Forest Terrain Mapping After the Japan Earthquake

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

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.

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 👉 Planning surveys in forested or GNSS-challenged disaster areas? Talk to our team at info@greenvalleyintl.com to learn how LiDAR SLAM can complement UAV and total station workflows.