CODEWITHSUNDEEP
pythoncoordinatesshapelyrasterio
Judith
Judith

Reputation: 167

Creating polygons using rasterio and shapely based on a lon, lat and an array of 0's and 1's

I have an numpy array with 0 and 1's. I am trying to convert the 1's into polygons. I have managed to do so using rasterio and shapely as seen in the code below:

im = np.array([[0, 0, 0, 0, 0],
   [0, 1, 1, 1, 0],
   [0, 0, 1, 0, 0],
   [0, 1, 1, 1, 0],
   [0, 0, 0, 0, 0]])
shapes = rasterio.features.shapes(im)
polygons = [shapely.geometry.Polygon(shape[0]["coordinates"][0]) for shape in shapes if shape[1] == 1]
print(polygon[0])

however, each row and column reffers to longitude and latitude coordinates stored in different arrays. for example:

lon = np.array([125.  , 125.25, 125.5 , 125.75, 126.  ])
lat = np.array([-35.  , -35.25, -35.5 , -35.75, -36.  ])

Does anyone know how to create the polygons associated with the correct coordinates? I think I have to use the transform parameter of the rasterio.features.shapes function. Yet I haven't been able to figure it out yet.

Upvotes: 1

Views: 1059

Answers (1)

Judith
Judith

Reputation: 167

Found the solution. The transform parameter indeed is needed. This parameter is and affine trasnformation which is defined as:

xres = (max(lon) - min(lon))/len(lon)
yres = (lat[-1] - lat[0])/len(lat)

transform1 = Affine.translation(min(lon) - xres / 2, lat[0] - yres / 2) * Affine.scale(xres, yres)

that can be used to create the polygons with rasterio and shapely

shapes = rasterio.features.shapes(im, transform = transform1)
polygons = [shapely.geometry.Polygon(shape[0]["coordinates"][0]) for shape in shapes if shape[1] == 1]

Upvotes: 1

Related Questions