5000,
  directions = 4
)

Value

optimal built-up area threshold

Arguments

data

path to the directory with the data, or named list with the data as returned by function DoU_preprocess_grid(). Ideally, it contains data on a global scale.

density_threshold

numeric. Minimum population density per permanent land

size_threshold

numeric. Minimum population size

directions

integer. Which cells are considered adjacent: 4 for rooks case (horizontal and vertical neighbours) or 8 for queens case (horizontal, vertical and diagonal neighbours)

Examples

data_belgium <- DoU_load_grid_data_belgium()

# determine the optimal built-up threshold with standard specifications
DoU_get_optimal_builtup(data_belgium)

# determine the optimal built-up threshold with custom specification
DoU_get_optimal_builtup(data_belgium,
  density_threshold = 1000,
  size_threshold = 3500,
  directions = 8
)