Research Date: 2026-07-16 • Beyond LiDAR — what else can detect sinkholes before they happen?
GPR vehicle-mounted is the #1 technology to add after LiDAR. Combined LiDAR (surface) + GPR (subsurface) on a single vehicle gives SinkAlert a complete road health profile — no competitor does this. InSAR (free via Sentinel-1) provides wide-area early warning. DAS fiber optic is a zero-capex partnership play with Thai telecom.
| Technology | Purchase Cost | Per-km Cost | Detect What | Fit | Verdict |
|---|---|---|---|---|---|
| GPR (Vehicle) | $14K–$35K | ฿3–8/km (own) | Subsurface voids, cavities, pipe leaks | ⭐⭐⭐⭐⭐ | BUY |
| InSAR (Sentinel-1) | FREE | FREE | Regional mm-scale subsidence | ⭐⭐⭐⭐⭐ | ALREADY PLANNED |
| DAS Fiber Optic | $0 hardware | Negotiate w/ telecom | Ground strain, vibrations, micro-events | ⭐⭐⭐⭐ | PARTNER |
| ERT (Resistivity) | ~$15K–$30K | ฿500–2,000/site | Void confirmation, water pathways | ⭐⭐⭐ | CONFIRMATION ONLY |
| UAV Thermal IR | ฿80K–150K | ฿2–5/km | Surface moisture anomalies | ⭐⭐⭐ | NICE-TO-HAVE |
| Microgravity | $50K+ | Very slow | Deep density anomalies | ⭐ | SKIP |
| Layer | LiDAR | GPR |
|---|---|---|
| Surface | ✅ Road cracks, subsidence, potholes | — |
| Shallow (0–2m) | — | ✅ Pipe leaks, washout, erosion |
| Medium (2–10m) | — | ✅ Voids, cavities, karst features |
| Deep (10m+) | — | Partial (lower freq needed) |
The killer combination: Mount both on the same vehicle. Drive once. Get surface (LiDAR point cloud) AND subsurface (GPR radargram) simultaneously. Feed both into XGBoost. No competitor combines these.
| Option | Price |
|---|---|
| Entry-level (single-channel cart) | $14,000 |
| Mid-range (vehicle-mountable) | $25,000–$35,000 |
| High-end (multi-channel array) | $65,000–$100,000+ |
| Rental (monthly) | $400–$1,750 |
| Contractor daily rate | $1,000–$5,000/day |
DIY per-km cost: ~฿3–8/km • Vendor per-km (Thai market): ~฿500–2,000/km
Buy a mid-range vehicle-mounted GPR ($25K–$35K) and mount on the same vehicle as LiDAR. Combined LiDAR + GPR vehicle: ฿118K (LiDAR) + ~฿900K (GPR) = ~฿1,020,000 total. Payback in ~500 km vs contractor rates.
Sentinel-1 data is free from ESA Copernicus. Revisit every 6–12 days over Bangkok. Already SinkAlert Level 1 (wide-area screening).
| Paper | Year | Key Finding |
|---|---|---|
| Land subsidence in Bangkok… InSAR + ML | 2024 | Random Forest + InSAR predicts Bangkok subsidence 2023–2048. Science of the Total Environment |
| Mae Moh mine InSAR | CHULA | Sentinel-1 SBAS-InSAR applied to Thai geological monitoring |
| Anantrasirichai et al. | 2020 | CNN-based deformation detection from sparse InSAR. 105 citations. IEEE TGRS |
Register for Copernicus Data Space Ecosystem (free). Download Sentinel-1 SLC over Bangkok. Apply SBAS/PS-InSAR processing. Use as early warning layer — flag high-subsidence zones for targeted LiDAR + GPR inspection.
Bangkok has extensive fiber optic networks (True, AIS, NT, 3BB). No new cables needed. A DAS interrogator unit ($20K–$50K) connects to existing dark fiber and monitors up to 50 km with meter-scale resolution — 24/7 continuous.
| Item | Cost |
|---|---|
| DAS interrogator unit | $20K–$50K (one-time) |
| Fiber access | Negotiable (True, AIS, NT) |
| Per-km operating cost | ~$0 (after setup) |
| Coverage | 50 km per interrogator |
Pilot partnership with a Thai telecom provider. SinkAlert provides DAS interrogator; telecom provides dark fiber along 10–20 km of high-risk Bangkok roads. Joint research paper with CHULA. DEPA would love "public-private-academic partnership" narrative.
NOT for continuous road scanning. Use as a confirmation tool: when InSAR flags a subsidence hotspot AND GPR detects a possible void, deploy ERT at that specific site to confirm the void's size, depth, and shape before excavation.
| Item | Cost |
|---|---|
| Multi-electrode ERT system | ~$15K–$30K |
| Per-site survey | 30–45 min per line |
| 10-borehole verification (ref.) | ~$18,000 |
Recommendation: Buy only after InSAR + GPR pipeline is operational.
Detects surface temperature anomalies (wet ground = cooler, dry cracks = hotter), moisture seepage, and vegetation stress above sinkholes.
| Option | Price |
|---|---|
| DJI Mavic 3 Thermal | ~฿150,000 |
| DJI Matrice 30T (enterprise) | ~฿300,000 |
Recommendation: Lower priority than GPR. Useful for rapid post-rain inspection and verifying InSAR anomalies visually.
Too slow for road-scale scanning — requires 5–15 min stationary measurements at each point. Useful for large karst basins, not Bangkok road networks. Equipment: $50K+.
| Tier | Technology | Coverage | Frequency | Cost | Status |
|---|---|---|---|---|---|
| Level 1 — Watch | Sentinel-1 InSAR | Entire Bangkok metro | Every 6–12 days | FREE | 🟡 Pending registration |
| Level 2 — Scan | Vehicle LiDAR + GPR | Target roads | Weekly–monthly | ฿7–20/km | 🟢 LiDAR researched; GPR recommended |
| Level 3 — Confirm | ERT spot surveys | Flagged sites | As needed | ฿500–2,000/site | 🟡 Future phase |
| Level 4 — Listen | DAS fiber optic | 50 km fiber | 24/7 continuous | $0/km after setup | 🔵 Partnership opportunity |
| # | Technology | Setup Cost | Annual Ops | ROI Timeline | Decision |
|---|---|---|---|---|---|
| 1 | InSAR (Sentinel-1) | $0 | $0 | Immediate | DO IT NOW |
| 2 | GPR (vehicle-mounted) | $25K–$35K | ฿50K–100K | 6–12 months | STRONG BUY |
| 3 | DAS (fiber optic) | $20K–$50K | Negotiate | 12–18 months | PURSUE |
| 4 | ERT (resistivity) | $15K–$30K | Per-use | After GPR pipeline | WAIT |
| 5 | UAV Thermal | ฿80K–150K | ฿20K–50K | 3–6 months | OPTIONAL |