Study area and available data
The Landsat data archive at the U.S. Geological Survey (USGS) Earth Resources Observation and
Science (EROS) Center holds an unequaled 36-year record of the Earth’s surface and is available at
no cost to users via the Internet. Users can access and search the Landsat data archive via the
EarthExplorer (EE)1 2 or Global Visualization Viewer (GloVis)2 3 web sites [12].
Landsat Enhanced Thematic Mapper plus (ETM+) multispectral (MS) and panchromatic (PAN)
images were used in this study. The images have a spatial resolution of 30 m and 15 m respectively.
A subset, 132 km2 in area, was extracted from scene 201/32 acquired on June (2001-2009, except
2003 due to Scan Line Corrector failure in the ETM+). The upper left corner of the subset is placed
at 436507.5 E and 4522312.5 N (UTM geographic coordinates, ZONE 30) for the community of
Madrid (Spain), which contains areas of Mediterranean forest, water bodies and urban areas. For the
year 2005, the whole image was used for NDDI calculation.
For this study, Landsat data for years 2001-2002 and 2004-2009 were selected. The month chosen
was June, since it’s preceded by good rates of precipitation and average temperatures followed
by months with higher temperatures and low rainfall. Climatic data (temperature and precipitation)
characteristic of this zone are shown in Figure 1.