Digital Mapping Resources
Below are descriptions and links to recommended sources of digital data that reside outside of the Pennsylvania Geological Survey’s website. On these outside websites, you can find georeferenced map images, orthoimagery, and vector data that are used in the production of geologic maps. There are also links to standards and software that will assist you in using GIS data and creating geologic maps.
Georeferenced map data and images for Pennsylvania can be obtained through the Pennsylvania Spatial Data Access (PASDA) website. PASDA, which was developed and is maintained by the Pennsylvania State University, is the official public access source of geospatial information for the commonwealth. Among its wealth of resources are PAMAP lidar data and orthoimagery, georeferenced topographic maps, and vector data for roads, physiographic regions, political and geographic boundaries, and streams and rivers.
The Pennsylvania Department of Conservation and Natural Resources has a PAMAP Data Download page that is an easy interactive way to obtain PAMAP data from the PASDA site.
The NGMDB, a product of the U.S. Geological Survey (USGS) and the Association of American State Geologists (AASG), is a centralized listing of geologic maps and any associated GIS datasets for the United States of America. The “Map Catalog” on this site provides a useful search tool for hundreds of Pennsylvania Geological Survey publications that include geologic maps.
The guide FGDC Digital Cartographic Standard for Geologic Map Symbolization is a national standard for symbolizing lines, points, and polygons shown on geologic maps. It provides for a uniform appearance of geologic maps and is expected to be followed on maps submitted to the NGMDB (see above). The standard was written by the Geologic Data Subcommittee (GDS) of the Federal Geographic Data Committee (FGDC) and prepared by the U.S. Geological Survey (USGS). It was published in August 2006 and revised several times since.
An ArcGIS template for the standard was developed by the USGS, Esri, and the Arizona Geological Survey. It is available from this website: http://www.arcgis.com/home/item.html?id=bb02aa75305f40ff87fb6106aa297da9
Part of the standard provides guidelines for geologic symbols. In order to create the symbols properly, one needs to use the FGDCGeoAge font. Font files and instructions are included in the download.
Georeferenced images of U.S. Geological Survey (USGS) topographic maps in the form of GeoPDFs can be downloaded for free from the USGS store through the “Map Locator & Downloader” link. There are thousands of Pennsylvania maps available from this website, which includes images from the 7.5-minute, 15-minute, 30- x 60-minute, and 1- x 2-degree topographic map series. Many of these older maps are no longer in circulation, but those that are still available in printed form can be purchased through the website.
In addition to the historical topographic maps, the website includes 7.5-minute topographic maps that were produced digitally. These maps are referred to as US Topo, and in addition to the standard topographic map elements (hydrography, topographic contours, roads, and so on), they include an orthoimage of the quadrangle. The elements in the US Topo maps are layered, allowing the user to turn visibility on or off as desired. The maps are produced by the National Geospatial Program of the USGS and are described at http://nationalmap.gov/ustopo.
Free software that allows you to view and explore GIS data can be obtained from the Esri website. With ArcGIS Explorer Desktop and Explorer for ArcGIS, you can access ArcGIS Online base maps and layers, merge them with your own data, and perform spatial analysis.