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Research article - Peer-reviewed, 2008

Change detection of thinned Norway spruce stands using optical SPOT-4 satellite data

Magnusson, Mattias; Fransson, Johan E. S.; Olsson, Hakan


The possibility to detect thinning of Norway spruce (Picea abies) stands using multitemporal SPOT-4 satellite data was investigated. The test site is located in southern Sweden (58 degrees 30'N, 13 degrees 40'E). A field inventory was carried out for 20 stands subjected to mechanical tree thinning and 17 unthinned stands. The reduction in forest stem volume was on average 20%. SPOT satellite data from the years 2000 and 2002 (before and after the thinning) were radiometrically normalized and a difference image was computed. Pixel values from the difference image showed that the reflectances were significantly lower in the near-infrared band for the thinned stands compared with the unthinned stands. In addition, an increase in the mid-infrared band was observed for the thinned stands. However, no significant change could be detected in the green or red bands. Discriminant analysis using a combination of bands in the difference image and the image acquired prior to thinning showed that approximately 83%-95% (using between 2 and 6 bands) of the stands could be spectrally separated. For practical applications, detection of thinnings could be useful for improving the efficiency of timber harvest accounting.

Published in

Canadian Journal of Remote Sensing
2008, Volume: 34, number: 5, pages: 431-437