The time series of maps is showing three differnt forage parameters (green biomass, metabolisable energy, metabolisable energy yield) from 04.12.2015 to 29.09.2016. The covered area matches the Vea catchment at the border region of Ghana and Burkina Faso.

For model calibration, data was collected during the rainy season 2012 at 21 sites spread along a north-south climate gradient reaching from northern Ghana to central Burkina Faso. Spectral reflectance measurements of vegetation plots were performed using a FieldSpec 3 Hi-Res Portable Spectroradiometer (ASD Inc., Boulder, CO, USA). Partial least squares regression was used to calibrate spectral models between reflectance data and forage characteristics (green biomass & metabolisable energy). Metabolisable enrgy yield was calculated based on the other two forage parameters. For more details regarding sampling design and model calibration, see Ferner, Linstädter et al. (2015).

Sentinel-2 images were acquired for twelve dates. Imagery was atmospherically corrected using the plugin ‘sen2cor’ within the SNAP toolbox, provided by the European Space Agency (ESA).

To assure that forage models were only applied on vegetated areas, a vegetation mask was build based on MESMA (multiple endmember spectral mixture analysis) and only pixels with a fractional cover of green vegetation of more than 30% were used. Finally, forage provision models resampled to Sentinel-2 spectral resolution were applied to obtain maps of estimated forage provision.

Further information:

Ferner, J., Linstädter, A., Südekum, K. H., & Schmidtlein, S. (2015). Spectral indicators of forage quality in West Africa’s tropical savannas. International Journal of Applied Earth Observation and Geoinformation, 41, 99-106.