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Eulumdat Photometric Data.

At a glance
Original creator Axel Stockmar, Light Consult Inc.
First published 1990
Purpose EULUMDAT, the European format for a luminaire's measured light distribution, with every value at a fixed line position.
Extensions .ldt
Poka parser poka-ldt
Viewer poka-metadata-card-viewer
Depth tier Metadata card (see Depth tiers)
Breadth tier B3 Core (see Breadth tiers)

How much Poka reads

B3 Core. Only the main content type or types are decoded (for example geometry but not materials, layers or annotations, or only one version family). The list of gaps is substantial.

Confidence: medium (the reviewer read the code). Basis: Reviewed 2026-10-16: poka-ldt lib.rs (parse_ldt, symmetry handling, build_ast, 10 unit tests) and tests/samples.rs over 2 corpus files (both symmetry families, derived line count checked against real files). The intensity table is read, and C and G angles are parsed, but the card shows only header facts, lamp sets, peak and flux. B4 would also be defensible.

What Poka does not read

  • Intensity table is not displayed: no polar curve, no per-angle values; C-angle and gamma-angle lists are parsed but not shown
  • Direct ratios (ten room indices) are parsed but not shown
  • Luminous-area heights at C0, C90, C180 and C270 (lines 18 to 21) are not read
  • Conversion factor is parsed but not shown (flux and peak are not visibly scaled by it)
  • No derived photometric values such as beam angle or zonal lumens
  • Only two corpus files

Background

Wikipedia says Axel Stockmar of Light Consult Inc., Berlin, proposed the format in 1990 and calls it the European equivalent of the IES format. Nothing in the file names its fields: line 23 is the light output ratio because it is line 23. Poka reads the positional header (type, symmetry, number and spacing of C-planes and angles, lamps, ratios) and the intensity table, and shows the header facts, lamp sets, peak and flux on a metadata card; the intensity table is read but not displayed.

Versions

Version Identifier Poka Note
EULUMDAT Read

Libraries

Libraries Poka uses or has assessed for this format, with the status, licence and language the registry records.

  • lidrs (candidate; MIT; Rust; https://github.com/sammorrell/lidrs) — Reads and writes EULUMDAT .ldt/.eul and IES LM-63; only Type C photometry is converted. lib.rs lists a custom licence.
  • eulumdat-rs (reference; AGPL-3.0-or-later; Rust; https://github.com/holg/eulumdat-rs) — copyleft; Workspace that parses, writes and analyses LDT, IES and ATLA/TM-33; has WASM and Python bindings. Strong copyleft.
  • eulumdat (reference; AGPL-3.0-or-later; Rust; https://github.com/holg/eulumdat-rs) — copyleft; Eulumdat (LDT) and IES photometric file parser, writer, and validator for Rust; v0.7.1, updated 2026-09-18; matched on lib.rs, not tested
  • eulumdat-egui (reference; AGPL-3.0-or-later; Rust; https://github.com/holg/eulumdat-rs) — copyleft; Cross-platform GUI application for viewing EULUMDAT/LDT and IES photometric files; v0.7.0, updated 2026-05-18; matched on lib.rs, not tested

Sources