Using Airborne Remote Sensing to Study the Physical Dynamics of Lakes and the Spatial Distribution of Phytoplankton

Abstract

Airborne remote sensing provides an ideal means of mapping the physical structure of lakes and studying the effects of mixing on the horizontal distribution of phytoplankton. Airborne surveys are easier to integrate with field studies than satellite measurements and currently provide the only means of collecting high resolution spectral and spatial data. In this review, I present some results from a series of airborne campaigns organised in the English Lake District between 1986 and 1991. The main instrument used for the surveys was a Daedalus 1268 Airborne Thematic Mapper. This instrument acquires data in 11 spectral bands ranging from the blue visible to the thermal infrared. The visible band data was used to study the spatial distribution of the phytoplankton and the thermal data to map the surface temperature of the lakes. Examples are presented to show how the instrument was used to track the trajectory of surface currents, study exchange processes with the shallow littoral and map the spatial distribution of phytoplankton. Some of the acquired images highlight patterns and processes that could not have been identified by any other means. These included the development of poorly mixed areas (‘dead zones’) in the littoral zone and the effect of power-boat movements on the surface temperature of Windermere. The review describes some of the methods used to process the acquired imagery and includes an introduction to the procedures used to analyse the spectral data now being gathered by a new generation of airborne instruments.