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A deprecation warning is raised from the transform property and an affine property is added to provide the new feature. For method and function arguments, we sniff out GDAL geotransforms and try to do the right thing with them, also raising deprecation warnings in these cases.
65 lines
2.5 KiB
ReStructuredText
65 lines
2.5 KiB
ReStructuredText
Reprojection
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============
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Rasterio can map the pixels of a destination raster with an associated
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coordinate reference system and transform to the pixels of a source image with
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a different coordinate reference system and transform. This process is known as
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reprojection.
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Rasterio's ``rasterio.warp.reproject()`` is a very geospatial-specific analog
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to SciPy's ``scipy.ndimage.interpolation.geometric_transform()`` [1]_.
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The code below reprojects between two arrays, using no pre-existing GIS
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datasets. ``rasterio.warp.reproject()`` has two positional arguments: source
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and destination. The remaining keyword arguments parameterize the reprojection
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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 import Affine as A
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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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rows, cols = src_shape = (512, 512)
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d = 1.0/240 # decimal degrees per pixel
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# The following is equivalent to
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# A(d, 0, -cols*d/2, 0, -d, rows*d/2).
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src_transform = A.translation(-cols*d/2, rows*d/2) * A.scale(d, -d)
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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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