Objective sampling design in a highly heterogeneous landscape - characterizing environmental determinants of malaria vector distribution in French Guiana, in the Amazonian region

Table 1 Complementary geographic information layers, data sources and attributes extracted for landscape characterization

Geographic information layer	Information source	Method for layer creation	Remarks	Attributes extracted for virtual sites	Variable group
Buildings				Minimum distance to, Number^c	Anthropization
Asphalt roads, trails	Air photographs^a	Manual digitizing (digitizing scale ≈ 1/5400)	Roads/trails accessible with a four-wheel drive vehicle	Minimum distance to (m), Length (m)^c
Greenhouses				Minimum distance to, Number^c
Anthropogenic basins	Air photographs^a and BD-Carto®;^b		Basins may or may not be permanently flooded	Minimum distance to (m), Surface proportion^c
Gold mining sites	Air photographs^a and SPOT5 satellite images	Manual digitizing		Minimum distance to (m)
Permanent rivers (excluding the Comté River)	BD-Carto®;^b			Minimum distance to (m), Length (m)^c	Hydrology
Temporary rivers (excluding the Comté River)	BD-Carto®;^b
Banks of the Comté River	Land cover map	GIS^d computation from the land cover map
Natural water surfaces	Air photographs^a and BD-Carto®;^b		May or may not be permanently flooded	Minimum distance to (m), Surface proportion^c
Floodplains			Temporarily flooded
Altitude				Altitude (m)	Topography
Aspect (positive angle, in degree, relative to a west-east line)	SRTM^e Digital Elevation Model	GIS^d computation from SRTM data		West-East orientation (cosine), South-North orientation (sinus)
Slope				Slope (%)

^aAerial photographs from BD-Ortho®; 2006 product (IGN, the French National Institute of Geographic and Forest Information).
^bBD-Carto®; 1:25,000 scale map (IGN product, 2006).
^cAttribute extracted within a 200 m radius buffer, centered on the virtual collection site.
^dGIS: Geographic Information System. The fee and open software used is GRASS GIS[18].
^eSRTM: Shuttle Radar Topography Mission (90 m spatial resolution).

ISSN: 1472-6785