Issue link: http://read.dmtmag.com/i/55888
providing results in a standard geodatabase for all geologic map projects and allowing more-streamlined updates to the OGDC database for future releases. Data Creation Figure 2. FGDC Standard is a highly recommended reference guide to geologic features and cartographic symbology. the cartographic representations developed by Esri. The resulting database design is shown in Figure 3. It employs 95 domains, 13 relationships, 16 tables and 21 feature classes. After creating the custom geodatabase, DOGAMI migrated the 2009 OGDC database to the new for- mat in 2011. The four Shapefiles were imported into existing feature classes, and the tables within the Access database were converted to geodatabase domain tables or standalone tables in the geodata- base. The relationships also were duplicated in the file geodatabase. Topology rules also were created and implemented in the new file geodatabase, allowing for easier QA/QC of the features and streamlined error checking during the data-creation process. The file geodatabase format now is used for all new DOGAMI geologic map projects, As noted earlier, the data-creation process used by DOGAMI geologists was neither streamlined nor stan- dardized. This resulted in a difficult map-production process at the end of a long mapping project, and flawed data proliferated, including polygon gaps and slivers as well as overlapping polygons. In addition, contact lines, recommended by USGS as a data- feature class, weren't being created. (Contacts are lines representing the location where rocks form contiguous sections of Earth's crust or, in GIS terms, outlines of the primary geologic unit polygons shown on the map.) To solve this problem, DOGAMI geologists were trained on the use of Esri's editing and topology tools. Then the data-creation methodology was changed so contact lines are created first, and tools from Esri's ArcToolbox are used to create the polygons. This process allows for quick and efficient QA/QC of the data throughout the data-creation cycle as well as creation of topologically correct contact lines and map-unit polygons. The geologists use LIDAR raster derivatives to cre- ate contact lines at a 1:8,000 scale and are restricted not to a single quadrangle but rather to the extent of the LIDAR data for the area being mapped. Data attribution using the built-in domains also makes this element of the process more efficient and prevents typographical errors from being introduced into the database. Finally, the attribution process integrates USGS feature codes defined in the FGDC Digital Cartographic Standard for Geologic Map Symbolization to aid in map production. Cartographic Representations The underlying principle and benefit of the Esri Geologic Mapping Template is use of the USGS codes in the FGDC Digital Cartographic Standard for Geologic Map Symbolization. Each feature in the database is attrib- uted with a code from the FGDC Standard that matches a specific symbol and description (e.g., 1.1.1 Contact: identity and existence certain, location accurate; 2.2.1 Normal Fault: identity and existence certain, location accurate; Ball and bar on downthrown block). Because the geodatabase design follows the USGS/ Figure 3. The current OGDC database design/schema depicts the custom file geodatabase currently used at DOGAMI on all geologic mapping projects. 20 GEO W ORLD / FEB R UA R Y 2O12 Esri template, DOGAMI cartographers can rely on the attributes created by geologists to dictate the symbol- ogy shown on the map. Therefore, cartographers don't Geologic Mapping