Digital Geologic Map Data Models
Currently many groups are working on geologic map data model design. One of the best known of these to date is the Geological Survey of Canada, U.S. Geological Survey and Association of American State Geologists effort: NADM Conceptual Model 1.0— A Conceptual Model for Geologic Map Information
Technical working groups under the the North American digital geologic map data model Steering Committee have begun to solve some of the thorny issues involved in developing a workable North American Data Model (NADM) for geologic mapping: Specifically science language for earth materials. For more detail and downloadable products go to http://nadm-geo.org/products.html.
The Idaho Geological Survey has been producing geologic maps digitally since 1989. The Idaho Survey began to capture a database of basic geologic attributes associated with each geologic feature on a map in 1992 as part of its map digitizing process. Beginning in 1996 metadata, or information about the map and its sources, has been input for each 30 x 60 minute geologic map compilation. These attributed spatial data can be used in a Geographic Information System (GIS) to perform simple queries or analyses. However, to receive consistent and meaningful answers to complicated questions about the geology on a digital map, requires yet another database of map information derived from the map legend.
Taken together, the spatial map data, map legend, and metadata comprise a digital geologic map database. The design of these data sets and how they relate to one another to supply reasonable interpretations of the map is a digital geologic map data model.
Idaho Survey's Data Model
The Idaho Geological Survey has created a statewide ESRI Geodatabase for storing, managing, and distributing Idaho geologic map data. The model for this design resulted from work done by the Idaho Survey over the past 8 years. The work flow strategy around the implementation of the geodatabase improves the productivity of the survey by capturing map data using existing procedures and automating the migration processing of data tiles into feature classes in the statewide geodatabase.
Geodatabase Design Highlights
The Idaho Statewide Geologic Map Geodatabase (ISGMG) follows the physical design of the Idaho Geologic Map Data Model v3.1 evolved from the earlier Idaho Geologic Model v2.1. Key changes made to 2.1 allow data to be stored in one statewide database. The following are some of the highlight features of the ISGMG:
! The design is composed of four data groupings: Spatial, map unit, earth materials, metadata.
! The design of the database allows for two levels of map object tracking or coding: By 30' x 60' tile or statewide.
! All contacts (poly boundaries) of a particular polygon are linked to the polygon.
! Additions and changes to earth materials section based on work done by the North American Data Model’s Science Language Technical Team (SLTT) have been incorporated into the design (NADM-SLTT, 2004a and 2004b).
! Descriptions from referenced geologic sources can be stored as well as URL links to IGS online PDF maps.
! Map unit history and changes are tracked.
! Object-level attribution including geologic source reference, line type, and feature name.
Freed, J.S. and Stanford, L.R., 2005, Map Production and Data Distribution the Idaho Way: An Update, in Soller, D.R., ed., Digital Mapping Techniques ’05—Workshop Proceedings: U.S. Geological Survey Open-File Report 2005-1428, p. 55-59.
North American Geologic-Map Data Model Science Language Technical Team, 2004a, Report on progress to develop a North American science-language standard for digital geologic-map databases; Appendix B – Classification of metamorphic and other composite-genesis rocks, including hydrothermally altered, impact-metamorphic, mylonitic, and cataclastic rocks, Version 1.0 (12/18/2004), in Soller, D.R., ed., Digital Mapping Techniques ’04—Workshop Proceedings: U.S. Geological Survey Open-File Report 2004-1451, 56 p. Appendix B accessed at http://pubs.usgs.gov/of/2004/1451/sltt/appendixB/.
North American Geologic-Map Data Model Science Language Technical Team, 2004b, Report on progress to develop a North American science-language standard for digital geologic-map databases; Appendix C1 – Sedimentary materials: Science language for their classification, description, and interpretation in digital geologic-map databases; Version 1.0 (12/18/2004), in Soller, D.R., ed., Digital Mapping Techniques ’04—Workshop Proceedings: U.S. Geological Survey Open-File Report 2004-1451, 595 p. Appendix C1 accessed at http://pubs.usgs.gov/of/2004/1451/sltt/appendixC/appendixC_pdf.zip.
Stanford, L.R. and MacKubbin, V.T., 2000, Application of a Digital Geologic Map Data Model in ArcView GIS, in Soller, D.R., ed., Digital Mapping Techniques ’00—Workshop Proceedings: U.S. Geological Survey Open-File Report 00-325, p. 55-56.
To learn more, download the current version of the Idaho Survey's data model documentation: