satchip 0.2.0

A package for satellite image AI data prep

SatChip

A package for satellite image AI data prep. This package "chips" data labels and satellite imagery into 264x264 image arrays following the TerraMind extension of the MajorTom specification.

Usage

SatChip relies on a two-step process; chip your label train data inputs, then create corresponding chips for different remote sensing data sources.

Step 1: Chip labels

The chiplabel CLI tool takes a GDAL-compatible image, a collection date, and an optional output directory as input using the following format:

chiplabel PATH/TO/LABELS.tif DATE(UTC FORMAT) --outdir OUTPUT_DIR

For example:

chiplabel LA_damage_20250113_v0.tif 2024-01-01T01:01:01 --outdir chips

This will produce an output zipped Zarr store label dataset with the name {LABELS}.zarr.zip in the specified output directory (--outdir). This file will be the input to the remote sensing data chipping step.

For more information on usage see chiplabel --help

Step 2: Chip remote sensing data

The chipdata CLI tool takes a label zipped Zarr store, a dataset name, and an optional output directory as input using the following format:

chipdata PATH/TO/LABELS.zarr.zip DATASET --outdir OUTPUT_DIR

For example:

chipdata LA_damage_20250113_v0.zarr.zip S2L2A --outdir chips

Similarly to step 1, this will produce an output zipped Zarr store that contains chipped data for your chosen dataset with the name {LABELS}_{DATASET}.zarr.zip.

Currently support datasets include:

• S2L2A: Sentinel-2 L2A data sourced from the Sentinel-2 AWS Open Data Archive
• HLS: Harmonized Landsat Sentinel-2 data sourced from LP DAAC's Data Archive
• S1RTC: Sentinel-1 Radiometric Terrain Corrected (RTC) data created using ASF's HyP3 on-demand platform

Tiling Schema

This package chips images based on the TerraMesh grid system, which builds on the MajorTOM grid system.

The MajorTOM grid system provides a global set of fixed image grids that are 1068x1068 pixels in size. A MajorTOM grid can be defined for any tile size, but we fix the grid to 10x10 Km tiles. Tiles are named using the format:

ROW[U|D]_COL[L|R]

Where, ROW is indexed from the equator, with a suffix U (up) for tiles north of the equator and D (down) for tiles south of it, and COL is indexed from the prime meridian, with a suffix L (left) for tiles east of the prime meridian and R (right) for tiles west of it.

To support finer subdivisions, the TerraMesh grid system divides each MajorTOM grid into a 4x4 set of sub-tiles, each 264x264 pixels. The subgrid is centered within the parent tile, leaving a 6-pixel border around each sub-tile. Subgrid names extend the base format with two additional indices:

ROW[U|D]_COL[L|R]_SUBCOL_SUBROW

For instance, the bottom-left subgrid of MajorTOM tile 434U_876L is named 434U_876L_0_3. See the figure below for a visual description:

Viewing Chips

Assessing chips after their creation can be challenging due to the large number of small images created. To address this issue, SatChip includes a chipview CLI tool that uses Matplotlib to quickly visualize the data included within the created zipped Zarr stores:

chipview PATH/TO/CHIPS.zarr.zip BAND --idx IDX

Where PATH/TO/CHIPS.zarr.zip is the path to the chip file (labels or image data), BAND is the name of the band you would like to view, and IDX is an optional integer index of which dataset you would like to initially view.

License

SatChip is licensed under the BSD-3-Clause open source license. See the LICENSE file for more details.

Contributing

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