Landscapes Forest and Global Change - ESA - Escola Superior ...

J. Schaefer-Santos & C. Lingnau 2010. Landscapes in Transition – Monitoring in Areas of Landslides
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2.1 Change Detection
The purpose of applying the techniques of change detection is within a set of pixels, identifying
those that are significantly different between the first and last image in sequence (Radke et al.
2005). Select the image start (t1) and the final image (t2), where the procedure is repeated
between pairs “t 2 – t 3 ” e “t 4 – t 3 ” , generating three classified images (Change Detection 1 – CD 1 ,
Change Detection 2 – CD 2 e Change Detection 2 – CD 3 ). The classification of this study followed
values change between -5 and +5. Changes close to zero (from -2 to +2) were ignored,
representing "no change", and "abrupt change" were identified as increased and reduced
biomass. We used the simple difference method and the percentage difference between
Vegetation Index on four occasions (t1, t2, t3 and t4) as follows (1):
D( x)
= t2 ( x)
− t1(
x)
(1)
Onde:
D(x) = classified image by simple difference;
t 2 (x) = vegetation index in the final time of the analysis;
t 1 (x) = vegetation index in the inicital time of analysis.
3. Results
In the study area can easily locate the areas of landslides and areas with sediment deposition by
staining differentiated image 4 (2009), with values close to zero, which represents a lack of
vegetation. In this same place, it was observed that the vegetation index have no color
differentiation mean that deforestation in the years before the landslide (Figure 2). Figure 3
shows the image obtained of the changes between 2007 and 2009 (CD 3) which can be observed
in the landslide area and increasing the forest cover.
Figura 2: Change detection occurred in the area of landslides since 1992 to 2009.
Forest Landscapes and Global Change-New Frontiers in Management, Conservation and Restoration. Proceedings of the IUFRO Landscape Ecology
Working Group International Conference, September 21-27, 2010, Bragança, Portugal. J.C. Azevedo, M. Feliciano, J. Castro & M.A. Pinto (eds.)
2010, Instituto Politécnico de Bragança, Bragança, Portugal.