# ADR 0041: Registered map increment and rolling local occupancy

Date: 2026-08-05
Status: accepted and implemented for M4.5R/M4.6

## Context

The recorded K1 topic `lixel/application/report/lio_pcl` is post-LIO data in the
vendor SLAM map frame. In RAVNOVES00 it behaves as a registered map increment:
one message contains points contributed at that moment, not a complete scan of
everything currently visible. Therefore a structure can remain physically
present while its points are absent from a later message.

M4.5 originally applied a `0.75 s` temporal object hold directly to those
increments. M4.6 then rendered the current increment as if it were the complete
LiDAR scene. At frame `1880` the exact camera frame visibly contains two
concrete hemispheres, while the current `lio_pcl` increment has no corresponding
points in the corridor. The old result `m4-threat-replay-78a06d...` consequently
lost them from 3D. This was a representation error, not evidence that LiDAR had
measured free space.

## Decision

Mission Core keeps three distinct products:

```text
current registered increment ──> exact source context
current occupied components ───> temporal identity and motion evidence
bounded rolling occupancy ─────> conservative local obstacle presence
```

`RollingLocalObstacleMapProvider` accumulates only qualified current occupied
cells in the SLAM map frame. It never interprets missing republication as free
space. Retained cells are evicted only by explicit bounds:

- voxel size `0.45 m`;
- retention `3.0 s`;
- local radius `12.0 m` around the recorded pose;
- maximum `65,536` active cells, with fail-closed capacity handling;
- bounded component size/count and deterministic 26-neighbour connectivity.

The provider publishes only cells not present in the current increment as
`TemporalState.RETAINED`. Current and retained identities cannot overlap.
Retained components have ephemeral identity, carry their last-hit age and never
claim current motion. They may assert `threat` when their occupied cells
intersect the current virtual corridor; outside the corridor they remain
`unknown`, never `not-threat`.

The `0.75 s` temporal object state remains separate. It continues to answer
whether a current component has enough bounded history for motion reasoning. It
is not a map-clearing policy.

## Evidence and acceptance

The accepted M4.5R result is
`m4-temporal-replay-b8611526dfcd2b9be9049560d751bbd23a9ad54b7dda8e9dc48a17374d46266e`.
Its frame ledger SHA-256 is
`08a03669d3487ecf7bd62b047ae5b8d1ff586a27e7435e5f235907a4d709dd25`.
Across all `4,489` source frames it records:

- `848,868` current increment occupied cells;
- `69,855` retained component publications and `1,776,145` retained cell
  publications;
- peak `907` active cells and `35` retained components;
- `29,620` time evictions, `6,512` radius evictions and zero capacity drops;
- maximum retained age exactly `3.0 s` and `587` active cells at replay end.

The accepted M4.6 result is
`m4-threat-replay-ef521b23eee704dee99856b6e93d5047a9b358e21ffda3ea9cacc2ef768164d9`.
All `4,489` frames completed with `27,299` current metric, `69,855` rolling-map,
`37,995` stale/held and `10,158` camera-only evidence publications assessed
exactly once. Decisions are `6,626 threat`, `10,700 not-threat` and `127,981
unknown`. All `10/10` deterministic fixtures pass with zero critical false-safe
outcomes.

Frame `1880` is a mandatory engineering visual regression. It binds two
separate body-frame regions to two retained components. The near region must
assert threat; both regions are present in the accepted result. These anchors
encode a reproducible owner-reviewed visual case, not independent object truth.

The common LAB viewer exposes `CURRENT INCREMENT` and `ROLLING MAP` as separate
layers over the same selected frame. The current point count is not relabelled
as a complete scan, and retained occupied cells remain independently hideable.

## Consequences and limitations

- Missing points cannot create free-space or navigation authority.
- Short-lived obstacle disappearance caused solely by incremental publication
  is removed from the replay decision path.
- A moving object may leave a conservative ghost for up to `3.0 s`; retained
  occupancy can block but cannot claim motion or clearance.
- No ray-level free-space clearing is available in this recording. A future raw
  scan/ray provider must add explicit observation and clearing semantics rather
  than weakening this contract.
- The two frame-1880 anchors are regression evidence, not independent truth,
  detector accuracy or physical collision acceptance.
- Live K1, measured `T_body_from_sensor`, physical body geometry, navigation,
  commands and actuation remain outside M4.5R/M4.6 authority.