how to start with geotiffs

[LukaszKowalski2013]

Hi,

I have a fairly simple task, but I don't know how to do it with your library even after reading examples.

I want to read a geotiff with your library. Multiply every value by 0 and save it to the same file. Later on I want to change it to polygon, so I have boundaries of the raster.

Can you help me with this?

[brendancol]

Hi @LukaszKowalski2013,

xarray-spatial doesn't do file I/O, it's only the spatial analytics (slope, hillshade, etc.). For reading and writing GeoTIFFs you want rioxarray:

import rioxarray

da = rioxarray.open_rasterio("your_file.tif")
da_zeroed = da * 0
da_zeroed.rio.to_raster("your_file.tif")

To get the raster boundary as a polygon, use rasterio.features.shapes:

import numpy as np
from shapely.geometry import shape
import rasterio
from rasterio.features import shapes

with rasterio.open("your_file.tif") as src:
    mask = src.read(1)
    binary = (mask != src.nodata).astype(np.uint8) if src.nodata is not None else np.ones_like(mask, dtype=np.uint8)
    
    results = list(shapes(binary, transform=src.transform))
    polygons = [shape(geom) for geom, val in results if val == 1]

Or if you just need the bounding box:

from shapely.geometry import box

with rasterio.open("your_file.tif") as src:
    bbox = box(*src.bounds)