Han River Bridge Inspection in Seoul With XGRIDS Lixel L2 Pro

Case Studies2026.06.115 min read

A single round-trip by boat, delivering 3D data ready for engineering workflows.

Project by SQ Engineering. Adapted from a field report by T3solution.

A Next-Generation Bridge Inspection, Completed With the Lixel L2 Pro

Bridge inspection is among the most demanding tasks in digital twin work. The underside of a bridge is especially difficult: drone flight is constrained, and GPS shadowing, strong winds, and obstructions make stable data capture hard to achieve. On this project, the team used the XGRIDS Lixel L2 Pro to record the entire bridge in 3D using a safer and more efficient method than the conventional approach.

Operator capturing the Han River bridge underside from a boat with a handheld Lixel L2 Pro scanner

Colored point cloud of the full Han River bridge deck and piers from a single scan

Parameter	Value
Scan time	~30 minutes
Bridge length	~1.2 km
Scan speed	2–3 m/s
Capture method	Single round trip by boat under the bridge

The Limits of Conventional Underside Scanning

3D laser scanning point cloud of the bridge underside and V-shaped piers

Standard methods for scanning a bridge underside carry several problems:

Drone access is difficult, which restricts the available flight paths
Drone stability drops in GPS-shadowed sections
Ground equipment can't reach many areas, leaving blind spots
Producing a precise model takes significant time and labor

Structurally complex sections, like inside truss members and under girders, are particularly hard, because securing a viable drone flight path is a problem in itself.

How the Lixel L2 Pro Changed the Approach

This project used the Lixel L2 Pro, XGRIDS' multi-SLAM LiDAR scanner. A complete scan of the bridge underside was fully captured without a drone.

Boat-based scanning beneath the Han River bridge for as-built bridge inspection

1. Multi-SLAM — Complete 3D Data From a Single Round-Trip Scan

The Lixel L2 Pro's Multi-SLAM runs several SLAM engines in parallel, enabling stable pose estimation even in GPS-denied environments. On site, the practical advantages were:

Top-down view of the single round-trip scan trajectory mapped along the bridge deck

One round trip captures the full dataset. The operator simply travels the bridge underside once and back by boat:

No complex route planning
No drone-related risk or permitting
Minimized SLAM drift, so no layering artifacts in the data
Stable capture even around structural curves and blind spots

Generating high-quality 3D data from a simple capture path is a notable strength of the Lixel L2 Pro among SLAM devices.

2. RTK — Absolute Coordinates Built Into the Data

RTK-georeferenced bridge model colored by elevation and aligned to a map base for digital twin use

The Lixel L2 Pro supports RTK (Real-Time Kinematic). This writes accurate absolute coordinates directly into the captured point cloud, which means:

Reduced setup, with no need to place ground control points
Immediate GIS analysis without coordinate correction
Direct connection to digital twin, BIM, and structural analysis workflows
Lower time and cost

In short, the scan data can be used as a digital twin aligned to real-world space, with no separate registration step.

How the Point Cloud Is Used in Bridge Inspection

The high-density point cloud from the Lixel L2 Pro is not just a visualization. In inspection and maintenance work, it serves as core engineering data.

1. Bridge Geometry and Cross-Section Analysis

The point cloud supports accurate measurement of cross-sections, girder height, width, and incline.

Point cloud cross-section measuring a 93 m bridge span between piers for as-built documentation

Top-down cross-section measuring the roughly 20 m bridge deck width from the survey data

2. 3D Digital Twin Inspection

Intensity-colored cross-section of a bridge pier captured by lidar

Working from the high-density 3D model, the team can:

Visualize crack locations
Check displacement and deflection
Identify member deformation or distortion
Track change over time by comparing against prior datasets

Comparing scan data collected across multiple years makes it possible to quantify deterioration trends.

3. Accurate Records of Hard-to-Reach Areas

Areas that are difficult or unsafe to access — the top of girders, the inside of truss members, around pipework — can be recorded precisely as point cloud data, enabling safer inspection.

Colorized point cloud of the bridge underside and pier viewed from a low angle

4. Mesh and Splatting Conversion for a Virtual Inspection Environment

The point cloud from the Lixel L2 Pro can be converted through post-processing into:

3D Mesh
3D Gaussian Splatting

This lets inspectors review the structure in PC, VR, or web environments as if walking through the bridge itself — a level of detail that paper drawings and 2D photos can't capture.

Textured 3D mesh of the Han River bridge underside, girders and piers reconstructed from Lixel L2 Pro point cloud data

Figure: 3D Mesh — textured mesh reconstruction of the bridge underside and pier.

Photorealistic 3D Gaussian Splatting view from water level showing the Han River bridge piers and Seoul skyline

Figure: 3D Gaussian Splatting — photorealistic splat reconstruction viewable in browser

A New Standard for Bridge Inspection

On this project, the Lixel L2 Pro demonstrated:

Full 3D scanning of the bridge underside without a drone
Complete capture in a single boat round trip, via Multi-SLAM
An RTK-georeferenced digital twin generated immediately
A point cloud usable across the full maintenance lifecycle
Extension into multiple 3D formats, including mesh and Gaussian splatting

The result is a single field workflow that produces georeferenced, engineering-usable 3D data for bridge inspection — without the access constraints and blind spots of drone-based capture.

With thanks to SQ Engineering for sharing this case.