The FGDC Digital Cartographic Standard for Geologic Map Symbolization, released in 2006, provides guidance and assets for the preparation of geologic maps. It includes a large array of reference styles for geologic linework and map symbology.

This repository contains the FGDC library of 480 map and lithologic patterns extracted to SVG and PNG, for use on the modern web. This can be paired with other collections of linework and geologic symbols for the construction of slick geologic maps and stratigraphic columns.

Credits and change history

• Created by Daven Quinn on July 15, 2017
• Fixes by Kelsey Ciarrocca (USGS) integrated on August 10, 2017
• Valuable input and guidance from Chris Garrity, Taryn Lindquist, and David Soller (USGS)
• CC0 public domain dedication added on May 24, 2019
• Improvements to documentation on December 18, 2019

The FGDC manual is a work of thoughtful cartographic design, and the symbology is unmatched in quality and breadth. Patterns are available as .eps and .pdf files, and a subset is packaged as an ESRI ArcGIS *.style. However, the original formats are tied to the Adobe and ESRI ecosystems and, increasingly, dated – recent versions of Adobe Illustrator CC have difficulty importing pattern swatches from the files provided on the FGDC site.

Here, the patterns are repackaged into modern formats which can be used on the web, dependably read in virtually all GIS and graphics software, and flexibly incorporated into derived products for specific tasks. Along these lines, this package includes a catalog of brushes for the iPad drawing app Procreate, which supports the sketching of geologic maps and stratigraphic columns.

This repository includes the complete set of FGDC fill patterns, usable within modern web standards. The SVG files are lossless vectors preserving the full fidelity of the original patterns, and the PNGs are rasterized versions that sacrifice some fidelity for flexibility and ease of use. Paletted PNGs, with lower fidelity and file size, are also provided.

SVGs are a lot more rendering work for the browser. Thus, the png versions of these symbols are recommended for most uses. For some uses, it may be desirable to downsample the images somewhat as well.

Images are addressable with the id (shown in bold beneath each symbol below). For instance, 102-DO.png or 102-DO.svg would work. These patterns form seamless repeating backgrounds using CSS (both within HTML and SVG):

div.sandstone {
      background: url('assets/png/102-DO.png');
      background-size: 100px 100px;
    }

In the future, a CSS stylesheet and/or Javascript API may be added to quickly access the symbols based on common lithology names.

Procreate brushes

This product has been processed into a set of brushes for the iPad drawing program Procreate, enabling the drawing of symbology into stratigraphic columns and maps. These brushes can be individually imported into Procreate and used from the Imported Brushes panel. Some limitations:

• The pixel dimensions of the pattern stamp can only be changed by modifying the brush, using the Zoom and Scale settings in the Grain panel of the brush properties window.
• The brushes can only be generated on MacOS, due to the platform-specific plutil executable.

• The FGDC standards, of course!
• Ryan Clark’s geocarto, which implements a subset of the FGDC standard focused on linework symbols for CartoCSS and Mapnik
• Geologic symbols for QGIS from Ryan Mikulovsky.
• Planetary geology FGDC symbols from Andrea Nass and Alessandro Frigeri
• Taconic Musings’ exploration of geologic mapping in QGIS
• UI icon sets such as Font Awesome

There is some overlap between this project and other distillations shown above, but most prior compilations are focused on linework symbols. It could be useful to bring some of these under the same umbrella for simplicity, or have a separate parallel repository that is the canonical source of linework symbology.

I would like to use this repository as the centerpiece of an authoritative collection of resources for geologic symbology. This could mean several things:

• Add aliases to commonly used lithologic patterns
• Add a mechanism for dealing with FGDC colors
• Incorporate the linework and point symbology part of the FGDC standards
• Add derived products that can speed adoption of styles on multiple platforms
  • QGIS styles
  • CSS stylesheet
  • SVG pattern objects
  • CartoCSS styles

The FGDC standard is comprehensive, but if there is community interest, other symbology could be incorporated into the set.