Table 3.

Technical specifications of the FRA 2000 and TREES II strategies for sampling and interpretation.

	FRA 2000 (RS)	TREES II
domain	dry and humid tropics	humid tropics
dates	1980, 1990, 2000	1992, 1997
sampling strategy	two-stage stratified random sampling based on regions and forest cover	two-stage stratified random sampling based on regions, deforestation hot spots and forest cover
sampling frame	Landsat reference system	hexagonal tessellation (equal-area)
sampling units	117 (population=1203)	104 (population=740)
imagery	Landsat full scenes	Landsat (full and quarter scenes according to the landscape complexity)
interpretation	visual interdependent interpretation	visual interdependent interpretation
legend	2 levels: 9 fixed classes+12 options	hierarchical scheme (life form, cover, water regime…)
digital files	grid 2×2 km2	full interpretation
aggregation	continent, global, ecological zone	continent, global