GRIDDA: Simple software to mould gridded data to a crooked world

Phillip G. D. Ward, James C. Bennett, David E. Robertson

Research output: Chapter in Book/Report/Conference proceedingConference PaperResearchpeer-review

2 Citations (Scopus)


The availability of gridded climate timeseries data for Australia (e.g. AWAP or SILO) has made the collation and analyses of climate data for hydrological applications easier for researchers and practitioners. At the same time, the Bureau of Meteorology have made freely available the Geofabric ( containing digitised catchment delineations for the Australian continent, substantially reducing the effort required to delineate catchments in GIS. However, aggregating gridded climate data to catchments delineated in GIS is still relatively laborious, and is often performed with specialised proprietary software (e.g. Esri ArcGIS).

We present GRIDDA (GRIDded Data Aggregator), a Windows program that quickly and simply calculates area-averages of gridded climate data for catchments delineated in shapefiles. GRIDDA uses a simple polygon intersection method to aggregate gridded data to catchment shapefiles. The Surveyor's area formula is used to compute the area of the grid cell lying within the catchment polygon. GRIDDA weights data from each grid cell by the fraction of area that falls within the catchment boundary to produce area-averaged data for the region of interest.

GRIDDA produces area-averaged timeseries for catchment areas from gridded climate data. In addition, GRIDDA calculates several seasonal and annual metrics for the catchment area for a given climate variable. It includes visualisation and analytic tools, as well as producing plain text outputs that the user can analyse in other software. The user can specify the time periods and the variables to be analysed, making GRIDDA ideal for studying the effects of historical changes in climate over specified areas. The user requires no specialised knowledge, meaning GRIDDA is particularly well suited for students. Further, while GRIDDA was designed with hydrological applications in mind, it can be easily applied to any other field that requires aggregation of gridded data.
Original languageEnglish
Title of host publicationProceedings of the Hydrology and Water Resources Symposium 2012
Subtitle of host publication19-22 November 2012, Dockside, Cockle Bay, Sydney, NSW, Australia
EditorsSeth Westra
Place of PublicationBarton, ACT
PublisherEngineers Australia
Number of pages8
ISBN (Electronic)9781922107626
Publication statusPublished - 2012
Externally publishedYes
EventHydrology and Water Resources Symposium 2012 - Sydney, Australia
Duration: 19 Nov 201222 Nov 2012
Conference number: 34th


ConferenceHydrology and Water Resources Symposium 2012
Abbreviated titleHWRS 2012
Internet address

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