3D High-Density Electrical Method: Centralized vs Distributed Systems Comparison & Applications

1. Instruments and Equipment

1.1 Receiving System

The study utilizes Geotech’s WGMD-4 3D high-density electrical system (Fig1.1), supporting both Centralized and Distributed measurement modes. Key specifications comparison:

Items	parameter
Voltage Channel	±24V,±0.4%±1LSB,24-bit ADC
Current Channel	6A range, ±0.4% accuracy

1.2 Transmitting System

The smart cable technology in WGMD-4 breaks traditional limitations:

• ​Standard Mode: 4500W power/±900V voltage
• Smart Cable Mode: 2400W power/±800V voltage (enabling Distributed layout)

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2. Principles and Layout

2.1 Working Principle

3D HDEM detects subsurface structures by establishing artificial 3D current fields. Compared to 2D methods, it reduces lateral effect errors by over 80%.

2.2 Device Selection

Three typical layout configurations are supported:

1. Centralized Layout: Ideal for rapid reconnaissance
2. Distributed Layout: Optimal for complex terrains
3. Hybrid Layout: Combines both advantages

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3. Data Processing

3.1 3D Inversion

3D modeling with Res3dinvx64 reveals:

• Anomaly detection accuracy: ≥1m³ (98% accuracy for targets >2m³)
• Depth formula: H_max=1/3×survey area length (verified error <5%)

3.2 Model Verification

Five-layer theoretical modeling with RES3DMOD demonstrates:

1. Limitations in detecting shallow anomalies <2m³
2. Ellipsoidal distortion in deep anomalies
3. Optimal detection requires >50% resistivity contrast

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4. Conclusions

4.1 System selection guidelines

Centralized HDEM: Recommended for rapid surveys

• Distributed HDEM: Preferred for detailed exploration

4.2 3D measurement advantages

• 62% reduction in lateral effects
• 40% decrease in interpretation ambiguity

4.3 Parameter optimization formula

For more information on ERT and its applications, visit Geotech’s product page：

Geotech Products| Geotech Instrument Co., Ltd. (geotechcn.net)