ERDAS LAN / AVIRIS (Indian Pines)

Status: Experimental · Vendor: ERDAS Imagine / AVIRIS (NASA JPL) · Extensions: .lan (+ .spc, .GIS sidecars)

ERDAS LAN is a banded raster container. This reader is scoped to the classic AVIRIS 92AV3C “Indian Pines” hyperspectral cube — a widely used benchmark — and is meant for validating hyperspectral dispatch and pixel-spectrum extraction, not as a general ERDAS Imagine reader.

Instruments & software

The supported file is the AVIRIS 92AV3C cube acquired over the Indian Pines test site and distributed in ERDAS LAN form. The accompanying .spc file is not Galactic SPC: it is an AVIRIS band-calibration text file listing the 220 band centres. The optional 92AV3GT.GIS file is the per-pixel ground-truth land-cover label map.

File structure

  • HEAD74 magic followed by a 128-byte ERDAS header (band count at offset 8, rows at 16, cols at 20, read as little-endian u32).

  • 145 rows × 145 columns × 220 bands of unsigned 16-bit little-endian samples in BIL (band-interleaved-by-line) order.

  • <stem>.spc sidecar — one band-centre wavelength per line (first whitespace token), skipping FILE and dashed separator lines. The native band order has local wavelength inversions, so the emitted axis order is non-monotonic.

  • 92AV3GT.GIS sidecar (optional) — a second HEAD74 raster of the same 145×145 footprint carrying the class label per pixel.

What nirs4all-formats extracts

  • Default layout — one SpectralRecord per pixel (21,025 records), each with a single raw_counts signal, a nm wavelength axis (unit dn), and metadata sample_id = pixel_y{row}_x{col}, x_index, y_index, spatial_x, spatial_y (= column / row), spatial_unit = "pixel", rows, cols, bands, interleave = "bil". When the .GIS sidecar is present, each record gains targets.land_cover_class.

  • Pixel selection — a half-open CubeWindow ROI (--rows START:END --cols START:END) or an ordered sparse CubeMask (--pixel ROW,COL / --pixels-file, duplicates preserved). The window mode works alongside the single-record cube; the mask mode does not.

  • Single-record mode — ReadOptions::single_record() / --single-record emits one N-dimensional record (dims = ["row", "col", "x"], shape = [rows, cols, bands]) with row/col index coordinates; the ground-truth labels are kept as a 2-D metadata.land_cover_class_grid (they do not fit the scalar-per-record targets shape — use the per-pixel layout for pixel-as-sample classification).

  • Provenance — the .lan primary, the .spc axis sidecar and (when present) the .GIS ground-truth, each with SHA-256. The first record carries the erdas_lan_aviris_experimental status warning (kept off the other 21,024 pixel records to avoid ~200 KiB of duplicated provenance; the erdas-lan-aviris format name carries the same signal), plus erdas_lan_spc_axis_non_monotonic_native_order when the .spc axis is out of order.

Variants & support status

Variant

Status

Notes

AVIRIS 92AV3C 145×145×220 ERDAS LAN

Experimental

Sole supported layout; strict refusal for any other dimensions.

Generic ERDAS Imagine / LAN

Planned

No general header parsing, data types or interleaves yet.

NEON / Specim / HySpex / Headwall / AVIRIS-NG cubes

Planned

HDF5 and raw cube layouts not covered.

Limitations & known gaps

  • Dimensions other than 145×145×220 are refused with a descriptive error.

  • The ground-truth filename is the literal 92AV3GT.GIS regardless of the LAN stem; a user-renamed ground-truth file would not be picked up (an intentional narrowing to the canonical Indian Pines layout).

  • No reference comparison against Spectral Python or rasterio yet.

Reference readers

The Indian Pines cube is commonly read with Spectral Python (spectral), rasterio and SciPy. A subprocess conformance comparison is not yet wired in.

Samples & validation

Fixtures live under samples/hyperspectral_cubes/: 92AV3C.lan (21,025 pixel records, 220-point nm axis), 92AV3C.spc (axis calibration), and 92AV3GT.GIS (per-pixel land_cover_class). The semantic test validates a rows=10:12, cols=20:22 ROI against the full 21,025-record expansion and a sparse mask [(0,0), (72,36), (144,144), (10,20)] for caller-ordered selection, plus the refusal paths for empty and out-of-bounds masks. ERDAS LAN is sidecar-bearing: open_path reads the .lan plus both sidecars from disk, open_with_sidecars serves them from memory, and open_bytes returns Error::UnsupportedSidecar because the .spc axis is mandatory.