Gridded or raster data is a spatial data format that consists of a matrix of cells, or pixels, organised into rows and columns where each cell contains a value for each grid point across a two dimensional surface. Gridded data covers an area, whereas station data you may obtain for a particular Bureau station applies only to a single geographic location.
The datasets are available in ARC ASCII format and can be ported into a GIS or similar spatial data visualisation tool. They are not suitable for use in Microsoft Excel or other spreadsheet programs. You can download a sample file containing gridded daily rainfall totals for Australia.
The ARC ASCII gridded data format is a non-proprietary ASCII format that can be directly used in ESRI GIS software packages. The format consists of six lines of header information followed by the actual gridded data values. The header information shows the dimensions of the data, the geographic domain, cell resolution and the code for the 'nodata' value. Data are written row-wise, so that the first data record in a block contains values for the northernmost grid-cells moving from west to east. The last data record in a block contains values for the southernmost grid-cells moving from west to east.
Meteorological data is taken from the national climate database of the Bureau of Meteorology – the Australian Data Archive for Meteorology (ADAM). These data come from observations ranging from ground stations, upper air observations, satellites, ships or buoys. Only quality controlled data are used.
A computer analysis technique then applies a weighted averaging process to the data which generates grid points across Australia. This grid-point analysis technique provides an objective average for each square of the grid and enables useful estimates in data-sparse areas such as central Australia.
Each grid-point represents a square area with sides which range from about 5 kilometres (0.05 degrees) on many of the rainfall and temperature products to 200 kilometres (2 degrees) on the tropical cyclone product. The size of the grids is limited by the density of data across Australia.
Maps are created from gridded data by analysing the grid and assigning contour lines in mapping software packages.
Each dataset comes with complete metadata which outlines the important characteristics of each product.
A datum is a mathematical surface on which a mapping and coordinate system is based. Australia adopted the Geocentric Datum of Australia (GDA94) in January 2000.
Coordinate systems provide a common reference information (coordinates) to uniquely determine the position of a particular place or area on the surface of the earth. There are two common types of coordinate systems: geographic coordinate systems (GCS) and projected coordinate systems (PCS).
A geographic coordinate system (GCS) is a coordinate system that enables a particular location to be identified by a set of latitude and longitude degree units. A projected coordinate system is used to project maps of the earth's spherical surface onto a two-dimensional Cartesian Coordinate Plane; i.e. to create flat maps of a curved surface.
Climate gridded datasets are created using a geographic coordinate system (GCS) on GDA 94 datum. Datasets using GCS coordinates can be used within different projection systems. The Bureau's climate maps are created using the Lambert Conformal Conic projection. This projection portrays the physical shape of Australia more accurately than other projection systems.
The Network Common Data Form (netCDF) was developed by UNIDATA and is an open standard self-describing, machine-independent data format that supports the creation, access, and sharing of array-oriented scientific datasets. It is commonly used in climatology, meteorology and oceanography and GIS applications. A netCDF file contains all of the metadata needed to extract and understand the data in the file.
Detailed information and tools for using and viewing netCDF files can be found at :