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VLM v0.1 validation report

  • Release: opera_vlm v0.1.0 (VLM-S1), Venti plan T57
  • Status: draft, 2026-10-16
  • Inputs: DISP-S1 + DISP-CAL (cal-disp v0.5) on asc/desc frame pairs
  • Validator: disp2vlm-validate vlm, independent GNSS (UNR daily stations, MIDAS), never the calibration grid

Gate (decision 0003)

Per-station vertical rates (VLM minus GNSS up) on stations seen by both looks (mode 1), outside deforming areas and event footprints. Pass: |median| ≤ 1 mm/yr and NMAD ≤ 2 mm/yr, on at least 20 stations. RMSE is reported, not gated.

Results

Frames DISP-CAL gated n median NMAD RMSE (mm/yr) verdict
LA F16940 + F18904 (2016–2023) v0.5, T46 runs 172 −0.42 1.44 2.67 PASS
Houston F08882 + F38238 v0.5, T46 runs 18 +0.23 2.03 4.17 not assessable (< 20)
Houston F08882 + F38238 v0.5.0 release (confirmation run) 19 −0.03 2.39 3.52 not assessable (< 20)
  • LA meets the owner's 1–2 mm/yr target: 80% of stations are within 2 mm/yr. Six local sites (BRAN, CRHS, TRAK, WNRA, MILK, GISA) dominate the RMSE; without them it is 1.56.
  • Houston is an edge case. Most of its stations are inside the Houston-Galveston subsidence area, so 19 remain for the gate. On the release calibration the median moves to zero and RMSE improves (the worst stations improve by 2–3 mm/yr), but NMAD rises to 2.39.
  • New York and Montana are limited by data: New York's descending DISP has a 2020–2022 gap, and Montana has no winter DISP and two stations. Oklahoma City has no descending DISP-S1.

σ realism (reported)

Coverage of |z| < 1.96 and the robust spread of z, by span:

span (yr) LA coverage / NMAD(z) Houston (release) coverage / NMAD(z)
0 0.76 / 0.82 0.97 / 0.84
1 0.89 / 0.82 0.93 / 0.87
2 0.85 / 0.87 0.87 / 1.04
3 0.77 / 1.16 0.79 / 1.19
5 0.81 / 1.14 0.82 / 1.49
7 0.68 / 1.45 0.71 / 1.47
  • The per-look sigma_rate term (1.5 mm/yr) keeps the spread near 1 up to about 2 years.
  • Beyond 3 years σ under-covers (coverage 70–80%, NMAD(z) 1.1–1.5): the error grows faster than linearly with the span. Open for v0.2.

Open items

  • Re-run LA on the v0.5.0 release calibration. LA's frame table now has stratified tropo and island regions; the LA numbers above use the T46 calibration.
  • Long-span σ realism (above).
  • Houston in the final edge-case pass.
  • VLM v0.2: the tiled SAS (Venti plan T63) uses every overlapping asc/desc track per MGRS tile, which should help frames like Houston and New York.