EMSA/MAS MSA (ISO 22029)

Status: Supported (scoped) · Vendor: EMSA / MAS / ISO · Extensions: .msa

EMSA/MAS .msa is the single-spectrum ASCII interchange format from the Microscopy Society of America / European Microbeam Analysis Society, standardised as ISO 22029. It is used mainly for EDS/EELS microanalysis spectra, where the X axis is typically energy in eV. nirs4all-formats reads it as an adjacent, narrow text format so these files can be probed and disambiguated.

Instruments & software

Written by electron-microscopy and microanalysis software (EDS / EELS / WDS acquisition packages) following the EMSA/MAS specification and ISO 22029:2022. Committed fixtures include ISO 22029:2022 compliance examples and the classic EMSA example1/example2 spectra.

File structure

Plain ASCII with two parts:

  • Header — label/value records each beginning with a single #, e.g. #FORMAT, #TITLE, #NPOINTS, #XUNITS, #YUNITS, #XPERCHAN, #OFFSET, #CHOFFSET, #DATATYPE. Repeated keys (including multi-line #TITLE and #COMMENT) are kept. The data section begins after #SPECTRUM and ends at #ENDOFDATA.

  • Data — either #DATATYPE: XY explicit X/Y pairs, or #DATATYPE: Y ordinate-only arrays. Numeric payloads may be comma-, semicolon-, tab- or whitespace-separated, including scientific notation.

The reader sniffs files with an .msa extension or an EMSA/MAS marker that also contain #FORMAT.

What nirs4all-formats extracts

  • Signal — one SpectralRecord with a single signal named from #YLABEL (default signal). Signal type is inferred from the Y label/units; an intensity label with no recognised optical type maps to RawCounts, otherwise Unknown.

  • Axis — for XY data the X column is the axis; for Y data the axis is reconstructed as OFFSET + (index + CHOFFSET) * XPERCHAN. The kind/unit follow #XUNITS: energy eV, wavenumber cm-1, wavelength nm, else index.

  • Metadata — the full header (with repeated keys preserved) is stored under metadata.emsa_mas.

  • Provenance & warnings — source file + SHA-256, reader name/version; a #NPOINTS consistency check truncates extra values with a provenance warning.

Variants & support status

Variant

Status

Notes

#DATATYPE: XY (incl. NCOLUMNS 2)

Supported

Explicit energy/value pairs.

#DATATYPE: Y ordinate-only

Supported

Axis from OFFSET/XPERCHAN/CHOFFSET.

Scientific-notation payloads

Supported

Parsed in either data type.

Multi-line #TITLE / #COMMENT

Supported

Repeated header keys preserved.

Invalid date/time, empty fields

Supported (preserved)

Kept verbatim for reference comparison; not yet validated.

Limitations & known gaps

  • Date/time and other ISO 22029 metadata fields are not yet validated; invalid metadata is preserved rather than flagged. Stricter validation would be emitted as warnings, not hard failures.

  • EDS/EELS signal families are currently typed as RawCounts/Unknown; whether they deserve dedicated SignalType variants is undecided.

  • Only single-spectrum .msa files are handled (the format itself is single-spectrum).

Reference readers

rsciio.msa from the HyperSpy / RosettaSciIO stack is the reference loader. Full-array conformance reports against it are still to be added.

Samples & validation

Fixtures live under samples/ and are covered by golden summaries in crates/nirs4all-formats/tests/goldens/; the probe reports format emsa-mas-msa at Confidence::Definite. Committed control values:

File

Data type

Points

Axis

Value control

ISO_22029_2022_compliance.msa

XY

21

energy 520.13 → 580.50 eV

4066 → 4217

ISO_22029_2022_compliance_XY_NCOLUMNS2.msa

XY

21

energy 520.13 → 580.50 eV

4066 → 4217

ISO_22029_2022_compliance_scientific_notation.msa

XY

21

scientific notation

golden summary

ISO_22029_2022_compliance_title_multiple_line.msa

XY

21

multi-line title metadata

golden summary

example1.msa, example1_with_seconds.msa, example2.msa

examples

variable

metadata/date variants

golden summaries

example1_wrong_date.msa, example1_wrong_date_empty_field.msa

XY

20

invalid date/empty fields preserved; extra payload row truncated with warning

golden summaries

example2_NCOLUMNS5.msa

Y

80

energy 0.0 → 790.0 eV

65.820 → 49.442

minimum_metadata.msa

minimal

1

0.0 index

1.0