urbanflow.utils.grid_utils¶

grid_utils.py

Utilities for combining and reading GeoPandas files, or applying operations on the grid

Functions

`cell_to_polygon`(row, col, transform)	Convert a raster cell index to its polygon footprint in spatial coordinates.
`instantiate_grid_and_transform`(cell_size, gdfs)	Instantiate a raster grid and affine transform covering the extent of given geometries.
`rasterize_geoms`(geoms, value, out, transform)	Rasterize geometries into an existing array (in-place).

urbanflow.utils.grid_utils.cell_to_polygon(row, col, transform)¶

Convert a raster cell index to its polygon footprint in spatial coordinates.

Parameters:

row (int) – Row index of the cell.
col (int) – Column index of the cell.
transform (affine.Affine) – Affine transform mapping raster indices to spatial coordinates.

Returns:

polygon – Polygon representing the spatial footprint of the cell.

Return type:

shapely.geometry.Polygon

Examples

>>> transform = Affine(1, 0, 0, 0, -1, 2)  # 1x1 cells
>>> cell_to_polygon(0, 0, transform).bounds
(0.0, 1.0, 1.0, 2.0)

urbanflow.utils.grid_utils.instantiate_grid_and_transform(cell_size, gdfs, default_grid_value=0)¶

Instantiate a raster grid and affine transform covering the extent of given geometries.

Parameters:

cell_size (float) – Resolution of grid cells in coordinate units (e.g., meters).
gdfs (geopandas.GeoDataFrame or sequence of GeoDataFrame) – One or more GeoDataFrames whose geometries define the spatial extent of the grid.
default_grid_value (int, optional) – Initial value used to fill all cells, by default 0.

Returns:

grid (ndarray of uint8, shape (rows, cols)) – Raster grid array initialized with default_grid_value.
transform (affine.Affine) – Affine transform mapping raster indices (row, col) to spatial coordinates.

Return type:

Tuple[ndarray[tuple[Any, …], dtype[uint8]], Affine]

Notes

The grid extent is snapped to whole multiples of cell_size so that the grid completely covers the union of input bounds.
The origin of the transform is the upper-left corner.

urbanflow.utils.grid_utils.rasterize_geoms(geoms, value, out, transform)¶

Rasterize geometries into an existing array (in-place).

Parameters:

geoms (iterable of shapely.geometry.BaseGeometry) – Geometries to rasterize.
value (int) – Integer value to burn into cells touched by the geometries.
out (ndarray) – Target raster array that will be modified in place.
transform (affine.Affine) – Affine transform mapping raster indices (row, col) to spatial coordinates.

Notes