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59 lines
2.3 KiB
ReStructuredText
59 lines
2.3 KiB
ReStructuredText
Reprojection
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============
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Rasterio can map the pixels of a destination raster with an associated coordinate
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reference system and transform to the pixels of a source image with a different
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coordinate reference system and transform. This process is known as reprojection.
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Rasterio's ``rasterio.warp.reproject()`` is a very geospatial-specific analog to
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SciPy's ``scipy.ndimage.interpolation.geometric_transform()`` [1]_.
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The code below reprojects between two arrays, using no pre-existing GIS datasets.
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``rasterio.warp.reproject()`` has two positional arguments: source and destination.
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The remaining keyword arguments parameterize the reprojection transform.
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.. code-block:: python
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import numpy
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import rasterio
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from rasterio.warp import reproject, RESAMPLING
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with rasterio.drivers():
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# As source: a 512 x 512 raster centered on 0 degrees E and 0
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# degrees N, each pixel covering 15".
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src_shape = (512, 512)
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src_transform = [-256.0/240, 1.0/240, 0.0, 256.0/240, 0.0, -1.0/240]
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src_crs = {'init': 'EPSG:4326'}
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source = numpy.ones(src_shape, numpy.uint8)*255
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# Destination: a 1024 x 1024 dataset in Web Mercator (EPSG:3857)
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# with origin at 0.0, 0.0.
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dst_shape = (1024, 1024)
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dst_transform = [-237481.5, 425.0, 0.0, 237536.4, 0.0, -425.0]
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dst_crs = {'init': 'EPSG:3857'}
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destination = numpy.zeros(dst_shape, numpy.uint8)
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reproject(
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source,
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destination,
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src_transform=src_transform,
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src_crs=src_crs,
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dst_transform=dst_transform,
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dst_crs=dst_crs,
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resampling=RESAMPLING.nearest)
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# Assert that the destination is only partly filled.
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assert destination.any()
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assert not destination.all()
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See `examples/reproject.py <https://github.com/mapbox/rasterio/blob/master/examples/reproject.py>`__ for code that writes the destination array to a GeoTIFF file. I've
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uploaded the resulting file to a Mapbox map to demonstrate that the reprojection is
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correct: https://a.tiles.mapbox.com/v3/sgillies.hfek2oko/page.html?secure=1#6/0.000/0.033
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References
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----------
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.. [1] http://docs.scipy.org/doc/scipy/reference/generated/scipy.ndimage.interpolation.geometric_transform.html#scipy.ndimage.interpolation.geometric_transform
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