A LIGHTWEIGHT UAV-BASED LASER SCANNING SYSTEM FOR FOREST APPLICATION

Fernanda Magri Torres,Antonio Maria Garcia Tommaselli

doi:10.1590/s1982-21702018000300021

Fernanda Magri Torres, Antonio Maria Garcia Tommaselli

Open Access

https://doi.org/10.1590/s1982-21702018000300021

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Abstract

Abstract Lightweight Unmanned Aerial Vehicles (UAVs) have become a cost effective alternative for studies which use aerial Remote Sensing with high temporal frequency requirements for small areas. Laser scanner devices are widely used for rapid tridimensional data acquisition, mainly as a complementary data source to photogrammetric surveying. Recent studies using laser scanner systems onboard UAVs for forestry inventory and mapping applications have presented encouraging results. This work describes the development and accuracy assessment of a low cost mapping platform composed by an Ibeo Lux scanner, a GNSS (Global Navigation Satellite System) antenna, an Inertial Navigation System Novatel Span-IGM-S1, integrating a GNSS receiver and an IMU (Inertial Measurement Unit), a Raspberry PI portable computer and an octopter UAV. The system was assessed in aerial mode using an UAV octopter developed by SensorMap Company. The resulting point density in a plot with trees concentration was also evaluated. The point density of this device is lower than conventional Airborne Laser Systems but the results showed that altimetric accuracy with this system is around 30 cm, which is acceptable for forest applications. The main advantages of this system are their low weight and low cost, which make it attractive for several applications.

Highlights

Unmanned Aerial Vehicles (UAVs) are becoming a cost-effective alternative to conventional aircraft for aerial image acquisition, mainly in small areas
This paper describes the development and assessment of a system for Airborne Laser Scanning (ALS) onboard small UAVs, as well as the analysis of the resulting data and assessment of pulse penetration in vegetated areas in order to validate the applicability of the system for biodiversity mapping and forestry biomass estimation
The GNSS receiver is responsible for the time synchronization of the laser scanner via Pulse per Second (PPS) signal and National Marine Electronics Association (NMEA) messages sent to the laser unit, which provides synchronization with errors around 1 ms, which is suitable considering the UAV flight speed

Summary

Introduction

Unmanned Aerial Vehicles (UAVs) are becoming a cost-effective alternative to conventional aircraft for aerial image acquisition, mainly in small areas. Small UAVs, weighting less than 20 kg, are low-cost technologies but have limited payload capacity and flight range. As they are compact platforms, the available space for the integration of equipment is limited, requiring smaller and lighter onboard systems to ensure improved autonomy. The use of laser scanner units onboard UAVs can reduce the costs and enable acquisition of data at a higher temporal rate, which could benefit several areas related to environmental monitoring and mapping. This paper describes the development and assessment of a system for Airborne Laser Scanning (ALS) onboard small UAVs, as well as the analysis of the resulting data and assessment of pulse penetration in vegetated areas in order to validate the applicability of the system for biodiversity mapping and forestry biomass estimation

Background

System description

Calibration and quality control

Experiments and results

Findings

Conclusion