Figure above shows blocks with year 2000 tree cover >0% with (red) and without (blue) year 2018 forest loss (Hansen et al., 2013), with sampling grid cell (block) size of: a) 2.5x2.5 km, b) 5x5 km, c) 10x10 km, d) 20x20 km. Gray land areas represent treeless blocks excluded from the analysis. The figure illustrates different stratifications that could be produced to target the land cover class of interest (e.g., 2018 tree cover loss) by using sampling grids of different size blocks.
Global equal area blocks in Geographic coordinates (Lat/Long)
Block properties:
- The blocks have a static number of pixels in the North-South dimension for all latitudes, but an increasing number of pixels in the East-West dimension closer to the poles to maintain equal block area.
- Block boundaries are aligned with the GLAD ARD 0.00025°x0.00025° https://glad.umd.edu/ard/home.
- Four block sizes: 2.5x2.5km (~6.25 km² area), 5x5km (~25 km²), 10x10km (~100 km²) and 20x20km (~400 km²).
- Blocks of each size have near equal area, with the maximum block area difference compared to an equatorial block of 0.07% for 20km blocks, 0.14% for 10 km blocks, 0.27% for 5 km blocks, and 0.55% for 2.5 km blocks.
- Boundaries of blocks of these four sizes are aligned and nested in the North-South dimension, but area not aligned in the East-West dimension due to the changing lengths of the parallels.
- Only blocks within land mass are provided, as defined by GADM version 2.0
Dataset Reference
Tyukavina, A., Stehman, S.V., Pickens, A.H., Potapov, P. & Hansen, M.C. (in review) "Practical global sampling methods for estimating area and map accuracy of land cover and change"
Data Download
Map data are provided in Geographic Coordinates (Lat/Long) using the WGS84 reference system, in two formats: shapefiles and rasterized into 10x10 degree tiles (GeoTIFF format). More details about the data format are available in the Readme file at the link below.
