National Geologic Map Database
GeMS on GitHub GeMS Documentation GeMS on Gitter

In 2014-2017, this database design was extensively reviewed and test-implemented by the U.S. Geological Survey and the State Geological Surveys. During this process, certain modifications and clarifications were made to the now-superceded version, NCGMP09v1.1. The current version was formally published by the USGS in September of 2020 and given a new, more pronounceable name — "GeMS" (Geologic Map Schema). Questions or comments may be directed here.

Documentation and Tools
  • Download the PDF — "A Standard Format for the Digital Publication of Geologic Maps, USGS Techniques and Methods 11-B10" is the latest version of GeMS (see Archive for older versions).
  • HTML version of the documentation — prepared by Megan James, South Carolina Geological Survey.
GeMS Toolbox

Delivery Symbology
Standard ArcGIS styles
  • ArcGIS Pro style implementation of FGDC Standard — Comprehensive and authoritative implementation of the standard created by the South Carolina Geological Survey for the NGMDB.
  • AK GeMS symbology — ArcMap style file and report from the Alaska Division of Geological & Geopysical Surveys. Contains the majority of symbols in the standard.
Fonts (required for style files)
  • FGDCGeoAge.otf — OpenType version of special geologic age characters.
  • FGDCGeoSym — five TrueType font files of geologic marker symbols used for decorating line symbols and symbolizing points. These are required for the style files above.
Example databases GeoMaterials vocabulary
  • GeoMaterials — terms and definitions from Appendix 1 of the GeMS documentation, in spreadsheet form.
  • Guidance on datums — what datum(s) should be used for our geologic map GIS databases?
  • AK GeMS Data Dictionary — a description of the Alaska geologic mapping schema. Alaska Division of Geological & Geophysical Surveys.
  • AZGS Geomapmaker — GitHub repository for an ArcGIS Pro ribbon tab/toolbar to help create GeMS-compliant data during the digitization process. Arizona State Geological Survey.
  • MapMerger — GitHub repository for a tool for merging GeMS map databases. Ryan Crow, USGS.
  • Monthly Collaborative Database Effort for Geology (CDEFG) meetings on the development of a multi-map, multi-user database based on GeMS at the Alaska Division of Geological and Geophysical Surveys. Many general GeMS topics discussed in addition to building an enterprise database.
  • Workflows, tools, and documentation for working with GeMS databases by the Wisconsin Geological & Natural History Survey.
  • FGDCcmyk — ArcMap and ArcGIS Pro style files containing only the polygon fill colors shown in the FGDC CMYK Color Chart. Also known as wpgcmyk.style and derived from the ArcINFO shadeset wpgcmyk.shd.
  • FGDC_GSC_20100414 — ArcMap and ArcGIS Pro style files of the Canadian Geological Survey's partial implementation of FGDC symbols; mostly point, line, and text symbols. Requires installation of the FGDCGeoSym font files described above.
  • GSC_FGDC_GeologicMapSymbols — ArcMap and ArcGIS Pro style files containing both FGDCcymk and FGDC_GSC_20100414 symbols. Requires installation of the FGDCGeoSym font files described above.

Get help

  • If your project or agency has tools, workflows, or documentation you would like to share, please consider having links posted here. Write to gems@usgs.gov to discuss.
  • Development of the python scripts in the geoprocessing toolboxes is handled through GitHub. If you would like to offer changes or enhancements, the best way is through the GitHub flow but you can also send files and/or documentation for the tools and they will be considered for incorporation.
  • If you find a bug in a toolbox tool or would like to request an enhancement, please submit an issue at the appropriate repository (see Documentation and Tools).
  • For informal discussion of all aspects of using the schema, you can join the Gitter chat room or send an email to request to join the Digital Mapping Techniques community listserv.


GeMS ("Geologic Map Schema", formerly "NCGMP09") is the standard schema for geologic map publications funded by the U.S. Geological Survey's National Cooperative Geologic Mapping Program (NCGMP). Its design specifies encoding the content analogous to that contained in a traditional geologic map published by the USGS and by State Geological Surveys. Implementation in ESRI software is described in GeMS, in order to adhere to USGS policy and because this is the GIS most commonly used in the USGS, in the State Geological Surveys, and in the larger community.

This schema is an outcome of nearly two decades of work among numerous individuals and projects, in the NCGMP and in other programs and in many agencies. In particular, during this period the National Geologic Map Database project (NGMDB) has been charged under the Geologic Mapping Act to support the development of geologic map standards and guidelines. Throughout this time, it has been clear that there is no single "right" approach, database needs vary from project to project, and these needs may contrast markedly with the long-term requirements for the national database. This schema, as noted, is intended to address the needs of geologic mapping projects particularly for data delivery, and so we sought consensus on a design that met those needs.

NCGMP09 was introduced at the Digital Mapping Techniques '09 meeting (May, 2009), as version 0.8.2, in order to solicit preliminary comments and testing. Version 1.0 was released October 14, 2009, for presentation at the Geological Society of America's Annual Meeting. In the months following, more extensive evaluations were received, and in response the design evolved. A revised version was published in the DMT'09 Proceedings as NCGMP09 (version 1.1). During that timeframe, NCGMP09 development was supported by the USGS/AASG National Geologic Map Database Project and the USGS Pacific Northwest Geologic Mapping Project (Ralph Haugerud, Stephen Richard, David Soller, and Evan Thoms). Since then, implementation and potential revisions or enhancements to NCGMP09 have been conducted by a wider group of colleagues (see Progress Report of Sept. 25, 2013). In 2014-2017, the schema and documentation were extensively reviewed and test-implemented by the U.S. Geological Survey and the State Geological Surveys. During this process, the need for certain modifications and clarifications, including renaming the schema to GeMS, was identified and in 2018, a draft of a new peer-reviewed, but still provisional, release was made available. This was formally published on September 2, 2020 by the USGS as a Techniques and Methods series report (number 11-B10) and is now the documentation for the current release of GeMS.

Regarding availability and maintenance of this database design, under the authority of the Geologic Mapping Act of 1992 (and subsequent reauthorizations), the National Geologic Map Database project will function on behalf of the NCGMP as coordinator of database design changes and maintenance. This activity will be conducted in cooperation with NCGMP projects and other identified stakeholders (e.g., the Association of American State Geologists). Long-terms plans include proposing GeMS as the standard supported by the Federal Geographic Data Committee. Please note that the schema and documentation, and the software tools that support it will evolve over time, in response to the needs of users and geologic mappers, and to advances in technology.

Archive of previous versions and related information

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