The forest cover data tiles are generated from the Global Forest Change dataset.
First the the geographic areas of interest (South America, Sub-Saharan Africa and rain forest areas in Asia) was identified and mapped.
The forest cover was extracted by masking out all pixels without any forest data or no forest loss data. Then each pixel was mapped on to a set of png map tiles.
The png tiles have a size of 256x256 pixels. Each pixel contains three channels (RGB) where we mapped the forest data.
- R (Red): The red channel contains the values for treeCover (in year 2000) in percent (0 - 100)
- G (Green): The green channel contains a flag for tree loss (0 - 1) (1 = loss, 0 = no loss)
- B (Blue): The blue channel contains the year (if applicable) when the forest loss occured (two digit, ie. 2017 = 17)
This method allows us to produce a map that contains all forest data compressed into a single png tile, reducing load time.
The forest data created does not contain data on forest that has grown back.
The reasoning for this is that although forest growth can be, visible in parts of the Sumatra islands, the extent of forest growth in the areas that this map covers are small enough to ignore for this specific implementation of the data.
(Hansen, M. C., P. V. Potapov, R. Moore, M. Hancher, S. A. Turubanova, A. Tyukavina, D. Thau, S. V. Stehman, S. J. Goetz, T. R. Loveland, A. Kommareddy, A. Egorov, L. Chini, C. O. Justice, and J. R. G. Townshend. 2013. “High-Resolution Global Maps of 21st-Century Forest Cover Change.” Science 342 (15 November): 850–53.)