ASD FieldSpec

Status: Supported (scoped) · Vendor: ASD / Malvern Panalytical · Extensions: .asd (also extension-less numeric files such as .000)

ASD FieldSpec is the native binary format of ASD (now Malvern Panalytical) portable field spectrometers — FieldSpec, LabSpec and HandHeld instruments used for reflectance, radiance and raw-counts measurements across the VNIR/SWIR range. A single .asd file is a fixed header followed by the primary spectrum and, in newer revisions, several embedded internal blocks (reference, classifier, dependent variables, calibration, audit log, signature). nirs4all-formats decodes the primary spectrum of revisions 1, 6, 7 and 8 and inventories the remaining blocks.

Instruments & software

Written by ASD’s RS³ / ViewSpec / Indico software for FieldSpec full-range, FieldSpec Pro, LabSpec and HandHeld spectrometers. The instrument model is read from the header and mapped to labels such as fieldspec_full_range, labspec_pro or handheld.

File structure

  • File-version magic — the first three bytes carry an ASCII revision prefix: ASD (revision 1), then as2…as8. The format is detected by magic, so files without an .asd extension (e.g. .000) are still recognised.

  • Fixed header (484 bytes) — comments, acquisition time, program/file version, dark/reference timestamps, data type, data format, first wavelength (channel1), wavelength step, channel count, integration time, foreoptic, detector gains/offsets, splice wavelengths, instrument and calibration identifiers, and sample/reference/dark counts.

  • Primary spectrum — channels values in float32 (data format 0), int32 (1) or float64 (2), immediately after the header.

  • Internal blocks (revision-gated) — reference header + spectrum (rev ≥ 2), classifier data and dependent variables (rev ≥ 6), calibration header + spectra (rev ≥ 7), audit log and signature (rev 8), followed by an optional ff fe fd footer marker and zero padding.

What nirs4all-formats extracts

  • Signals — one SpectralRecord carrying the primary spectrum as a single signal, named and typed from the header data_type: reflectance, radiance, irradiance, transmittance, absolute_reflectance or raw.

  • Axis — a wavelength axis in nm, generated from channel1 + wavelength_step × index.

  • Metadata — the full decoded fixed header under metadata.asd (acquisition time, versions, integration time, gains/offsets, splice wavelengths, display range, instrument/calibration labels, smart-detector type). An inventory of internal blocks is exposed under metadata.asd.secondary_blocks, with byte accounting in trailing_block_bytes, decoded_trailing_block_bytes and undecoded_trailing_block_bytes.

  • Provenance & warnings — asd_secondary_spectra_not_emitted is raised when reference/calibration spectra are present but not emitted as records; trailing_asd_blocks_not_decoded is raised when bytes remain outside the known block inventory.

Variants & support status

Variant

Status

Notes

Revision 1 (ASD) primary spectrum

Supported

float32 legacy .000 covered.

Revisions 6 / 7 / 8 primary spectrum

Supported

float64 reflectance, radiance and raw-counts fixtures covered.

int32 / float64 payload encodings

Supported

Selected by the header data_format field.

Embedded reference / calibration / classifier / dependent-variable blocks

Detected / refused

Inventoried with byte offsets and counts, but not decoded into additional signals or targets.

v8 audit log / digital signature blocks

Detected / refused

Summarised for diagnostics only.

Revisions 3 / 4 / 5

Blocked

Recognised by magic but no open fixture to validate.

Separate .ILL / .REF / .RAW calibration companions

Blocked

No redistributable sample set yet (matrix: non viable).

Limitations & known gaps

  • Embedded secondary spectra (reference, calibration) are counted and typed but their numeric payloads are not exposed as signals.

  • Classifier and dependent-variable blocks are summarised for diagnostics, not promoted to calibrated quantitative targets.

  • Revisions 3–5 and files exercising the full internal-block set still need open samples; the companion .ILL/.REF/.RAW calibration files have no redistributable fixture.

Reference readers

pyASDReader (revision 6/7/8 metadata and spectrum checks) and prospectr::readASD() (legacy .000 coverage). asdreader, specdal and spectrolab remain reference candidates for deeper conformance once the R reference path is automated.

Samples & validation

Six fixtures under samples/asd/ are golden-backed in crates/nirs4all-formats/tests/goldens/ with direct semantic tests: 3L9257.000 (rev 1, float32, reflectance), v6sample00000.asd (rev 6, raw counts), v7_field_44231B009.asd (rev 7, reflectance), v7sample00000.asd (rev 7, radiance), soil.asd and v8sample00001.asd (rev 8, raw counts). The probe reports format asd-fieldspec at Confidence::Definite.