In: Wagner W., Szdkely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
In: Wagner 
108 
and for the Huambo province in Angola, from where there are 
high resolution imagery and/or ground data available. 
2. STUDY AREA AND DATA PREPARATION 
2.1 Study area 
16TTE 16-01= 
Guinea-Bissau (GB) is a country located in the west coast of 
Africa with approximately 36125 km 1 2 . It has a continental 
mainland and a group of islands, the Bijagos Archipelago 
(Figure 1). This country is characterized mainly by a flat land 
surface with altitudes below 100 meters. Two large regions area 
found, namely, the coastal low land area, consisting largely of 
mangroves and swamps stretching from north to south and the 
inland, where open forests, as well as, closed forests dominate 
(especially in the southwest). Savanna woodland is present in 
the northern and eastern regions of the country (White, 1983). 
This distribution is dependent on different soils characteristics 
and mainly on differences in rainfall regimes between north and 
south, and east and west (Catarino, 2004). Two marked seasons 
can be observed in this region, characterized by a tropical 
climate: a dry season between November and April and a wet 
season between May and October. 
The Huambo Province is located on the central plateau of 
Angola (Figure 1) and has an area of about 34270 km 2 (USAID, 
2008). The region includes the higher mountains and the 
highest peak in Angola, the Moco Mountain with an elevation 
of 2620 meters, and has a wet season from October and April 
and a dry season between May and September. The dominant 
vegetation is mainly composed of miombo and savanna 
woodlands, with grasslands covering large areas of lower 
drainages. The miombo floristic formation is dominated by three 
species, Brachystegia spp., Combretum spp. and Julbemardia 
spp, whereas in savannas there is a dominant grass layer with 
Hyparrenia spp and Androgon spp.. 
2.2 Landsat data and Field data 
For GB, a dataset of five scenes per date of Landsat Thematic 
Mapper (TM) and Enhanced Thematic Mapper (ETM+) was 
used for 1990, 2002 and 2007, in a total of fifteen images. The 
images were from the late dry season, except for 1990. A 
geometric correction was performed with ground control points, 
resulting in a RMS error less than 1 pixel. The data were 
resampled into Universal Transverse Mercator projection Zone 
28 north, datum WGS84 with a spatial resolution of 25 meters. 
Field data were collected in GB for Mangrove, Closed forest, 
Open forest and Savanna-woodland, in 293 geo-referenced 
sample plots selected from a stratified random origin regular 
net, surveyed in three campaigns conducted in 2007, 2008 and 
2009. These data were used for classification accuracy 
assessment. 
For Huambo, a dataset of four images per date of Landsat TM 
was available, free of charge, for the period 1990/1991/1992 
and 2000/2001/2002 from the University of Maryland’s Global 
Land Cover Facility (http://glcfapp.umiacs.umd.edu/) and 
Landsat ETM+ data was available for 2008/2009 from the U.S. 
Geological Survey (USGS) Earth Resources Observation 
Systems (EROS) Data Center (EDC) (http://glovis.usgs.gov/). 
The Landsat images were, already, geometrically corrected to 
the Universal Transverse Mercator projection Zone 33 South 
and with a spatial resolution of 30 meters. 
A few forest inventory plots in areas of forest and savanna were 
collected within the Huambo province and were later used in 
the classification verification. 
2.3 Global land cover maps 
Land cover data, produced by three international initiatives 
(IGBP, GLC2000 and MODIS) were freely available for this 
study. The International Geosphere Biosphere Project (IGBP 1 ) 
(Loveland et al., 2000) distinguishes 17 land cover classes 
according the science requirements of IGBPs core projects and 
was produced based on NOAA-AVHRR imagery from 1992- 
1993, at a spatial resolution of 1 km. 
The Global Land Cover 2000 (GLC2000 2 ) (Fritz et al., 2003) 
distinguishes 22 land cover classes, developed based on the 
Land Cover Classification System (LCCS) and was derived 
from 1 km SPOT4-VEGETATION daily data from November 
1999 to December 2000. 
The maps produced using the Moderate Resolution Imaging 
Spectroradiometer (MODIS 3 ), (Strahler et al., 1999) adopt the 
IGBP legend, and have two types of products, one based on 
Terra (T) satellite data and one based on Aqua and Terra 
combination (AT) satellite data, with a spatial resolution of 1 
kilometre and 500 meters, respectively. The last one was 
converted into a 1 Km grid database to have the same cell size 
of the other global land cover products. These datasets were 
produced annually since 2001 until 2007, and in this study two 
maps were used for GB in 2002, one from Terra 
(MODIST2002) and one from Aqua/Terra combination 
(MODISAT2002). Another one was used for 2007 
(MODISAT2007). For Huambo, also, two maps were used from 
2001 (MODIST2001 and MODISAT2001) and one from 2007 
(MODIS AT2007). 
3. METHODS 
3.1 Landsat land cover maps (LAND maps) 
A legend with ten land cover classes was established for the 
Landsat image classification in GB: Closed-forest, Open-forest, 
Savanna-woodland, Mangrove, Grassland, Croplands/Bare soil, 
Wet-vegetation, Burnt, Water, and Sand. This legend was 
defined according to expert knowledge and pre-existing maps at 
different scales. This information was used to train a supervised 
classification tree algorithm. Three Land cover maps were 
obtained for 1990 (LAND90), 2002 (LAND2000) and 2007 
(LAND2007). Classification accuracy was assessed using data 
collected in the field between 2007 and 2009 for four vegetation 
classes: Mangrove, Closed Forest, Open Forest and Savanna- 
woodland. 
1 http ://edc2 .usgs. gov/glcc/tabgeoglobe.php 
2 http://bioval.jrc.ec.europa.eu/products/glc2000/products.php 
3 https://wist.echo.nasa.gov/ 
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