The 5-degree latitude/longitude grids contained in this dataset make up the longest continuous set of daily gridded Northern Hemisphere sea-level pressure data in the DSS archive. These grids have been assembled by DSS from the grids of various meteorological chart digitization projects and operational analyses. Grids begin in 1899 and cover the Northern Hemisphere from 15N to the North Pole. The dataset continues to be updated regularly as new data become available.

In the earlier years, there is one grid per day, but from July 1962 on, there are two grids per day. Prior to 1946, the original grids had a 10-degree resolution and the intermediate points were interpolated and indicated as such. Also in this period, there are times when large numbers of gridpoints are missing, particularly over the Asian continent. For more information, see the documentation about original data points.