eesti teaduste
akadeemia kirjastus
Estonian Journal of Ecology
Calibration of time series of satellite images to study the seasonal course of forest reflectance; 5–18

Tiit Nilson, Tõnu Lükk, Sandra Suviste, Heidi Kadarik, Alo Eenmäe
A seasonal series of Landsat TM and SPOT images over a forest area at Järvselja, Estonia, was compiled from the set of images acquired in 1986–2003 to study the seasonal changes in reflectance among different forest types. All images were transformed into ground-level reflectance factor units and the seasonal courses of reflectance were constructed for several forest types in six reflective bands of Landsat TM. Different forest types were extracted by respective queries from the forestry database of Järvselja. The seasonal time course was presented as a function of temperature time. The calibration coefficients of all images in the series were corrected to obtain a smooth seasonal course of reflectance for fertile stands dominated by spruce, pine, and birch as dark targets, and Pinus bogs as bright targets. The smoothed seasonal series of reflectance are now suitable for a further quantitative analysis for the main driving factors.

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