Harm Bartholomeus
Assistant Professor - Remote Sensing
Wageningen University
Netherland

Biography
Harm Bartholomeus is assistant professor in Remote Sensing at Wageningen University, with a focus on the use of different (remote) sensing systems for precision agriculture and environmental studies. His work ranges from hyperspectral soil spectroscopy, UAV based hyperspectral soil and vegetation studies to structural assessment of tropical forest using terrestrial laser scanning.

Abstract
Design of a UAV-based Hyperspectral Scanning System and Application in Agricultural and Environmental Research

Co-Authors:
Juha Suomalainen, Dr.,Wageningen University - GIRS
Jappe Franke, ir., Alterra - Wageningen UR
Lammert Kooistra, Dr., Wageningen University - GIRS

The use of Unmanned Aerial Vehicles (UAVs) in agricultural and environmental sciences is increasing fast, but the special requirements of the platform in terms of payload and stability ask for the development of dedicated remote sensing instruments. We present the design of a lightweight hyperspectral mapping system (HYMSY), which can be mounted under multicopters with limited payload (system weight = 2 kg). The construction combines off the shelf components and a dedicated processing chain, which produces a) RGB orthophotos, b) a Digital Surface Model which is used for the geometric rectification of c) a hyperspectral image cube. The HYMSY system has been used in ca 200 mapping flights for a multitude of agricultural and environmental applications. Operation of the system over agricultural fields has yielded a number of multi-temporal hyperspectral datasets for several test fields. The results show that the measurements are stable over time, but illumination conditions (direct vs diffuse) have to be considered. Derived products do show the crop development throughout the growing season clearly and correspond well with field measurements. A study in natural environments, aiming at subpixel mapping of plant traits, shows that the quality of the spectral data is good and can be adopted for mapping plant traits and habitat types. Finally, results of flights over (tropical) forests will be shown, where the structural parameters derived from the HYMSY 3D pointcloud will be compared to terrestrial LiDAR measurements. Especially in this kind of forest ecosystems the combination of 3D structural and spectral information is a large added value. Finally, we will present our experiences operating these systems in different environments and the considerations towards legal and safety issues. The complementary value of UAV based geo-spatial data acquisition in relation to satellite imagery and ground sensor networks to support environmental monitoring will be highlighted.