Southern Terra Cognita

Discrete Global Grids


These pages provide resources for a new class of data structures for geospatial applications, which we call "Discrete Global Grids" (DGGs). In particular these pages contain information on DGGs developed using the Icosahedral Snyder Equal Area (ISEA) projection.

These pages are created and maintained by Kevin Sahr of the Department of Computer Science at Southern Oregon University. The information in these pages is based on the work of an extended community of DGG researchers. Please send Kevin an email if you have questions about our research, information to add, or if you would like to be informed when these pages are updated.

The following resources are currently available:


This research was sponsored in part by the environmental statistics research project conducted as part of the Environmental Monitoring and Assessment Program (EMAP). EMAP is a research effort of the United States Environmental Protection Agency directed at improving monitoring and assessment methodology. Although the research is conducted wholly or in part by the U.S. Environmental Protection Agency under cooperative agreement CR821672 with Oregon State University and under contract 1B0250NATA, it has not been subjected to the Agency's peer and administrative review, and hence does not necessarily reflect the views of the Agency.

Additional funding has been provided by the Biodiversity Research Consortium under cooperative agreement PNW-92-0283 with the USDA Forest Service.