This week, we are highlighting the HydroSHED product.
Launched in 2006 by World Wildlife Fund USA, the HydroSHEDS programe seeks to provide open digital data layers in support of global hydro-ecological research and applications.
HydroSHEDS offers comprehensive hydrographic data products, such as watershed borders, river networks, and lakes.
This product is based on the data collected by the Shuttle Radar Topography Mission (SRTM) was an initiative that took place in the year 2000 with the goal of acquiring digital elevation models for the majority of the planet. These data were made available to the general public in the year 2015.
The figure depicts the direction of flow from each cell in the digital elevation model to its neighbor with the steepest downslope. To put it another way, the direction that drainage runs, in this case for Buenos Aires province, Argentina.
In order to have a deeper comprehension of the image, it is important to note that the value 0 has been assigned to the flag for each cell that leads to the ocean. A value of -1 is assigned to each cell that represents the position in an endorheic basin. The drainage direction values match the convention followed by ESRI's flow direction: 1 = East, 2 = Southeast, 4 = South, 8 = Southwest, 16 = West, 32 = Northwest, 64 = North, and 128 = Northeast.
The resolution that is now available is 3 arc seconds; however, https://www.hydrosheds.org/ is working on an incredible 12 meter resolution, for the whole planet!!
Bibliography and useful links:
NOTES: the codes to recreate this image, past and future ones will be available in the last post of each month.
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