Proposal for an ArcGeology Version 1 A Geodatabase Design for Digital Geologic Maps using ArcGIS

This document presents a geodatabase design, proposed as an “ArcGeology Version 1”, for digital geologic maps utilizing ESRI ArcGIS® 9.1 or 9.2 software. The design outlines a specific set of feature datasets and feature classes, together with feature attributes, subtypes and domains, suitable for a variety of geologic maps. In addition to basic geology (lithology, contacts and faults, etc.), the maps may include rock/mineral alteration and other overprints, cross-sections, and explanatory legend-graphics such as descriptive lists of map units and correlation charts, used to supplement columnar legends automatically produced by ArcGIS. Setup files are provided to create a new empty geodatabase and companion map document. The geodatabase design is compatible with field work using ArcPad® 6 or 7. This proposal is demonstrated with a fictitious geologic map, UNRCampus, set on the University of Nevada, Reno campus (Figure 1). This demonstration, as a completed ArcMap document and geodatabase with FGDC-compliant metadata, plus the setup files to create similar databases, is available for download at http://ngmdb.usgs.gov/info/dmt/ docs/AG1b.zip. To better understand this report and geodatabase design, the reader invited to fully explore the UNRCampus demonstration. Throughout this document, proficiency with ArcGIS and geodatabases is presumed. For simplicity and portability, only ArcGIS software is used. To create new maps, at least an ArcEditor-level license is required. INTRODUCTION The following typographic conventions are adopted in this document. Geologic mapping and ArcGIS-related technical terms are italicized on first use, and concepts and practices of particular importance are noted in bold italics. Specific data structures, fields, etc., are shown in roman Title Case, without quotes to avoid clutter. Sans serif font is used for Windows-specific file names and also for ArcGIS tool names; the latter are bolded on every use (optionally followed by a parenthetical comment about the user-interface context in which they can be found). Geologic maps present a complex amalgam of basic topographic facts, verifiable field observations, and subjective interpretations (Bain and Giles, 1997); they are among the most intricate of cartographic products. Widespread automation in geosciences, including the use of geographic information systems (GIS), presents the opportunity to capture geologic knowledge into map-databases. In addition to their cartographic sophistication, such map-databases afford more versatility and analytical capability than is possible with traditional paper maps. Based on ESRI ArcGIS software, this proposal for an “ArcGeology Version 1” (AG1) outlines a simple but flexible system for producing a geologic map-database (GMDB) that serves both cartographic and analytical purposes. Because the geoscience community and ESRI have not yet engaged in a collective process to design such a GMDB structure, which by ESRI convention might then be formally named 60 Digital Mapping Techniques ‘07 Figure 1. Fictitious Geological Map of UNR Campus. “ArcGeology”, in this article our proposal will be referred to only as AG1. Specifically, AG1 comprises an ArcGIS geodatabase data model and companion operational procedures that predominantly address the geospatial features of a GMDB. Other groups (NADMSC, 2004 et seq.) have been active in developing a general conceptual model for geoscience information, originally known as “C1.0”, which might eventually be integrated with AG1. Richard (2003) and Richard and others (2004, 2005) have progressively implemented portions of C1.0 in geodatabases with different structures and techniques than those proposed here. Various geological surveys, projects, and individual geologists have developed GMDB designs for their own purposes. Recently, interest has grown around the GeoSciML notation (Commission for the Management and Application of Geoscience Information, http://www.geosciml. org) as a means of sharing geoscience information in more generality than a GMDB. Harmonization of the various GMDB designs is urgently needed in order to make digital geologic map data more widely accessible and more useful, to non-geologists particularly. Accordingly, AG1 has taken a minimalist approach, focused on the geospatial aspects of the map, with the goal of fostering harmony by: 1) simplifying and generalizing the spatial feature classes using subtypes and domains to support essential description for cartography; and 2) deferring the selection/standardization of extended descriptive attributes to the geologic community, where discussion is already underway. In short, the AG1 proposal is intended to evolve to AG2, AG3, etc. with participation and support of the community. AG1 utilizes ArcMap, ArcCatalog, and their associated tools “out of the box,” avoiding any additional software. In addition, AG1 is immediately functional with ArcPad for field mapping. Our expectation is that geologists will become proficient with ArcGIS and its related software in order to produce high-quality GMDB products. Several known problems with ArcGIS also cause problems in the implementation of AG1; these are discussed in Appendix C. 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