NZ STAC

Find datasets and Cloud Optimised GeoTIFF (COG) tile URLs in LINZ's public nz-elevation, nz-imagery, and nz-coastal AWS buckets, hosted in ap-southeast-2. Python 3.10+, stdlib only; no AWS credentials, boto3, or LINZ Data Service key. Coastal commands return collection metadata and COG hrefs only. They do not download DEM or DSM rasters.

Workflow

1. Run collections with the bucket kind and optional region. Copy the returned collection selector (kind plus published path), or use its HTTPS collection.json URL. info returns the upstream STAC id and full metadata.
2. Check capture interval, product and resolution with info. DEM represents terrain; DSM includes surface features. Use the source capture dates for freshness, rather than its processing/update date.
3. Use a small WGS84 bbox to find tiles. --format geojson emits a FeatureCollection of the actual STAC footprints. Assets are public HTTPS COG URLs. The helper fetches bounded JSON metadata only, never raster files.
4. For a terrain point, use an elevation DEM collection with point. Coastal collections are not accepted there. It returns sampling_status=sampling_required, elevation=null, the tile URL and a gdallocationinfo one-liner. Run that command with GDAL installed to sample remotely by HTTP range reads. Check nodata and the source vertical datum. The stdlib helper does not decode compressed GeoTIFFs or report an invented elevation. A tile footprint may contain nodata.

Commands

Run from the repository root, or use an absolute path to scripts/cli.py.

python3 skills/nz-stac/scripts/cli.py collections --kind elevation --region auckland --json
python3 skills/nz-stac/scripts/cli.py collections --kind imagery --region auckland --json
python3 skills/nz-stac/scripts/cli.py collections --kind coastal --region auckland --limit 20 --json
python3 skills/nz-stac/scripts/cli.py info coastal:auckland/mangawhai-to-snells_2025/dem_1m/2193 --json
python3 skills/nz-stac/scripts/cli.py tiles coastal:auckland/mangawhai-to-snells_2025/dem_1m/2193 --bbox 174.59,-36.01,174.60,-36.00 --limit 5 --json
python3 skills/nz-stac/scripts/cli.py info elevation:auckland/auckland-part-1_2024/dem_1m/2193 --json
python3 skills/nz-stac/scripts/cli.py tiles elevation:auckland/auckland-part-1_2024/dsm_1m/2193 --bbox 174.715,-36.905,174.725,-36.895 --json
python3 skills/nz-stac/scripts/cli.py tiles elevation:auckland/auckland-north_2016-2018/dem_1m/2193 --bbox 174.715,-36.905,174.725,-36.895 --format geojson
python3 skills/nz-stac/scripts/cli.py tiles imagery:auckland/auckland_2024_0.075m/rgb/2193 --bbox 174.715,-36.905,174.725,-36.895 --format geojson
python3 skills/nz-stac/scripts/cli.py tiles imagery:auckland/auckland_2024_0.075m/rgbnir/2193 --bbox 174.715,-36.905,174.725,-36.895 --limit 5 --json
python3 skills/nz-stac/scripts/cli.py point --lon 174.72 --lat -36.9 --collection elevation:auckland/auckland-part-1_2024/dem_1m/2193 --json

Every data command supports --json; tiles and point also support --format geojson. Human output is the default.

Bounds and interpretation

• --bbox is minLon,minLat,maxLon,maxLat. Longitude comes first. Tile search supports mainland NZ Topo50 tile names in EPSG:2193; unsupported grids fail clearly. Chatham Islands need a different CRS.
• Collections default to 100 records, capped at 200 per request. Use --offset and --limit for another slice. matched is the catalogue count after region filtering. The coastal catalogue has more collections than the default page, so an unfiltered coastal listing is truncated. Listings derive year, resolution and product from published names and paths; licence is null until info or tile metadata supplies it. Hillshade paths stay unknown rather than DEM or DSM.
• point accepts elevation DEM and DSM collections only. A coastal selector is rejected. Use tiles for coastal COG hrefs. OpenAerialMap and Copernicus GFM are different publishers and are not kinds of this skill.
• Tile results default to 20, capped at 50. At most 100 nearby item JSON files are candidates; a larger bbox fails with a request to narrow it. truncated means at least one additional matching footprint exists. Results include candidates and items_inspected; there is no unbounded item crawl.
• JSON envelopes and records carry source_url, publisher, licence, retrieved_at (UTC) and latest_data (capture end, or the catalogue title's stated year range). Unknown metadata stays null.
• point returns all discovered touching tiles up to four, with an explicit truncation flag. no_tile means no intersecting tile in that collection. It does not mean the location has no elevation in other collections.

Read references/source-notes.md for the static STAC schema, tile-grid method, exact Auckland selectors and source limits. Verify the skill with scripts/test_contract.py (deterministic fixtures) and scripts/smoke_test.py (bounded live Auckland probes and 16-byte COG ranges).