Keywords: NGMDB data model application.jpg en Figure 11 Simplified representation of the data model and its application to a typical 2-D geologic map The presence of a geologic unit on the map referred to in the data model as an occurrence of that map unit is described by 1 its bounding contacts and faults whose coordinates are stored as the unit ™s geometry ; and 2 its physical properties which are stored as the unit ™s descriptors http //pubs usgs gov/of/2003/of03-471/soller1/index html The National Geologic Map Database Project Overview and Progress U S Geological Survey Open-File Report 03 “471 David R Soller1 and Thomas M Berg 2003 PD-USGov Data model GIS National Geologic Map Database Project |