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🌍 xarray-spatial: Raster-Based Spatial Analysis in Python

Build Status Build status PyPI version

title

πŸ“ Fast, Accurate Python library for Raster Operations

⚑ Extensible with Numba

⏩ Scalable with Dask

🎊 Free of GDAL / GEOS Dependencies

🌍 General-Purpose Spatial Processing, Geared Towards GIS Professionals


Xarray-Spatial implements common raster analysis functions using Numba and provides an easy-to-install, easy-to-extend codebase for raster analysis.

Installation

# via pip
pip install xarray-spatial

# via conda
conda install -c conda-forge xarray-spatial

xarray-spatial grew out of the Datashader project, which provides fast rasterization of vector data (points, lines, polygons, meshes, and rasters) for use with xarray-spatial.

xarray-spatial does not depend on GDAL / GEOS, which makes it fully extensible in Python but does limit the breadth of operations that can be covered. xarray-spatial is meant to include the core raster-analysis functions needed for GIS developers / analysts, implemented independently of the non-Python geo stack.

Our documentation is still under constructions, but docs can be found here.

Raster-huh?

Rasters are regularly gridded datasets like GeoTIFFs, JPGs, and PNGs.

In the GIS world, rasters are used for representing continuous phenomena (e.g. elevation, rainfall, distance), either directly as numerical values, or as RGB images created for humans to view. Rasters typically have two spatial dimensions, but may have any number of other dimensions (time, type of measurement, etc.)

Supported Spatial Functions

Name / Module xr.DataArary Support xr.Dataset Support GPU Support (CUDA) Dask Support
Aspect / aspect.py YES NO YES
Bump Mapping / bump.py YES NO NO
Equal Interval / classify.py YES NO NO
Natural Breaks / classify.py YES NO NO
Reclassify / classify.py YES NO NO
Quantile / classify.py YES NO NO
Curvature / curvature.py YES NO NO
Apply / focal.py YES NO NO
Hotspots / focal.py YES NO NO
Mean / focal.py YES NO NO
Focal Statistics / focal.py YES NO YES
Hillshade / hillshade.py YES NO NO
Atmospherically Resistant Vegetation Index (ARVI) / multispectral.py YES NO YES
Enhanced Built-Up and Bareness Index (EBBI) / multispectral.py YES NO YES
Enhanced Vegetation Index (EVI) / multispectral.py YES NO YES
Green Chlorophyll Index (GCI) / multispectral.py YES NO YES
Normalized Burn Ratio (NBR) / multispectral.py YES NO YES
Normalized Burn Ratio 2 (NBR2) / multispectral.py YES NO YES
Normalized Difference Moisture Index (NDMI) / multispectral.py YES NO YES
Normalized Difference Vegetation Index (NDVI) / multispectral.py YES NO YES
Soil Adjusted Vegetation Index (SAVI) / multispectral.py YES NO YES
Structure Insensitive Pigment Index (SIPI) / multispectral.py YES NO YES
Pathfinding / pathfinding.py YES NO NO
Perlin Noise / perlin.py YES NO NO
Allocation / proximity.py YES NO NO
Direction / proximity.py YES NO NO
Proximity / proximity.py YES NO NO
Slope / slope.py YES NO YES
Terrain Generation / terrain.py YES NO NO
Viewshed / viewshed.py YES NO NO
Apply / zonal.py YES NO NO
Crop / zonal.py YES NO NO
Regions / zonal.py YES NO NO
Trim / zonal.py YES NO NO
Zonal Statistics / zonal.py YES NO NO
Zonal Cross Tabulate / zonal.py YES NO NO

Usage

Basic Pattern
import xarray as xr
from xrspatial import hillshade

my_dataarray = xr.DataArray(...)
hillshaded_dataarray = hillshade(my_dataarray)

Check out the user guide here.


title title

Dependencies

xarray-spatial currently depends on Datashader, but will soon be updated to depend only on xarray and numba, while still being able to make use of Datashader output when available.

title

Notes on GDAL

Within the Python ecosystem, many geospatial libraries interface with the GDAL C++ library for raster and vector input, output, and analysis (e.g. rasterio, rasterstats, geopandas). GDAL is robust, performant, and has decades of great work behind it. For years, off-loading expensive computations to the C/C++ level in this way has been a key performance strategy for Python libraries (obviously...Python itself is implemented in C!).

However, wrapping GDAL has a few drawbacks for Python developers and data scientists:

  • GDAL can be a pain to build / install.
  • GDAL is hard for Python developers/analysts to extend, because it requires understanding multiple languages.
  • GDAL's data structures are defined at the C/C++ level, which constrains how they can be accessed from Python.

With the introduction of projects like Numba, Python gained new ways to provide high-performance code directly in Python, without depending on or being constrained by separate C/C++ extensions. xarray-spatial implements algorithms using Numba and Dask, making all of its source code available as pure Python without any "black box" barriers that obscure what is going on and prevent full optimization. Projects can make use of the functionality provided by xarray-spatial where available, while still using GDAL where required for other tasks.

Contributors

  • @brendancol
  • @thuydotm
  • @jbednar
  • @pablomakepath
  • @kristinepetrosyan
  • @sjsrey
  • @giancastro
  • @ocefpaf
  • @rsignell-usgs
  • @marcozimmermannpm
  • @jthetzel
  • @chase-dwelle

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