The earthwork and the ground
The enclosure ditch and bank — Established
Source: Cleal, Walker & Montague, Stonehenge in its Landscape:
Twentieth-century excavations (English Heritage Archaeological Report 10,
1995) — the definitive excavation synthesis.
- The earliest monument (c. 2900 BC) is the circular earthwork enclosure:
a ditch with an internal bank and a low external counterscarp bank.
The main bank inside the ditch is the reverse of the classic henge
arrangement — by the strict typology, Stonehenge is not a henge.
- Circuit roughly 110 m across; ditch about 5–6 m wide, dug
1.4–2.1 m into the chalk in irregular segments (it reads as a chain
of conjoined pits); the fresh bank stood perhaps 2 m of bright
chalk rubble, about 6 m wide.
- Today both survive as gentle grassed swellings of roughly half a
metre — silt in the ditch, slump on the bank.
- Two causeways break the circuit: the main north-east entrance on
the monument’s axis, where the Avenue meets the enclosure, and a
smaller southern gap.
- Antler picks from the ditch bottom furnished the radiocarbon dates;
the diggers backfilled placed deposits (cattle bone already old when
buried) — the enclosure was never merely a quarry for the bank.
In the app: HengeGeometry/Earthwork.swift models the circuit as an
analytic profile (state-aware: as-dug against today’s swell), tested in
EarthworkTests — causeway level on the axis, bank inside ditch, as-dug
dwarfing as-stands.
The ground surface — Established observation, Speculative palette
Reference imagery: aerial photograph of the monument from the north-west
(supplied by the owner, 2026-07-31, from Nature’s news coverage of the
Altar Stone work). What it shows, and what the renderer takes from it:
- Chalk downland is not one green: a patchwork metres across — thin
worn turf reading pale where the chalk comes through, ranker growth,
wear scars. The renderer’s two-band mottle is calibrated to this.
- The earthwork ring reads paler than the field — thin sward over
chalky bank material. The wear channel on the ring carries this.
- The enclosure interior reads differently from the surrounding pasture
(mown versus grazed in the photograph — a modern management artefact,
not reconstructed).
- Every colour triple in the renderer is an artistic reading —
Speculative by construction; no source publishes reflectance spectra
for this turf.
The wider landscape — Established
- Terrain: Environment Agency LiDAR (1 m, bare earth) heightfield, baked to a 768×768
grid at 40 m spacing (±15.3 km) by
scripts/bake_terrain.py — the
skyline the sun actually rises over.
- Barrows and field boundaries visible in the reference photograph are
not yet modelled.