DESIGN AND IMPLEMENTATION OF A NADM COMPLIANT DATA MODEL FOR REGIONAL TO OUTCROP SCALE GEOLOGIC MAPPING PROJECTS

Since 2000, NSF-funded undergraduate researchers in Casco Bay, Maine have collected a significant amount of geologic field data, digital outcrop survey data, accompanying field photographs, pertinent preexisting maps and available aerial imagery. Each year's project involves a multiple-user digital work space that averages 20-40GB in size with over 10,000 files generated during field survey, data processing and GIS compilation. Organizing and storing six years worth of project data in an efficient, scalable, and standardized data structure that functions in the field as well as in the laboratory has been a recurring problem throughout this period. This difficulty is common in state-level geologic surveys and in other areas of field research (National Research Council, 2006). The solution developed is derived from the U.S. Geological Survey's North American Geologic Map Data Model (NADM). NADM represents geologic data at varying scales and conforms to Open Geospatial Consortium (OGC) standards. These standards make data interoperable thus supporting dissemination and further research. The model arranges data in three discrete but inter-related sections: Geologic Concept, Metadata, and Geologic Representation. Geologic Concept is the actual phenomena that the data represents, Metadata concerns the information about that data, and Geologic Representation is a set of definition standards (ontologies). To date there has been some success using this structure within the personal geodatabases available through ArcGIS, however, size limitations quickly become a problem. ESRI's new geodatabase format, the file geodatabase, offers some potential for overcoming this problem. In this form, data are stored in binary files that do not have the same space limitations, are not limited by resolution requirements, and are available across various computing platforms. When used in the field, the process requires that metadata for all survey instrument files be collected on preprinted cards or entered directly into field computers and transferred to the developing database. This process formats the metadata so that it can be queried and updated as mapping continues. At present, this solution is well suited to any high-resolution digital field mapping environment. Later, a customized open-source solution could be adapted to handle these large geologic database projects.