The Harmonized World Soil Database is a 30 arc-second raster database with over 15000 different soil mapping units that combines existing regional and national updates of soil information worldwide (SOTER, ESD, Soil Map of China, ISRIC-WISE) with the information contained within the 1:5 000 000 scale FAO-UNESCO Soil Map of the World (FAO, 1971-1981).
The resulting raster database consists of 21600 rows and 43200 columns, which are linked to harmonized soil property data. The use of a standardized structure allows for the linkage of the attribute data with the raster map to display or query the composition in terms of soil units and the characterization of selected soil parameters (organic Carbon, pH, water storage capacity, soil depth, cation exchange capacity of the soil and the clay fraction, total exchangeable nutrients, lime and gypsum contents, sodium exchange percentage, salinity, textural class and granulometry).
Reliability of the information contained in the database is variable: the parts of the database that still make use of the Soil Map of the World such as North America, Australia, West Africa and South Asia are considered less reliable, while most of the areas covered by SOTER databases are considered to have the highest reliability (Southern Africa, Latin America and the Caribbean, Central and Eastern Europe).
HWSD, version 1.21, can be acessed form the IIASA website. Further expansion and update is foreseen in the framework of the Global Soil Partnership (GSP), notably with the excellent databases held in the USA (Natural Resources Conservation Service US General Soil Map, STATSGO), Canada (Agriculture and AgriFood Canada, The National Soil Database NSDB), and Australia (CSIRO, ACLEP, Natural Heritage Trust and National Land and Water Resources Audit, ASRIS).