Underground Utility Mapping — ABC Industrial Park
Objective: locate metallic & non-metallic utilities and verify pavement structure over a 20,000 m² area. Deliverables included georeferenced utility plan (DXF), radargrams, and a concise engineering report for design & excavation planning.
Scope & Site Conditions
Scope
- Grid-based GPR survey at 1 m spacing, tighter (0.5 m) near utilities.
- Utility detection: water, sewer, electrical, telecom (metal & non-metal).
- Slab/base thickness estimation and void screening along loading bays.
Conditions
- Surface: paved asphalt + concrete; moderate rebar density near bays.
- Soil: sandy clay; moisture after light rain → moderate attenuation.
- Access: live facility; safety induction & escort required.
Methodology & Workflow
1) Planning & Control
Established site grid with total station control; integrated GNSS tracklogs for georeferencing. Reviewed as-built records to prioritize corridors.
2) Data Acquisition
Ran 250–400 MHz antennas for depth and 900 MHz for high-detail near buildings. Line spacing 1.0 m (0.5 m at critical zones). Stacking, time-window, and sampling optimized per substrate.
3) Processing
Background removal, dewow, gain correction, migration (where appropriate), and depth conversion using site-calibrated velocity (v ≈ 0.09–0.11 m/ns).
4) Interpretation & Validation
Picked hyperbolas and layer breaks; cross-checked with EM locator & visible features. Spot-checks with test pits at two locations (client-approved).
5) Reporting & Delivery
Compiled utility plan (DXF + PDF), annotated radargrams, depth slices, and recommendations for excavation safety.
Equipment
Antenna Suite
250 MHz & 400 MHz (depth to several meters in favorable soils), 900 MHz for concrete details (0–0.4 m).
Control Unit
High-rate sampling, trace stacking, real-time marking, integrated GNSS logging.
Software
2D/3D processing, migration, time/depth slicing, CAD/GIS export (DXF, SHP, GeoJSON).
Safety
- Non-ionizing, low-power RF. Operated within manufacturer & local guidelines.
- Work permits, barricading near active driveways, spotters for traffic.
- PPE: helmet, safety shoes, high-vis, gloves.
QA/QC
- Daily instrument checks & time-zero calibration.
- Velocity validation using known depths / cores where available.
- Independent review of picks; versioned processing logs.
Results & Findings
Highlights
- Mapped 14 utility corridors; identified 3 undocumented crossings.
- Detected voiding beneath slab near Bay-4 (~0.25–0.35 m depth).
- Provided slab/base thickness model for pavement rehab design.
Example radargram: hyperbola fits and depth conversion annotations.
Gallery
Downloads & Deliverables
Files are georeferenced; coordinate system: UTM 43N. Include DXF in CAD with provided layer styles.
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