COMPILING A GIS-BASED GEOLOGIC MAP FROM MULTIPLE LEGACY FORMATTED DATA SOURCES

Constructing a GIS from preexisting, legacy-formatted maps can be an unfamiliar and arduous task for many geoscientists. To address this issue, we describe an approach for compiling different legacy map formats into a single GIS-format geologic map. Our new map encompasses adjacent areas within the northern Appalachian fold-thrust belt of eastern New York State: the Kingston orocline (published, paper format) and the historic Rosendale natural cement region (unpublished, Adobe Illustrator format). The new map compilation was constructed in ESRI’s ArcGIS software using a method developed by Susan Priest (USGS), which outlines the creation of feature classes necessary for compiling typical geologic map data. Our approach for working with paper maps began by creating a scan of the original Kingston map, which was then georeferenced in ArcGIS so that map data (e.g., contacts, attitudes, fold axes) could be digitized from the computer screen. During this phase, we evaluated various digitizing tools for accuracy, ease of use, and affordability, including a FingerSystem iPen (simple, affordable, but inaccurate), the Adapx Capturx system (simple and accurate, but time consuming and expensive), a Wacom Cintiq 21UX tablet (extremely simple and accurate, but very expensive), and a standard desktop optical mouse. While we preferred working with the Cintiq tablet, the majority of data were digitized using an optical mouse. We applied a different approach for the Adobe Illustrator-based Rosendale map. Data were first georeferenced in Illustrator using Avenza System’s MAPublisher plug-in, which transforms the vector-based polygons and lines in Illustrator drawings to map data associated with a location, scale, and map projection. These data were then exported as shapefiles and imported directly into ArcGIS. As with the Kingston map, bedding attitudes from the Rosendale map were digitized from the computer screen. Shapefiles generated through this process can also be imported into Landmark’s LithoTect software where they can be combined with georeferenced DEM data and exported images of the geologic map. LithoTect’s user-friendly interface can then be used to quickly digitize bedding attitudes that can be used to project geologic relationships into cross-sectional profiles for additional analyses (e.g., balancing).