RADIANCE OVER BOREAL FOREST STANDS IN NORTHERN SWEDEN AS MEASURED BY THE 79 CHANNEL DAIS-7915 IMAGING SPECTROMETER

摘要

The DAIS 7915 (Digital Airborne Imaging Spectrometer) is a 79-channel imaging radiometer with 73 bands in the 400 nm to 5000 nm spectral range plus 6 thermal bands. During the summer of 1998, the DAIS instrument was flown over several areas in Scandinavia as part of the Swedish Remote sensing for the Environment (RESE) program. This paper reports early results from measurements over two boreal forest sites in northern Sweden. The first site is a well-documented long-term yield optimisation experiment at Flakaliden (lat. 64°07' N, long. 19°27' E) where a large stand of Norway spruce (Picea abies) has been divided into 32 plots (50 × 50 m). Different fertilisation treatments within these plots has resulted in a variation in current annual increment (CAI) from 3 to 22 m~3 ha~(-1) a~(-1), a standing stem volume from 29 to 135 m~3 ha~(-1), and Leaf Area Index (LAI) between 2 and 9 (leaf area per unit ground area). The spectral signatures were plotted for the different fertilisation treatments and compared with the non-fertilised control stands. Spectral features useful for separating treatments were identified. Pixels from the different treatment areas were classified using discriminant analysis with cross validation. The second site is a forest estate called Bratttaker (lat. 64°14' N, long. 19°40' E). Here spectral signatures were analysed to identify features useful for separating tree species in homogenous stands of Norway spruce, Scots pine (Pinus silvestris), and birch (Betula spp.). On a stand level, the correlation between stem volume (m~3 ha~(-1)) and recorded radiance was tested for different bands. A neural network was trained for estimating the volume together with basal area for pine, spruce and deciduous trees using all bands and compared to bandpasses corresponding to the spectral ranges of the Landsat TM sensor.