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SarPy

SarPy is a basic Python library to read, write, display, and do simple processing of complex SAR data using the NGA SICD format. It has been released by NGA to encourage the use of SAR data standards throughout the international SAR community. SarPy complements the SIX library (C++) and the MATLAB SAR Toolbox, which are implemented in other languages but have similar goals.

Some sample SICD files can be found here.

In addition to SICD, SarPy can also read COSMO-SkyMed, RADARSAT-2, Radar Constellation Mission (RCM), and Sentinel-1 SLC formats and convert them to SICD.

Some examples of how to read complex SAR data using SarPy are provided in docs/sarpy_example.py.

Origins

SarPy was developed at the National Geospatial-Intelligence Agency (NGA). The software use, modification, and distribution rights are stipulated within the MIT license.

Dependencies

The core library functionality depends only on numpy >= 1.11.0 with some minor dependency on scipy.

Optional Dependencies and Behavior

There are a small collection of dependencies representing functionality which may not be core requirements for much of the sarpy targeted tasks. The tension between requiring the least extensive list of dependencies possible for core functionality and not having surprise unstated dependencies which caused unexpected failures is evident here. It is evident that there are many viable arguments for making any or all of these formally stated dependencies. The choices made here are guided by practical realities versus what is generally considered best practices.

For all packages on this list, the import is tried (where relevant), and any import errors fr these optional dependencies are caught and handled. In other words, a missing optional dependency will not be presented as import time. Excepting the functionality requiring h5py, this import error handling is probably silent.

Every module in sarpy can be successfully imported, provided that numpy and scipy are in the environment. Attempts at using functionality depending on a missing optional dependency will generate an error at run time with accompanying message indicating the missing optional dependency.

  • Use from Python 2.7 requires the typing package.

  • Support for reading single look complex data from certain sources which provide data in hdf5 format require the h5py package, this includes Cosmo-Skymed, ICEYE, and NISAR data.

  • Reading an image segment in a NITF file using jpeg or jpeg 2000 compression and/or writing a kmz image overlay requires the pillow package.

  • CPHD consistency checks, presented in the sarpy.consistency module, depend on lxml>=4.1.1, networkx>=2.5, shapely>=1.6.4, and pytest>=3.3.2. Note that these are the versions tested for compliance.

  • Some less commonly used (in the sarpy realm) NITF functionality requires the use and interpretation of UTM coordinates, and this requires the pyproj package.

  • Building sphinx documentation (mentioned below) requires packages sphinx, sphinxcontrib-napoleon, and sphinx_gallery.

  • Optional portions of running unit tests (unlikely to be of relevance to anyone not performing development on the core sarpy package itself) require the lxml package

Python 2.7

As mentioned above, using sarpy in Python 2.7 requires the typing package, easily installed using conda or pip. The development for sarpy has been geared towards Python 3.6 and above, but efforts have been made towards remaining compatible with Python 2.7.

Installation

From PyPI, install using pip (may require escalated privileges e.g. sudo):

pip install sarpy

Note that here pip represents the pip utility for the desired Python environment.

From the top level of a cloned version of this repository, install for all users of your environment (may require escalated privileges, e.g. sudo):

python setup.py install

Again, python here represents the executible associated with the desired Python environment.

For more verbose instructions for installing from source, such as how to perform an install applicable for your user only and requiring no escalated privileges, see here.

Documentation

As of version 1.1.76, documentation for the project is available at readthedocs.

If this documentation is inaccessible, it can be built locally after checking out this repository using sphinx via the command python setup.py build_sphinx. This depends on python packages sphinx and sphinxcontrib-napoleon.

Issues and Bugs

The core sarpy functionality has been tested for Python 2.7.17, 3.6, 3.7, 3.8, and 3.9. Other versions should be considered unsupported. Changes to sarpy for the sole purpose of supporting a Python version beyond end-of-life are unlikely to be considered.

Information regarding any discovered bugs would be greatly appreciated, so please feel free to create a github issue. If more appropriate, do not hesitate to contact [email protected] for assistance.

Pull Requests

Efforts at direct contribution to the project are certainly welcome, and please feel free to make a pull request. Note that any and all contributions to this project will be released under the MIT license.

Software source code previously released under an open source license and then modified by NGA staff is considered a "joint work" (see 17 USC 101); it is partially copyrighted, partially public domain, and as a whole is protected by the copyrights of the non-government authors and must be released according to the terms of the original open source license.

Associated GUI Capabilities moved to individual repositories - June 2020

In addition to a complete refactor of the core capabilities, graphical user interface functionality were first introduced in March 2020. In June 2020, these capabilities were split out of the sarpy repository into their own repositories in the NGA project. See the sarpy_apps, which depends on tk_builder.