I. Background and Challenges

The 2024 Noto Peninsula earthquake struck Ishikawa Prefecture, Japan, on January 1, with a magnitude of 7.6, triggering more than 2,300 landslides across the affected region. Rapid and accurate terrain data acquisition was critical for emergency response and recovery planning.

The survey was conducted at two landslide sites in Mitsui-machi, Wajima City, including a single large slope failure affecting downstream residential areas and farmland, as well as a multi-landslide site where sediment flowed into mountain streams and agricultural land.

However, surveying in forested disaster areas presented major challenges:

• Traditional surveying methods (e.g., total stations) are too time-consuming for large-scale disaster response

• UAV photogrammetry is significantly affected by tree canopies, making it difficult to obtain terrain data within forested areas

• Surveying on dangerous mountain slopes poses safety hazards

• Multiple landslides and fallen trees create complex terrain, making accurate ground data acquisition difficult

II. Solution: SLAM LiDAR Scanner for Rapid & Safe Data Capture

SLAM (Simultaneous Localization and Mapping) enables continuous point cloud generation by matching real-time LiDAR observations with previously captured features, allowing accurate mapping while moving — without traditional static instrument setup.

In this project, GreenValley International LiGrip H120 Handheld SLAM LiDAR Scanner was deployed to efficiently capture large-scale, complex terrain data. LiGrip H120 offers flexible operation modes and robust positioning performance in both GNSS-covered and challenging environments.

III. Implementation Process

Workflow

The client used the LiGrip H120 handheld 3D scanner along planned routes: route planning → on-site scanning at walking speed → real-time preprocessing (GreenValley APP) → post-processing (LiDAR360MLS) → final deliverable production.

On-Site Scanning Best Practices

Hold the scanner steadily at chest level with both hands, avoiding swinging or tilting. Choose start/end points with multiple route options.

When transitioning between spaces, enter slowly with sideways steps and pause briefly to capture features from both areas. Walk slowly indoors, make smooth curved turns, and pause ~5 seconds at doorways to capture both sides.

Operation Time Comparison

Survey content: Centerline and longitudinal section measurement 500 m, structure planning site cross-section measurement 50 m.

The data shows that LiDAR SLAM and UAV photogrammetry have essentially the same operation time, but total station surveying requires approximately twice the operation time compared to ICT-based surveying. Particularly for on-site work, total station surveying requires 6 hours, while ICT-based surveying can be completed in approximately 1 hour.

IV. Solution Summary

Quantified Results

By adopting the GVI LiGrip H120 handheld scanner and LiDAR SLAM surveying solution, the client achieved:

• Approximately 83% reduction in on-site operation time: from 6 hours with total station to approximately 1 hour

• Over 50% improvement in overall operational efficiency: total operation time reduced from 10 hours to 4-5 hours

• Effective acquisition of sub-canopy terrain data: solving the vegetation obstruction problem of UAV photogrammetry

• Measurement accuracy comparable to total station: suitable for design-level engineering applications

• Significantly improved safety: reduced operation time on dangerous mountain slopes

Applicable Scenarios

LiDAR SLAM technology is particularly suitable for the following survey types:

• Streams (Valley Engineering): Unaffected by tall tree canopies, direct laser measurement of ground surface

• Landslide Sites (Small to Medium Scale): Can capture micro-topography and slope crack details

• Forest Road Disasters: Can conduct comprehensive surveys including landslides

• Structure Measurement: Can freely acquire high-density point clouds from various angles for inspection and damage assessment

Client Feedback

"UAV photogrammetry has advantages in wide-area data acquisition and can safely obtain data after disasters without entering dangerous sites. On the other hand, LiDAR SLAM surveying can acquire sub-canopy terrain data that is difficult to measure with UAV photogrammetry. In forest area surveys, vegetation impact has always been a challenge, but since LiDAR SLAM measures from near ground level, it can avoid the effects of vegetation, especially tree canopies. By applying these surveying methods, terrain data can be acquired more quickly and safely, contributing to improved operational efficiency and safety in disaster site surveying operations."

— Kazuki Okutani, Senior Engineer, Osaka Branch, Forest Technology Company