Deriving water quality indicators from UAV-based sensors to map natural water systems in the Netherlands

By Konstantinos Bampanikos (Greece)

Summary
Since the establishment of the EU Water Framework Directory by the European Commission, water quality has gained great attention by all European Union countries including The Netherlands. Currently, in-situ and space borne remote sensing data are used for the estimation of water quality indicators. The use however, of airborne remote sensing technology can offer great advantages over the existing monitoring techniques.

The aim of the current study was to develop a UAV-based remote sensing approach to derive water quality parameters in small natural water bodies. Chlorophyll-a, turbidity and surface water temperature were assessed. Rikola hyperspectral camera and a thermal consumer camera will be used for the aerial data acquisition. In-situ data were also acquired. Chlorophyll-a and turbidity were locally estimated by the WISP-3 ground sensor and the instantaneous surface water temperature was measured by a laser thermometer.

During this research methods to overcome limitations during the orthorectification and georeferencing steps that are reported by other water related studies associated to UAV remote sensing, were proposed. However still problems were present in both hyperspectral and thermal data processing. Weather condition during the field survey caused problems and limitation at the data processing procedure and analysis. The Hyperspectral UAV images were orthorectified and georeferenced in Agisoft PhotoScan Software and thermal UAV images in ArcGIS. The UAV-based results, after the parameters extraction are realistic compared to the existing field measurements and based on the literature, but no conclusion can be drawn upon their representativeness and accuracy, compared to the WISP-3 data, due to the lack of validation points.

Based on the current results and conclusions, recommendations that should be taken into account for next relevant researches are proposed so that the UAV-added value can be maximized in water quality monitoring applications.

Key words: UAV; remote sensing; water quality; WISP-3