# URMA ceiling and visibility source comparisons

Independent ecCodes decoding and the pinned Icechunk snapshot return identical full grids for these six messages (maximum absolute difference 0 m). All 3,744,965 cells are finite; none of these messages declares a bitmap. This establishes preserved values, not their meteorological interpretation or historical deployment cause.

| UTC valid time | Field | Source range (m) | Cells equal to 1 m | Source |
|---|---|---|---:|---|
| 2018-12-03T11:00:00+00:00 | cloud_ceiling_height | 0.1–20000.0 | 503 | [GRIB](https://noaa-urma-pds.s3.amazonaws.com/urma2p5.20181203/urma2p5.t11z.2dvaranl_ndfd.grb2_wexp) |
| 2018-12-03T11:00:00+00:00 | visibility_surface | 0.0–20000.0 | 3 | [GRIB](https://noaa-urma-pds.s3.amazonaws.com/urma2p5.20181203/urma2p5.t11z.2dvaranl_ndfd.grb2_wexp) |
| 2018-12-03T12:00:00+00:00 | cloud_ceiling_height | 1.0–16000.0 | 52599 | [GRIB](https://noaa-urma-pds.s3.amazonaws.com/urma2p5.20181203/urma2p5.t12z.2dvaranl_ndfd.grb2_wexp) |
| 2018-12-03T12:00:00+00:00 | visibility_surface | 1.0–16000.0 | 750 | [GRIB](https://noaa-urma-pds.s3.amazonaws.com/urma2p5.20181203/urma2p5.t12z.2dvaranl_ndfd.grb2_wexp) |
| 2026-10-19T12:00:00+00:00 | cloud_ceiling_height | 1.0–16000.0 | 2861 | [GRIB](https://noaa-urma-pds.s3.amazonaws.com/urma2p5.20261019/urma2p5.t12z.2dvaranl_ndfd.grb2_wexp) |
| 2026-10-19T12:00:00+00:00 | visibility_surface | 1.0–16000.0 | 291 | [GRIB](https://noaa-urma-pds.s3.amazonaws.com/urma2p5.20261019/urma2p5.t12z.2dvaranl_ndfd.grb2_wexp) |

The source message offsets, lengths and SHA-256 hashes are in [machine-readable evidence](source-bound-evidence.json). Snapshot: `8H2JJXCAF6YSMT6W121G`.