Information about the PA DEP longwall panel coal mine data
(From the accompanying metadata)

Abstract:
Coal mining has occurred in Pennsylvania for over a century. A method of coal mining known as Longwall Mining has become more prevalent in recent decades. Longwall mining involves cutting the coal off the face of a long wall panel of coal in a single pass of the machinery. The machinery will then advance forward and perform another pass along the coal face. The broken off coal is hauled to the surface using conveyor belts. As the machinery advances forward intot eh coal panel, the mine roof is allowed to collapse behind it. This dataset identifies the footprint of these longwall panels relative to the surface.

Purpose:
The purpose of this dataset is to identify the footprint of longwall panels relative to the surface.

Usage:
Not for commercial use of resale. The User shall save the Commonwealth harmless from any suits, claims or actions arising out of the use fo the data files or accompanying documentation, or arising out of any defect in the data files or accompanying documentation. The Commonwealth excludes any and all implied warranties and makes no warranty or representation with respect to the data files or accompanying documentation, including quality, performance, merchantability, or fitness for a particular purpose. These data files and documentation are provided AS IS and the User assumes the entire risk as to their quality and performance. Those parties involved with the development and distribution of this data will not be liable for any direct, indirect, special, incidental, or consequential damages arising out of the use or inability to use the FILES or any accompanying documentation.

Description:
This dataset was created from digitizing mine maps developed from multiple mine operators. Credit should be given to the mine operators for developing the original mine maps. This dataset was created by scanning mine maps submitted to the Pennsylvania Department of Environmental Protection (DEP) as part of the Application for Bituminous Underground Mine or part of a six month mine map update required under the permit. Various scanners were used at different locations at different times. Once a map was scanned, most of the electronic images were post-processed using Adobe Photoshop CSx, to computers to display them efficiently. Some of the processes performed on the images include grayscaling, image size reduction, cropping, and auto contrasting. Once the images were a manageable size, they were georeferenced using ArcGIS to base maps, including but not limited to 7.5 minute USGS topographic maps and PAMAP aerial photography. Next, the longwall panel footprints on the map image were digitized and attributed.

Attribute Accuracy:
Several attributes contain details of mine names, operators, status, and other details of mining operation. These mine names, operators, status, and other details of mining operations change over time and there is NO guarantee that the data listed is the most accurate, recent, and/or complete.

Horizontal Positional Accuracy:
This dataset was created by digitizing georeferenced mine maps of various/unknown accuracy and various/unknown coordinate systems to various base maps, including but not limited to USGS topographic maps and PAMAP aerial photography. Therefore horizontal accuracy of the polygons representing the longwall panel footprints are UNKNOWN.