High-Accuracy LiDAR & Aerial Survey for a Diamond Mine in Lesotho

Project Overview: Kao Mine Aerial Survey

3DroneMapping was appointed by Storm Mountain Diamonds Company to carry out a high-accuracy aerial survey at Kao Mine, located approximately 25 km west of Letseng in Lesotho.

The project covered an area of approximately 315 hectares and required the delivery of orthophoto imagery, LiDAR point clouds, contours, and a high-resolution digital terrain model (DTM). The survey was completed to strict accuracy requirements suitable for mining, engineering, and planning applications.

Establishing Accurate Ground Control

To achieve centimetre-level accuracy, a robust ground control network was established across the site.A total of 12 permanent ground control points and additional quality check points were installed and surveyed to better than 20 mm accuracy.

Control points were carefully positioned to ensure:

• clear sky visibility,

• long-term stability,

• accessibility,

• and minimal risk of disturbance during operations.

This control network allows for reliable verification of final data accuracy and provides a solid reference framework for future surveys at the site.

Advanced Survey Equipment & Custom UAV Platform

All flight operations were conducted using a custom-designed rotory-wing UAV, developed and built in-house by the 3DroneMapping R&D team.

The aircraft was equipped with:

• a 60 MP calibrated metric RGB camera,

• a LiDAR INS system with dual-frequency GNSS and IMU,

• and a LIVOX Avia LiDAR sensor capturing up to 720,000 points per second.

This configuration allows for highly accurate position and orientation tracking, enabling direct georeferencing and reducing reliance on heavy ground control.

Precision Flight Planning & Data Capture

Flights were planned to meet a 3 cm accuracy target, with:

• 70% forward overlap

• 55% sidelap

• flown at approximately 120 m above ground level

Despite challenging mountainous terrain and potential signal interference, flight operations ran smoothly using long-range communications and frequency-hopping systems.

The full survey was completed in a day, covering 24 km of flight lines in just 70 minutes, under ideal weather conditions.

LiDAR & Photogrammetry Processing

Post-processing was completed using industry-standard software, including NovAtel Inertial Explorer, Terrasolid, and Inpho.

Key processing steps included:

• precise GNSS-IMU trajectory computation (PPP & PPK),

• direct georeferencing of imagery,

• dense LiDAR point cloud generation,

• ground classification and DTM creation,

• orthorectification and radiometric balancing of imagery.

Quality control checks confirmed excellent results, with trajectory deviations never exceeding 15 mm in position.

Final Accuracy & Deliverables

The final dataset exceeded the client’s accuracy requirements:

• Average LiDAR density: >80 points/m²

• Orthophoto resolution: 5 cm GSD

• Vertical accuracy: better than 1.5 cm (1-sigma)

All data was delivered in WGS84 (WG29) with orthometric heights referenced to the South African Land Levelling Datum.

Delivered products included:

• Orthophotos (ECW)

• LiDAR point clouds (LAZ)

• Digital terrain models (ASCII)

• 1 m interval contours (DWG)

Supporting Mining & Engineering Decisions

This project demonstrates how high-accuracy drone LiDAR and aerial surveying can deliver reliable terrain data for mining operations, feasibility studies, planning, and infrastructure design, even in challenging mountainous environments.

If you require survey-grade aerial data for mining, engineering, or large-scale land development projects anywhere in Southern Africa, 3DroneMapping has the experience, equipment, and in-house capability to deliver.

👉 Contact us to discuss your next aerial survey project.