Interferometric Subsidence: 70 Wells

The erasure of hyper-dense physical architecture does not cancel its environmental extraction; memory persists as a permanent, measurable collapse in the subterranean pressure gradient.

A CNC mill carves InSAR groundwater subsidence data into granite on-site. · motion: eroding downward at the millimeter scale of geological subsidence

wall text

Demolished in 1993, the Kowloon Walled City left a persistent geological scar masked by public parkland. Decades of unregulated well extraction collapsed the subterranean pore-water pressure. This installation transposes Synthetic Aperture Radar Interferometry (InSAR) data—which measures millimeter-scale surface displacement—into an inverted digital elevation model. Operating inside the park's Lingyun Pavilion, a CNC milling machine translates these volumetric ground deficits directly into a block of raw granite. As satellite datasets record the ongoing soil compaction, the toolpath erodes the stone to physically manifest the site's enduring hydrological extraction debt.

shown: Installed outdoors directly on the footprint of the former South Gate within Kowloon Walled City Park, running continuously until the basalt block is completely perforated.

anchor facts used

The settlement occupied a strictly bounded 2.7-hectare physical footprint
Due to lack of municipal utilities, residents dug approximately 70 unregulated wells to supply water to 50,000 people
The continuous mechanical pumping of groundwater severely depleted the local aquifer
The dense architecture was completely demolished in 1993 and replaced by a surface-level Jiangnan-style park, preserving only the Qing dynasty Yamen

mechanism

Synthetic Aperture Radar Interferometry (InSAR) — Sentinel-1 satellite radar data is continuously scraped to measure millimeter-scale ground displacement specifically at coordinates 22.3322° N, 114.1903° E.
1. Satellite data acquisition and phase-shift mapping over the target coordinates.
Terzaghi's Principle of Effective Stress — The data stream filters out regional Hong Kong settling to isolate the specific void left by historic pore-water pressure loss.
2. Isolation of localized soil skeleton compaction from regional tectonic shifts.
Digital Elevation Model (DEM) Subtraction — An algorithm subtracts the 1993 surface elevation baseline from current radar phase differences, generating a real-time, inverted 3D topography of the invisible groundwater debt.
3. Calculation of volumetric differential between historic baseline and current topology.
CNC Subtractive Milling — A multi-axis CNC router translates the inverted 3D topography into toolpaths, eroding a block of dense stone at the exact micro-metric rate the ground beneath it sinks.
4. Translation of digital topological deficit into physical material removal.

lineage

Forensic Architecture, 'Ground Truth' — Adopts their rigorous use of geospatial data as forensic evidence, but redirects it from analyzing state violence to uncovering historical environmental extraction.
Hans Haacke, 'Condensation Cube' (1965) — Expands Haacke's closed-system hydrological cycle to the scale of an urban aquifer, visualizing the permanent deficit rather than the presence of water.
Ryoji Ikeda, 'data.path' — Rejects the frictionless, immaterial abstraction of Ikeda's digital space, forcing data back into heavy, subtractive physical material.

curatorial qa (machine verdict, unedited)

SCORE 4/5 after 1 attempt(s)
READS: The installation clearly connects localized InSAR subsidence data from the demolished Kowloon Walled City footprint to physical CNC carving of topographic deficits into stone on-site.
FAILS: The direct mathematical feed from satellite phase shifts to toolpath execution is not visually evident on the controller screen.

spec: antigravity agent · keyframe/artifact: gemini-3.1-flash-image · video: veo-3.1 image-to-video · qa+wall text: gemini-3.7-flash watching the render · 46.5s total