Project Overview

Obstructions to navigable airspace are recurring at the US Air Force Joint Base Lewis-McChord (JBLM) Airfield. Over 90% of the wooded areas surrounding the runway consist of Douglas Fir trees that grow between 3 and 6 feet per year and can reach heights of over 250 feet, penetrating the imaginary approach-departure clearance surfaces.

JBLM is required to conduct airfield obstruction inspections at least once every five years to ensure safe and navigable airspace. According to 14 CFR Part 77, an obstruction to air navigation is defined as an object that exceeds the height of imaginary airspace control surfaces. To guarantee safe aircraft landing and takeoff, the approach-departure clearance surfaces must be kept clear of objects and maintain a glide angle of 50:1 extending out to 500 feet above the runway.

Due to local and state environmental protection laws, airfield management cannot indiscriminately cut and remove Douglas Fir trees. Instead, trees can only be removed after they have been rated, appraised, and marked by a professional forester and classified as an obstruction to airfield operations. With over 1,000 acres of forest extending north and south of McChord Airfield, identifying each tree penetrating the imaginary surfaces is extremely difficult.

In March 2025, a pilot project was organized by the Air Force 627th Civil Engineer Squadron (CES) at JBLM to test and evaluate the use of drone Lidar and cloud-enabled software to inspect 1,000 acres of trees to the north and south of McChord Airfield. Led by Stitch3D with support from Inertial Labs RESEPI, Freefly, and BaseMap, the project was a tremendous success. Using a Freefly Systems Astro (Blue-Certified Drone), RESEPI Lite OS1-64 (NDAA-compliant LIDAR), and Stitch3D cloud software, the project demonstrated the ability to capture and deliver high-quality point cloud data within a 48-hour mission window despite adverse weather conditions.

Project Description

Target Sites

• JBLM North, approximately 250 acres.
• JBLM South, approximately 685 acres.

Mission Window

• 48 Hours (acquisition to delivery and reporting).

Equipment and Software

• Drone: Freefly Astro
• Mapping Payload: Inertial Labs RESEPI Lite OS1 (64)
• Processing Software: Inertial Labs PCMasterPro, Stitch3D Cloud

Deliverable

• Lidar Point Cloud with Ground Classification in project-required coordinate systems.
• Topographic Contour is derived from a classified point cloud in project-required coordinate systems.

Evaluation Metrics

• Timeliness
• Accuracy
• Data Interoperability and Shareability
• Ease of Use

Project Execution

Day 1 Acquisition

Due to bad weather conditions, heavy and intermittent rain, and strong winds of up to 35 miles per hour, the project team chose to cover only the smaller North Site. Flights were executed with the following mission parameters.

• Flight AGL: 55 meters (180 feet)
• Flight Speed: 5.5 meters/second (~12 mph)
• Flight Line Overlap: 35%
• Total Flight Time: 2 Hours
• Validation Survey: RTK Ground Control

Day 2 Acquisition

While the weather was more favorable, the South Site was much larger and mostly covered by dense, tall trees, which blocked stable radio communication between the drone and the remote controller. The project team was forced to execute aggressive battery swaps and utilize three launch locations. Mission parameters were slightly adjusted as follows.

• Flight AGL: 65 meters (213 feet)
• Flight Speed: 8.0 meters/second (~18 mph)
• Flight Line Overlap: 35%
• Total Flight Time: 5 Hours
• Validation Survey: RTK Ground Control

Data Processing

On both days, the collected flight data were immediately processed post-mission. Raw RESEPI data processing was performed in Inertial Labs PCMasterPro. The output point clouds (1.75GB for North Site and 5.58GB for South Site in LAZ format) were then post-processed in Stitch3D cloud to produce ground classification and topographic contour.

Results

Robust assessment showed that the JBLM pilot project produced very high-quality data. Point cloud point density averaged 321 pts/sqm and 329 pts/sqm for the North Site and South Site, respectively. Vertical accuracy (RMSE) was 1.3cm for the North Site and 2.2cm for the South Site. This high level of data quality meets typical land survey standards and exceeds what is required for JBLM airfield tree obstruction detection and mapping.

Conclusion

Despite adverse weather conditions, this project completed the flight coverage of the target JBLM airfield’s North and South approaches in a significantly reduced mission window and delivered high-quality results. All output spatial datasets were made available to 627 CES and 62 OSS stakeholders through Stitch3D cloud in a secure web environment, eliminating interoperability bottlenecks caused by different software and access points.
Based on the success of this pilot project, 627 CES made a strong recommendation that drone Lidar surveys be included as a routine part of airfield inspection operations.

About RESEPI Lite OS1

Powered by Inertial Labs’ advanced INS technology, RESEPI Lite OS1 (64) is a robust, cost-effective, and platform-agnostic Drone LiDAR data collection solution for accuracy-focused survey and mapping professionals, with expanded capabilities for mobile mapping (MMS) and SLAM-enabled scanning in a GNSS-denied environment. Key System Specs are as follows.

• System Vertical Accuracy (5 m/s @ 50 m AGL): 3-5 cm
• Laser Vertical Resolution: 64 channels
• Laser Number of Returns: up to 2
• Laser Points Per Second: 2,621,440
• Laser Instrument Range: 90 m @ 10% reflectivity
• Laser FOV: 360 degrees (Horizontal); +21.2 to -21.2 degrees (Vertical)
• Weight: 1.4 kg (with 24 MP RGB Camera); 1.0 kg (without camera module)
• Dimensions: 20.6 X 16.5 X 14.2 cm
• System Computer: Quad Core with 1 GB RAM and 8 GB eMMC
• Operational Voltage Range: 9 – 45 V
• Power Consumption: 17 W

References

Department of The Air Force, 627th Civil Engineer Squadron (AMC), Joint Base Lewis-McChord. (2025). McChord Airfield Drone LIDAR-Enabled Tree Obstruction Survey.

Stich3D. (2025). Project After Action Report: Joint Base Lewis-McChord Drone Lidar-enabled Airfield Obstruction Survey.

Contacts

Leo Liu (leo.liu@inertiallabs.com), Inertial Labs, a VIAVI Solutions Company

Clark Yuan (clark.yuan@Stitch3D.io), Stitch3D, Inc.

v.2025.05.03