Spatial coverage is good over most of the globe, particularly for the United States and Europe.
Data gaps are evident over the Amazon rainforest, the Sahara desert, Greenland, and Antarctica. Global precipitation data set P. Jones' Temperature data base for the world S. Nicholson's African precipitation data base, etc. Quality Control of the database included visual inspection of graphs of all station time series, tests for precipitation digitized 6 months out of phase, tests for different stations having identical data, and other tests. Similarly, all major inhomogeneities have been flagged, although no homogeneity corrections were applied. Because of the size of the data base, the NDP is not available on floppy diskette.