burst2safe 0.4.1

A package for converting ASF-derived Sentinel-1 burst SLC products to the ESA SAFE format

burst2safe

Utility for converting ASF-derived Sentinel-1 burst SLC products to the ESA SAFE format.

This is still a work in progress, and we recommend waiting until the release of version 1.0.0 for use in production environments!

Setup

Installation

To use the tool, install it via pip:

pip install burst2safe

Or conda:

conda install -c conda-forge burst2safe

Credentials

To use burst2safe, you must provide your Earthdata Login credentials via two environment variables (EARTHDATA_USERNAME and EARTHDATA_PASSWORD), or via your .netrc file.

If you do not already have an Earthdata account, you can sign up here.

If you would like to set up Earthdata Login via your .netrc file, check out this guide to get started.

burst2safe usage

The burst2safe command line tool can be run using the following structure:

burst2safe --orbit 32861 --extent 53.57 27.54 53.78 27.60

Where:

• --orbit is the absolute orbit number of the Sentinel-1 data.
• --extent is the area of interest as a bounding box in the format minlon minlat maxlon maxlat or as a path to a GDAL-compatible vector file.

You can specify the --pols argument to select the desired polarizations to include. The options are VV, VH, HV, and HH. The default is VV.

You can specify the --swaths argument to select the desired swaths to include. The options are IW1, IW2, and IW3. The default is to include all swaths.

You can also specify a minimum number of bursts per polarization/swath combination using the --min-bursts argument. The --min-bursts argument is useful for workflows that require a minimum number of bursts, such as Enhanced Spectral Diversity (ESD) processing within InSAR processing chains.

For more control over the burst group, you can also provide specific burst granule IDs to be merged into a SAFE file using the following structure:

burst2safe S1_136231_IW2_20200604T022312_VV_7C85-BURST S1_136232_IW2_20200604T022315_VV_7C85-BURST

This search is equivalent to the previous search. To be eligible for processing, all burst granules must:

1. Have the same acquisition mode
2. Be from the same absolute orbit
3. Be contiguous in time and space.
4. Have the same footprint for all polarizations.

The tool should raise an error if any of these conditions are not met.

The output SAFE file will be created in the directory specified using the --output-dir argument, which defaults to the current directory.

burst2stack usage

For those who want to create stacks of SAFEs (SAFEs covering the same region but from different dates), we have created the burst2stack tool. This tool has a similar structure as burst2safe, but with small changes to the CLI arguments.

This includes:

• Exclusion of the granules pathway
• Specifying the relative instead of absolute orbit number
• Adding a start date and end date argument

An example command that runs burst2stack for the same area as the previous examples, but for a range of dates can be seen below:

burst2stack --rel-orbit 64 --start-date 2020-06-03 --end-date 2020-06-17 --extent 53.57 27.54 53.78 27.60

The usage of the --extent, --pols, --swaths, and --min-bursts arguments is the same as in burst2safe.

Strategy

burst2safe combines and reformats individual bursts into a SAFE file following the procedure described in the Sentinel-1 Product Specification Document In this document, ESA describes how to create an Assembled Sentinel-1 Level 1 product from individual Sentinel-1 Level 1 SAFEs. We use this same strategy to combine ASF-extracted burst SLC products into a SAFE file that should be compatible with any SAR processor currently capable of using Sentinel-1 Level SAFEs. For in-depth technical details of the implementation, we refer you to the Sentinel-1 Product Specification document above. However, it is important to know that ESA recommends merging Sentinel-1 data/metadata components using three primary strategies:

Include

A given data/metadata component is the same for all data slices, and any value can be used (i.e., polarization).

For Include components, the value associated with the earliest burst is always used.

Concatenate

A given data/metadata component is a series of time-ordered fields that can be combined into a single list (i.e., ground control points).

For Concatenate components, the fields are merged and subset to the start/stop times of the included bursts. Where present line sub-fields have also been updated.

Merge

A given data/metadata component must be recalculated using a process unique to each component (i.e., platform heading).

For Merge components, we have made the best effort to follow the merging instructions outlined in the product specification. While we hope to eventually correctly reconstruct all merged fields, there are some components for whom the implementation is unclear. In these cases, we have set the values of these fields to NULL ('') so that downstream processors raise errors instead of using incorrect values. If any fields we have omitted in this way cause your application to fail, let us know so that we can prioritize its development!

Deviations from Specification

In some cases, we were not able to recreate certain datasets or metadata fields in the exact way that the IPF computes them, because the creation process is unknown to us, or utilizes data that we do not have access to. This includes datasets such as all datasets in the SAFE preview directory the SAFE report PDF included with each SAFE file, some metadata fields in the annotation datasets.

A full accounting of omitted datasets and differing fields can be found below:

• Annotation
  • Noise
    • No intentional omissions or deviations.
  • Calibration
    • No intentional omissions or deviations
  • RFI
    • No intentional omissions or deviations.
  • Product
    • generalAnnotation/productInformation/platformHeading
      • calculated as average of input Level 1 SLCs, not recalculated from Level-0 slices.
    • imageAnnotation/imageInformation/azimuthPixelSpacing
      • calculated as average of input Level 1 SLCs, not Level-0 slices.
    • imageAnnotation/imageInformation/imageStatistics/outputDataMean / outputDataStdDev
      • calculated using np.mean/np.std on valid data.
• Measurement GeoTIFFs
  • Invalid data as denoted by swathTiming/burstList/burst/firstValidSample and lastValidSample are set to zero. This done by the ASF extractor, not this tool.
  • TIFF tags that are not GeoTIFF tags are omitted. See Product Specification Table 3-8 for full list.
• Preview
  • All preview datasets and the preview directory are omitted.
• Support
  • s1-product-preview.xsd, s1-map-overlay.xsd, s1-quicklook.xsd and are omitted.
• Manifest
  • metadataObjects associated with support datasets are omitted.
• SAFE report
  • The SAFE report PDF is omitted.

IPF Version Compatibility

At this time, we are not aware of any compatibility issues with older Sentinel-1 Instrument Processing Facility (IPF) versions. However, if you do encounter any incompatibilities please open an issue, so we can fix it!

EW SLC Compatibility

The tool is currently only compatible with the Sentinel-1 Interferometric Wide (IW) SLC data. If you would like to see support for Extra Wide (EW) SLC data, please open an issue!

Developer Setup

1. Ensure that conda is installed on your system (we recommend using mambaforge to reduce setup times).
2. Download a local version of the burst2safe repository (git clone https://github.com/forrestfwilliams/burst2safe.git)
3. In the base directory for this project call mamba env create -f environment.yml to create your Python environment, then activate it (mamba activate burst2safe)
4. Finally, install a development version of the package (python -m pip install -e .)

To run all commands in sequence use:

git clone https://github.com/forrestfwilliams/burst2safe.git
cd burst2safe
mamba env create -f environment.yml
mamba activate burst2safe
python -m pip install -e .

License

burst2safe is licensed under the BSD 2-Clause License. See the LICENSE file for more details.

Contributing

Contributions this project are welcome! If you would like to contribute, please submit a pull request on the GitHub repository.

Contact Us

Want to talk about burst2safe? We would love to hear from you!

Found a bug? Want to request a feature? open an issue

General questions? Suggestions? Or just want to talk to the team? chat with us on burst2safe's discussion page