Creates regular hexagonal or square grids over a study area. The function automatically handles coordinate-system transformations and ensures proper grid alignment.
Usage
create_grid(
study_area,
cell_size,
type = c("hexagonal", "square"),
projection_crs = NULL,
id_column = NULL,
return_crs = 4326,
check_size = TRUE,
max_cells = 1e+06
)Arguments
- study_area
sf object containing polygonal geometries defining the study area. May be in any CRS.
- cell_size
Grid cell size (see Details for units).
- type
`"hexagonal"` (default) or `"square"`.
- projection_crs
CRS used for grid construction. Default `NULL` selects an appropriate UTM zone via [`get_utm_crs()`]. Pass an EPSG code or CRS string to override.
- id_column
Optional column name in `study_area` for creating separate grids per unique value. If supplied, returns a named list of grids.
- return_crs
CRS for the output grid (default WGS84). The grid is transformed to this CRS after creation.
- check_size
Whether to warn when the grid is very large (default TRUE).
- max_cells
Maximum number of cells allowed before stopping (default 1,000,000). Set to `NULL` to disable.
Value
sf object containing the grid (or named list of sf objects when `id_column` is given). Each grid cell carries `grid_id` and `grid_index`.
Details
**Cell size units depend on the projection CRS:** - Projected CRS (UTM, etc.): `cell_size` is in **metres**. - Geographic CRS (WGS84): `cell_size` is in **degrees**.
Use a projected CRS for real-world analysis. If `projection_crs` is `NULL` (the default), an appropriate UTM zone is chosen automatically using [`get_utm_crs()`].
Hexagons are pointy-topped; `cell_size` is the flat-to-flat distance (width between opposite edges).