Route `/dashboard/sites/[id]/map3`; code in `src/components/site-map-v3` (a copy of Map 2's 3D map plus the Ground layers), `src/lib/site-map-v3` (pure logic). Map 1 and Map 2 are unchanged. Same orbit/pan/zoom, layers, section click and double-click progress popup as Map 2; progress ticks use the same local scenario as Map 2.
## Layers
Map 2's own layers, plus three Map 3 layers in the Ground tab: ground heat map (hillshaded), ground contours, cut & fill. The text below is the full list.
Roads & kerbs, road markings, stormwater, sewer and water routes, ground heat map (+ hillshade; off by default), ground contours (0.1 m, major 0.5 m, generated from the ground grid), finished-level heat map, cut & fill, centreline with 20 m chainage, services (plan routes), progress. Layers with no data are disabled with a reason. When progress arrives or changes, the progress layer switches on and a message says so.
## Cut & fill
For each 1 m cell inside a road area where both ground and design exist: `diff = ground - (finished level - build-up depth)`; positive = cut. Depth comes from the drawn build layers (internal paving 0.55 m); builds under 0.1 m (asphalt wearing course only, walkways) use the adjustable fallback (default 0.45 m). Cells without ground get no value (hatched grey). Ground source can be Chris's contours or the consultant's drawn cross-sections.
## Limits
- Ground survey covers Cedar Gate Road only; other roads are not calculated.
- Chris's contours sit ~0.13 m below the drawn-section ground (mean abs 0.16 m, max 0.68 m); survey date and datum unconfirmed.
- Progress is read-only here; Map 2 scenario edits stay in that browser.
## Extension points
- Aerial imagery: add a raster layer to `render.ts` once the site is georeferenced (no tile requests today).
- Nellmapius: needs terrain extracted from the "Detail Contour Plan" PDF first.
Strips every other map layer and tints each road section by how many of the ticked pavement layers are done (red none, amber some, green all), with a "done/shown" label. The side list gives each section's layer checklist; "Tick layers" or a double-click on the map opens the section's tick-off popup. Logic in `src/lib/site-map-v3/layer-progress.ts`.
