feat(geo): adopt Mapbox building calibration (3.1 m per level) (#26)

Merged PR #26: adopt Mapbox building calibration

Co-authored-by: Zwitschi <zwitschi82@gmail.com>

Art/blender/README.md

@@ -80,10 +80,7 @@ LD_LIBRARY_PATH="$B/blender/lib" "$B/blender/blender" -b --factory-startup \
 ```
 
 - `Road_Hollywood`: 8 120 verts, 7 812 faces, carriageway −10.5…+10.5 m, DEM elevations plus a 2 cm lift so it does not z-fight the terrain.
-- `Sidewalk_South` 4.0 m wide, `Sidewalk_North` 5.3 m wide. The kerb upstand is
-  **full at the road-side edge and tapers to zero at the building-side edge**, so
-  the walk surface meets the terrain flush (before `0.1.1` the outer lip stood the
-  full kerb height above the DEM — a 15.8 cm ledge).
+- `Sidewalk_South` 4.0 m wide, `Sidewalk_North` 5.3 m wide. The kerb upstand is **full at the road-side edge and tapers to zero at the building-side edge**, so the walk surface meets the terrain flush (before `0.1.1` the outer lip stood the full kerb height above the DEM — a 15.8 cm ledge).
 - `Kerb_South`, `Kerb_North`: vertical faces, mostly **0.13 m** — the 0.15 m assumption minus nothing on the road side — and flushed to 0 within ±2.5 m of each signalised crossing with a 1.5 m blend. Measured from the built mesh: 256 steps at 0.13 m, 15 flush, a few in transition.
 
 Crown check on the built mesh at mid-block: gutter −10.5 m → +0.99, −5 m → +1.38, centre → +1.52, +5 m → +1.58, +10.5 m → +1.52. The crown sits just north of the centreline, as the cross-sections said.
@@ -106,32 +103,20 @@ Objects are appended from the source files, not regenerated, and grouped into `S
 
 A downward raycast on a 1 m grid along both sidewalks and the designated crossing, ignoring blockout meshes so marquees and canopies overhead do not count as ground:
 
-| Route             | Samples | Holes | Z range       | Worst step |
-| ----------------- | ------: | ----: | ------------- | ---------: |
-| South sidewalk    |     279 |     0 | −0.48 … +3.06 |    13.4 cm (s=198) |
+| Route             | Samples | Holes | Z range       |        Worst step |
+| ----------------- | ------: | ----: | ------------- | ----------------: |
+| South sidewalk    |     279 |     0 | −0.48 … +3.06 |   13.4 cm (s=198) |
 | North sidewalk    |     279 |     0 | +0.06 … +3.76 |     6.9 cm (s=33) |
-| Crossing at 130 m |      26 |     0 | +1.14 … +1.80 |     9.0 cm (off −8.5) |
+| Crossing at 130 m |      26 |     0 | +1.14 … +1.80 | 9.0 cm (off −8.5) |
 
-At `--sample 0.25` the same routes measure 11.6 cm / 8.0 cm / 3.4 cm. The
-pre-check now prints the grade and the **location** of the worst step, and its
-coverage no longer shrinks with `--sample`.
+At `--sample 0.25` the same routes measure 11.6 cm / 8.0 cm / 3.4 cm. The pre-check now prints the grade and the **location** of the worst step, and its coverage no longer shrinks with `--sample`.
 
 No holes anywhere, so nothing drops the player on either side. The two flagged steps:
 
-- ~~15.8 cm at s≈207, the sidewalk's outer edge~~ — **fixed in `0.1.1`**: the
-  sidewalk upstand now tapers to zero at the building side, so the outer edge is
-  flush with the terrain (north route 15.1 → 6.9 cm).
-- ~~10–13 cm steps at the crossings, ~10 % ramp over 1.5 m~~ — **fixed in `0.1.1`**:
-  the ramp run is now derived from a target grade (`--max-ramp-grade`, default 8 %),
-  giving 1.63 m instead of the fixed 1.5 m (8.7 %). Measured at 0.25 m sampling the
-  crossing now steps 3.4 cm (~1.4 % of the route) at the kerb line.
+- ~~15.8 cm at s≈207, the sidewalk's outer edge~~ — **fixed in `0.1.1`**: the sidewalk upstand now tapers to zero at the building side, so the outer edge is flush with the terrain (north route 15.1 → 6.9 cm).
+- ~~10–13 cm steps at the crossings, ~10 % ramp over 1.5 m~~ — **fixed in `0.1.1`**: the ramp run is now derived from a target grade (`--max-ramp-grade`, default 8 %), giving 1.63 m instead of the fixed 1.5 m (8.7 %). Measured at 0.25 m sampling the crossing now steps 3.4 cm (~1.4 % of the route) at the kerb line.
 
-**Remaining finding (not a crossing, not the outer edge):** the south route still
-measures a **13.4 cm step at s≈198 m** (11.6 cm at 0.25 m sampling) and the north
-route 8.0 cm at s≈251 m. Neither is at a crossing and neither is the outer lip, so
-this is a local discontinuity in the sidewalk strip — most likely the DEM sampling
-or a centreline vertex near the block ends. Tracked under the `0.1.1` "audit any
-collision gaps" item rather than left undocumented.
+**Remaining finding (not a crossing, not the outer edge):** the south route still measures a **13.4 cm step at s≈198 m** (11.6 cm at 0.25 m sampling) and the north route 8.0 cm at s≈251 m. Neither is at a crossing and neither is the outer lip, so this is a local discontinuity in the sidewalk strip — most likely the DEM sampling or a centreline vertex near the block ends. Tracked under the `0.1.1` "audit any collision gaps" item rather than left undocumented.
 
 This is a pre-check, not the `0.1.0` release check: the release check is traversal in the engine.
 
@@ -146,13 +131,15 @@ Blender works in metres, and the imported meshes match the OSM geometry, so the
 | Building | Blender dimensions | OSM way outline | Height source |
 | --- | --- | --- | --- |
 | El Capitan Entertainment Centre | 25.72 × 54.47 × 14.50 m | 25.75 × 54.88 m | `height` tag 14.5 |
-| El Capitan Theatre | 38.66 × 54.46 × 20.96 m | 38.59 × 54.87 m | `building:levels=6` × 3.2 m, plus roof |
+| El Capitan Theatre | 38.66 × 54.46 × 20.55 m | 38.59 × 54.87 m | `building:levels=6` × **3.1 m**, plus ~1.9 m roof |
 | Madame Tussaud's | 42.48 × 56.77 × 15.90 m | 42.0 m frontage | `height` tag 15.9 |
 | TCL Chinese Theatre | 43.78 × 75.90 × 18.10 m | 44.0 m frontage | `height` tag 18.1 |
 
 Widths agree to a few centimetres; depths differ by up to 0.4 m because Blosm assembles **multipolygon relations**, not the raw way I measured. Placement after the frame correction agrees with the UTM control points to 0.1–0.5 m per building — the residual is relation assembly and Blosm's edge straightening, not projection.
 
-Buildings **without** a `height` tag get levels × 3.2 m, which is a placeholder, not evidence. Every such height is a modelling decision to be replaced from the reference photography.
+Buildings **without** a `height` tag get levels × **3.1 m**. The storey height was 3.2 m until 2026-11-09, when a cross-check of every block building against Mapbox's building data (`Geo/tools/mapbox_buildings.py`) showed our figure running 0.6 m high per six levels — i.e. 3.1 m per level — and that calibration was adopted. The few buildings where Mapbox disagreed with a pure `levels × 3.1 m` fallback carry an explicit override in `Geo/tools/block_height_report.py::HEIGHT_OVERRIDES`.
+
+Blosm adds roof mass on top of `levels × levelHeight`: the two `levels`-derived frontage buildings both land ~1.9 m above their table height (6922 39.1 m against 37.2 m, El Capitan Theatre 20.5 m against 18.6 m). That offset is the roof, not a height error — the table records the tagged height, the mesh records the storey plus its roof.
 
 ## Relation completeness
 

Art/blender/blockout/blosm_blockout.py

@@ -40,7 +40,9 @@ def parse_args():
     ap.add_argument("--osm", required=True, help="local .osm file to import")
     ap.add_argument("--bounds", required=True, help="south,west,north,east in WGS84 degrees")
     ap.add_argument("--out", required=True, help="output .blend path")
-    ap.add_argument("--level-height", type=float, default=3.2, help="metres per building level")
+    # 3.1 m, not 3.2: calibrated against Mapbox building data on 2026-11-09
+    # (see Geo/tools/mapbox_buildings.py and Geo/tools/block_height_report.py).
+    ap.add_argument("--level-height", type=float, default=3.1, help="metres per building level")
     ap.add_argument("--origin", default=None,
                     help="lat,lon to use as the Blender origin (project origin). Default: Blosm centres on the extract")
     ap.add_argument("--no-subdivide", action="store_true", help="skip OSM area subdivision")