Mapping the City's "Lifeline": Lixel L2 Pro Assists in Surveying a 8km Underground Pipe Corridor

Case Studies2025.02.215 min read

XGRIDS’ partner deployed the Lixel L2 Pro handheld 3D scanner, enabling high-precision mapping to support project validation and acceptance.

Underground utility corridors, often referred to as the "lifelines" of a city, house essential infrastructure such as electricity, telecommunications, and water supply systems. These complex networks require accurate surveying and mapping for both construction and maintenance.

Following the completion of a 8-kilometer-long underground pipe corridor in Ningbo, a comprehensive as-built survey was required. With an average depth of 15–20 meters below ground, the project presented significant technical challenges. To tackle this, XGRIDS’ partner deployed the Lixel L2 Pro handheld 3D scanner, enabling high-precision mapping to support project validation and acceptance.

01 | Challenges in the Field

Narrow & Constrained Space

The pipe corridor, measuring just 1.3 meters in width, presented significant mobility constraints. Traditional total stations were difficult to position, requiring frequent relocations that slowed down the survey process.

Featureless Environment

With its long, repetitive structure and lack of distinct reference points, the underground corridor posed challenges for SLAM-based mapping, making it prone to trajectory drift and data misalignment.

Surveyor walking an 8 km underground utility corridor with a handheld Lixel L2 Pro scanner

Large-Scale Mapping Constraints

Surveying 8 kilometers using conventional total stations would require extensive time and labor. Additionally, long-distance scanning in a mobile SLAM workflow risks error accumulation, affecting overall data accuracy.

02 | Solution: Lixel L2 Pro for High-Precision Underground Scanning

1. Lixel L2 Pro: Real-Time 3D Scanning & Modeling

As XGRIDS' flagship handheld scanning device, the Lixel L2 Pro leverages its proprietary Multi-SLAM algorithm to enhance scene adaptability and mapping reliability. Even in sparse-feature environments like underground pipe corridors and tunnels, it ensures stable and accurate mapping.

Operator scanning the narrow pipe corridor in a single-pass handheld SLAM workflow

2. Establishing Ground Control Points for Absolute Accuracy

To ensure positional accuracy, ground control points (GCPs) were projected into the underground corridor using a laser vertical alignment instrument. A total of 75 control points (placed every 100 meters) were established along the 8km scanning path, allowing the relative coordinate system to be converted into an absolute coordinate system via total station survey.

Colorized point cloud of the underground corridor interior with pipes and walls

3. Segmented Scanning With Real-Time Data Validation

The corridor was divided into 13 sections, with data collected in segments using the Lixel L2 Pro. The real-time color point cloud provided instant feedback, ensuring no drift or misalignment before completing the scan of each section.

Scanning trajectory and point cloud following the curving pipe corridor path

4. Direct RCS Export for Seamless CAD Integration

Point cloud data was processed in LixelStudio, ensuring precise alignment with no layering or misalignment. The color point cloud provided a detailed and realistic reconstruction of the underground environment, allowing all corridor features to be visualized clearly.

The processed point cloud was converted to RCS format in LixelStudio, enabling direct import into CAD software for floor plan drawing. The color point cloud helped distinguish structures, reducing object recognition errors.

Corridor point cloud imported into CAD as an RCS file for floor-plan drafting

03 | Key Advantages of the Lixel L2 Pro Solution

Stable Performance in Featureless Environments

The Lixel L2 Pro combines LiDAR and visual sensors for Multi-SLAM positioning, maintaining stability in sparse-feature, repetitive structures without requiring manually placed feature points. No drift, no misalignment with the deliverables, and data accuracy meet high-standard underground mapping requirements.

Lightweight & Optimized for Confined Spaces

Designed as a handheld device, the Lixel L2 Pro eliminates the need for station setups or frequent repositioning, making it ideal for tight spaces like pipe corridors. Unlike total stations that struggle with obstructions, the Lixel L2 Pro ensures seamless data capture with full structural coverage.

Seamless Software & Hardware Integration for Efficiency

The real-time point cloud can be reviewed instantly via mobile phones and laptops, allowing users to validate the scans of key areas on-site. With LixelStudio, post-processing is streamlined—data is directly output in RCP format, ready for CAD integration, minimizing data processing time and maximizing workflow efficiency.

04 | Customer Feedback

The client praised the Lixel L2 Pro for its stability and accuracy in the sparse-feature pipe corridor environment. Compared to traditional methods, the real-time handheld LiDAR scanner significantly improved efficiency while maintaining high precision. The final dataset was well-received by project stakeholders, acknowledging its value in expediting the project acceptance process.

Conclusion

The Lixel L2 Pro handheld scanner has proven to be a game-changer for underground infrastructure mapping, delivering a fast, accurate, and efficient alternative to traditional methods. By eliminating complex station setups and integrating seamlessly with CAD workflows, it is redefining how large-scale underground projects are surveyed and documented.

📍 Learn More

Discover how XGRIDS technology is transforming geospatial mapping and underground surveying. Visit www.xgrids.com for more details.