tessera

Tessera Embeddings Skill

Work with TESSERA satellite embeddings via the geotessera CLI, the Python library, or the R library.

What this skill is for

Use this skill when the user needs to:

• check where TESSERA embeddings exist
• download embeddings for a bbox or region file
• sample embeddings at point locations (Python/R library)
• build mosaics for dense raster analysis (Python library)
• choose between GeoTIFF, NPY, and Zarr output
• configure registry and cache behavior
• preview or serve downloaded outputs locally

Install

pip install geotessera                              # Python library + CLI

remotes::install_github("lassa-sentinel/GeoTessera") # R library

Key concepts

• embeddings are 128-channel dense vectors at 10m resolution per pixel
• tiles are 0.1° × 0.1° (~11km × 11km), stored as quantized int8 + float32 scales
• the Parquet registry (~few MB) is cached locally; tiles are fetched on demand
• all high-level API methods return dequantized float32 arrays
• hash verification is enabled by default

Points vs mosaics — choose the right approach

Prefer sample_embeddings_at_points() for most tasks. It only downloads the tiles it needs and returns a compact (N, 128) array. Use it for labeled site extraction, validation, sparse classification, and any workflow where you have specific coordinates.

Use fetch_mosaic_for_region() only when you need dense per-pixel coverage — e.g. wall-to-wall land cover classification or spatial clustering over a contiguous area. Mosaics merge and reproject all tiles in a bbox into a single large array, which is memory-intensive for large regions.

Have specific point locations?
  YES → sample_embeddings_at_points()
  NO  → Need wall-to-wall raster output?
          YES → fetch_mosaic_for_region()
          NO  → CLI download + export

Python library

from geotessera import GeoTessera

gt = GeoTessera()  # uses default registry and current directory

# --- Point sampling (preferred for most tasks) ---
points = [(0.15, 52.05), (0.25, 52.15), (-1.3, 51.75)]
embeddings = gt.sample_embeddings_at_points(points, year=2024)
# Returns: (N, 128) float32 array, NaN for missing points

# With metadata (tile info, pixel coordinates, CRS)
embeddings, metadata = gt.sample_embeddings_at_points(
    points, year=2024, include_metadata=True
)

# --- Mosaic (dense raster analysis only) ---
bbox = (-0.2, 51.4, 0.1, 51.6)
mosaic, transform, crs = gt.fetch_mosaic_for_region(bbox, year=2024)
# Returns: (H, W, 128) float32 array

# --- Single tile ---
embedding, crs, transform = gt.fetch_embedding(lon=0.15, lat=52.05, year=2024)
# Returns: (H, W, 128) float32, CRS, Affine transform

# --- Export ---
gt.export_embedding_geotiff(lon=0.15, lat=52.05, output_path="tile.tif", year=2024)
gt.export_embedding_zarr(lon=0.15, lat=52.05, output_path="tile.zarr", year=2024)

# --- Registry queries ---
gt.registry.get_available_years()           # [2017, 2018, ..., 2025]
gt.registry.get_tile_counts_by_year()       # {2024: 1234567, ...}
tiles = gt.registry.load_blocks_for_region(bounds=bbox, year=2024)

Point inputs accept list of (lon, lat) tuples, GeoJSON FeatureCollections, or GeoPandas GeoDataFrames.

R library

An R port by Simon Frost (Microsoft Research). Uses R6 classes, sf, terra, and arrow.

remotes::install_github("lassa-sentinel/GeoTessera")
library(GeoTessera)

gt <- geotessera()
tiles <- gt$get_tiles(bbox = c(-0.2, 51.4, 0.1, 51.6), year = 2024)
gt$export_embedding_geotiffs(tiles = tiles, output_dir = "london_tiles")

Full R docs: https://lassa-sentinel.github.io/GeoTessera

CLI workflow

1. Check coverage first

geotessera coverage --output coverage_map.png
geotessera coverage --year 2024 --country uk

2. Download for a region

geotessera download --bbox "-0.2,51.4,0.1,51.6" --year 2024 --output ./tiffs
geotessera download --region-file cambridge.geojson --year 2024 --output ./tiffs

3. Pick output format

geotessera download --bbox "..." --format tiff --year 2024 --output ./tiffs  # GIS-ready
geotessera download --bbox "..." --format npy  --year 2024 --output ./arrays # ML-friendly
geotessera download --bbox "..." --format zarr --year 2024 --output ./zarr   # cloud-native

4. Select bands if needed

geotessera download --bbox "..." --bands "0,1,2" --year 2024 --output ./subset

5. Visualize or serve

geotessera visualize ./tiffs --type web --output ./web
geotessera serve ./web --open

Tips

• prefer sample_embeddings_at_points() over mosaics for sparse locations
• prefer coverage before large CLI downloads
• use --format tiff for GIS-ready outputs, --format npy for array-first ML
• use --bands to reduce output size when only a few channels are needed
• keep --year explicit — data is available from 2017 to 2025
• use a fixed registry path or URL for reproducibility

Common mistakes

Mistake	Fix
Building a mosaic just to extract a few points	Use sample_embeddings_at_points() instead
Downloading all 128 bands when only a few are needed	Use --bands (CLI) or the bands parameter
Not checking coverage before a large download	Run geotessera coverage first
Forgetting --year and getting default year	Always specify --year explicitly

References

• references/geotessera-cli.md — full CLI flag reference
• references/geotessera-library.md — Python library API reference