YellowScan illustrates how Instadrone utilized the YellowScan Explorer LiDAR system to gather LiDAR data for modeling four avalanche corridors in the Pyrenees.
Project Overview
This initiative was launched following a request from the Departmental Directorate of Territories, which lacked the necessary LiDAR technology and opted to outsource the data collection to specialized drone firms.
The goal was to create detailed models of four avalanche corridors in the Pyrenees, encompassing an area of 430 hectares (1,060 acres) through a LiDAR survey.
These regions require regular updates to maintain their accuracy and relevance. The primary need was for a LiDAR system integrated with an M300 RTK drone, which would facilitate efficient surveying of the challenging mountainous terrain, characterized by steep inclines, rugged landscapes, and dense forests. The survey covered a distance of 2.3 kilometers (1.4 miles) and included a maximum elevation variation of 1,000 meters (approximately 3,300 feet), representing the most demanding aspect of the project.
Approach
To meet these specifications,Instadrone was assigned the task of collecting LiDAR data using their YellowScan Explorer LiDAR system.
Key objectives included achieving a minimum ground point density of 8 points per square meter (excluding water and buildings) in heavily forested regions, all within a strict timeline. Additionally, the precision (1) of the point cloud was crucial, with a target of 5 cm.
The survey also aimed for an accuracy (2) of the point cloud within 10 cm.
An initial attempt was made using a DJI L1 sensor; however,it fell short of expectations due to various challenges faced during data collection and subsequent processing.
- Avalanche corridor surveyed in the French Pyrenees
- Point cloud of the study area with deciduous and coniferous vegetation
Mission Specifications
- Survey Area:
- Four zones totaling 430 hectares (1,060 acres).
- Timeline:
- Half a day for flight preparations, including decisions on speed, altitude, grid patterns, takeoff points, GCP placements, and backup pivot locations for the IGN reference point.
- Approximately 6 hours of actual flight time.
- Processing took 1 day using POSPac and YellowScan CloudStation, followed by a week dedicated to ground/surface classification in third-party software.
- Flight Count:
- 7 flights: 3 for the largest zone (176 hectares/435 acres), 2 for 148 hectares (366 acres), and 2 for smaller zones.
- Speed and Altitude:
- Flying at 5 m/s at an altitude of 120 m AGL.
- Equipment Used:
- YellowScan Explorer LiDAR system.
- M300 RTK drone.
- Trimble R4S GNSS receiver + CORS network for control.
- POSPac software.
- YellowScan CloudStation with strip Adjustment module.
- No camera was used, resulting in an uncolored point cloud.
vertical slice of the point cloud showcasing highly accurate DTM data
Outcomes
Point density: minimum of 100 points per square meter (varies based on vegetation cover)
Accuracy: between 5 and 10 cm XYZ
Instadrone reported that the point density achieved with the YellowScan Explorer LiDAR system substantially surpassed that of the DJI L1, regardless of whether the surfaces were vegetated or not. Furthermore,Instadrone produced a higher quality point cloud that met the precision and accuracy standards.
The incorporation of the Strip Adjustment feature in YellowScan CloudStation improved the overall consistency between flight lines, resulting in a more accurate modeling outcome.
The YellowScan Explorer effectively managed the entire survey, achieving over 400 meters (1,300 feet) of elevation gain
The client expressed high satisfaction with the results.
As this project, Instadrone has predominantly relied on YellowScan LiDAR solutions. This shift is attributed to the increased confidence in obtaining reliable data, contrasting with the L1 system, which often produced corrupted or incomplete files without clear explanations. Instadrone noted that the integration of pospac within YellowScan CloudStation facilitates seamless post-processing management,allowing flexibility in utilizing a pivot or IGN/CORS reference point. They also emphasized that YellowScan lidar solutions consistently deliver high-quality and dense point clouds, outperforming the L1 system, regardless of vegetation presence. This enhanced performance not only guarantees accurate results but also simplifies subsequent classification tasks.
The advantages of using YellowScan LiDAR systems for this project included:
- Superior quality point cloud.
- Adequate point density even in densely vegetated areas.
- Enhanced comfort for pilots through quicker data acquisition, enabling flights at altitudes of 120 meters (390 feet) and speeds of 10 m/s.
- YellowScan’s post-processing provided complete control over point cloud generation using POSPac.
- The combination of LiDAR and drones minimized human risks, especially in challenging terrains with rugged topography and steep slopes.
“The support from YellowScan was readily available for any major issues. the Support Team is always attentive, provides clear explanations, and is accessible whenever we face challenges, whether through phone calls, TeamViewer, or email,” stated Arthur Marcel, Surveying Technician at Instadrone.
(1) Precision: In LiDAR surveys, precision refers to the standard deviation of the average distance between points and the average plane formed. When combined with mismatch evaluation (plane-to-plane distances between strips), this can provide a good estimation of the overall point cloud noise, which is often mistakenly considered as precision.
(2) Accuracy: In this context, accuracy measures the distance between a point in the acquired cloud and its corresponding point in the reference cloud, offering an assessment of the overall coherence of the survey concerning a given reference. Another method of measuring accuracy would be to utilize GCPs.
