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Structure contours for the Upper Freeport coal bed in Maryland, Ohio, Pennsylvania. and West Virginia

Frequently-anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

What does this data set describe?

1. How should this data set be cited?

   Calef, Fred J. III, 19990415, Structure contours for the Upper Freeport coal bed in Maryland, Ohio, Pennsylvania. and West Virginia:.

   This is part of the following larger work.

   Northern and Central Appalachian Basin Coal Regions Assessment Team, 2000, 2000 Resource Assessment of Selected Coal Beds and Zones in the Northern and Central Appalachian Basin Coal Regions: U.S. Geological Survey Professional Paper PP1625-C, U.S. Geological Survey, Reston, VA.

   Online Links:

   • <http://pubs.usgs.gov/prof/p1625c/>

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -82.701

   East_Bounding_Coordinate: -78.193

   North_Bounding_Coordinate: 41.354

   South_Bounding_Coordinate: 38.406

3. What does it look like?

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: 1970

   Ending_Date: 1997

   Currentness_Reference: data collection and collation period

5. What is the general form of this data set?

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

      This is a Vector data set. It contains the following vector data types (SDTS terminology):

      • GT-polygon composed of chains (6346)

   2. What coordinate system is used to represent geographic features?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.00001. Longitudes are given to the nearest 0.00001. Latitude and longitude values are specified in decimal degrees.

      The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.4.
      The flattening of the ellipsoid used is 1/294.98.
      

7. How does the data set describe geographic features?

   c9011st.pat

   polygon attribute table for coverage (Source: ARC/INFO)

   elev_st

   average elevation value of bounding structure contour lines. NOTE: values of -9999 are assigned to eroded areas within the coal bed extent. (Source: this study)

   Range of values
   Minimum:	-500
   Maximum:	3900

   c9011st.aat

   arc attribute table for coverage (Source: ARC/INFO)

   elev_st

   elevation value of contour lines. NOTE: values of -9999 are assigned to outcrop, which was used as a clipping polygon and are not true elevation values. (Source: ARC/INFO)

   Range of values
   Minimum:	-400
   Maximum:	3800

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Fred J. Calef III

2. Who also contributed to the data set?

   The stratigraphic data stored in the National Coal Resources Data System (NCRDS) were submitted since the middle 1970's through State cooperative programs. The data for the Upper Freeport coal bed was used with the permission and through the cooperation of coal geologists (primary contacts listed) at the West Virginia Geological and Economic Survey (Mitch Blake), the Pennsylvania Bureau of Topographic and Geologic Survey (James R. Shaulis and Viktoras W. Skema), the Ohio Division of Geological Survey (Richard W. Carlton) and the Maryland Geological Survey (Dave Brezinski). [WVGES, PAGS, OHGS, and MDGS, respectively.] It is recommended that new data be obtained from the State geological surveys that are the original sources of the information in this study.

3. To whom should users address questions about the data?
   Susan J. Tewalt
   U.S. Geological Survey, Eastern Energy Resources Team
   MS 956 National Center
   Reston, Virginia 20192
   USA
   

   703-648-6437 (voice)
   

Why was the data set created?

The purpose of Professional Paper 1625 is to release the interpretation of assessment and modeling data for the the top-producing coal beds in the northern and central Appalachian Basin coal regions. This dataset was used in the National Coal Resource Assessment Program to produce a structure map, which was used to calculate overburden thickness in the evaluation of resources for the Upper Freeport coal bed in Region 9, the Appalachian basin. The dataset is useful for regional studies - not applicable to local scales.

How was the data set created?

1. From what previous works were the data drawn?

2. How were the data generated, processed, and modified?

   Date: 1998 (process 1 of 8)

   Upper Freeport Coal data from NCRDS was downloaded to StratiFact. Elevation on top of the Upper Freeport was searched from the database and was subsequently exported to ARC/INFO and into a point coverage.

   Date: 1998 (process 2 of 8)

   Lower Freeport and Lower Kittanning coal bed structure information was used in Armstrong, Cambria, Clarion, Elk, Indiana, Jefferson, and Westmoreland counties in Pennsylvania and interpreted (elevation increased) to the approximate Upper Freeport coal bed structure. Lower Freeport coal structure contours were raised 50 feet in elevation. Lower Kittanning coal structure contours were raised 200 feet in elevation. Source of Lower Kittanning and Lower Freeport data was the Pennsylvania Bureau of Topographic and Geologic Survey, Mineral Resource Report #92, Part 1, 1987. These data were digitized, edited, and appended from a paper source based on USGS 7.5-minute quad sheets.

   Date: 1999 (process 3 of 8)

   Insufficient computer memory necessitated intersecting the digitized lines and points with four overlapping quadrants that covered the extent of the Upper Freeport bed. This created the need to perform the following topogrid step for each of the four areas (labeled se, sw, nw, ne).

   Date: 1999 (process 4 of 8)

   Gridding of 12,945 elevations (ARC/INFO 7.2.1 GRID) with a limited number of anomalous data points removed to better reflect local structure. Final grid parameters used: TOPOGRID command utilizing the ANUDEM algorithm (uses a combination of inverse distance weighting, kriging, and spline-method like algorithms), 100 meter cell size, extrapolation over specified x,y extent. Average Z-error is unknown, though expected to be within 100 feet (half contour interval). Both digitized arcs from paper sources and points from the database were input to topogrid command for each quadrant.

   Date: 1999 (process 5 of 8)

   The four quadrant grids created with topogrid were mosaiced together.

   Date: 1999 (process 6 of 8)

   Mosaiced grid was contoured with a 200-foot interval using LATTICECONTOUR and made into an ARC/INFO line coverage representing Upper Freeport structure contours.

   Date: 1999 (process 7 of 8)

   Structure contours were converted into structure polygons using the convert-ism.aml program. This program created polygon labels with a value half way between the contour intervals on either side of the polygon. A decision was made to leave small contour polygons in the resulting file and not to subjectively remove them, even though they may be artificial.

   Date: 1999 (process 8 of 8)

   Structure coverage was projected into digital degrees using the PROJECT command into GEOGRAPHIC projection, NAD27 datum, and digital degree units.

3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

1. How well have the observations been checked?

   Deductive_Estimate: The range of elevation values in the well-point source information was -500 to 3940 feet. The range of elevation values in the digitized structure-line source was 100 to 3700 feet. The resultant range of the gridded surface was -526 to 3950 feet; extrapolation was used over the x,y extent. The average absolute Z-error of the grid is unknown.

2. How accurate are the geographic locations?

   A wide variety of data sources were used as input to this data set. The worst horizontal error is expected to be approximately 1/4 mile. Original data were stored in NCRDS in latitude/longitude coordinates with a possible precision of decimal seconds. Some loss of precision was made upon conversion to StratiFact. Location coordinates were converted to Albers Equal Area projection (.01 meter precision) prior to gridding in ARC/INFO.

3. How accurate are the heights or depths?

   The raw input data represent values of the elevation above MSL of the top of the Upper Freeport Coal for each borehole or point of measurement. The original measurement errors associated with the topographic surface elevation are unknown; no verification of surface elevations at points of measurement was made with any paper or digital reference. In addition, in Armstrong, Cambria, Clarion, Elk, Indiana, Jefferson, and Westmoreland counties of Pennsylvania, the Lower Freeport and Lower Kittanning coal bed structure information was used to approximate Upper Freeport coal bed structure in areas where Upper Freeport coal bed structure data was absent or insufficient for direct interpretation. Lower Freeport coal structure contours were raised 50 feet in elevation. Lower Kittanning coal structure contours were raised 200 feet in elevation. The vertical accuracy is estimated to be equivalent to 100 feet (half of one contour interval).

4. Where are the gaps in the data? What is missing?

   Input points were irregularly distributed over the spatial extent of the study, therefore areas of sparse data will not reflect ground truth. There is a point coverage available (c9011dp) that contains most publicly available point elevations used to create this map. The Upper Freeport coal was selected by name from the stratigraphic data base stored in StratiFact, a relational data base manager in use by the USGS National Coal Assessment. In some areas with no point data, the Upper Freeport coal bed elevation was extrapolated from structure contour maps of other adjoining coal beds.

5. How consistent are the relationships among the observations, including topology?

   Topologically clean

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints: none

Use_Constraints: to be used for regional analysis only

1. Who distributes the data set? (Distributor 1 of 1)
   Susan J. Tewalt
   U.S. Geological Survey, Eastern Energy Resources Team
   MS 956 National Center
   Reston, Virginia 20192
   USA
   

   703-648-6437 (voice)
   

2. What's the catalog number I need to order this data set?

   USGS Professional Paper 1625-C: Chapter D, C9011ST.E00

3. What legal disclaimers am I supposed to read?

   Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although these data have been used by the U.S. Geological Survey (USGS), no warranty, expressed or implied, is made by the USGS as to the accuracy of the data and related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the USGS in the use of these data, software, or related materials.

4. How can I download or order the data?
   • Availability in digital form:

     Data format:	polygons of coal elevation in format ArcInfo export (version 7.2.1) Size: 11.7 megabytes
     Network links:	<http://pubs.usgs.gov/prof/p1625c/CHAPTER_D/ChapDstructure.zip>

   • Cost to order the data: none

Who wrote the metadata?

Dates:

Last modified: 15-Apr-1999

Metadata author:

Susan J. Tewalt
U.S. Geological Survey, Eastern Energy Resources Team
MS 956 National Center
Reston, Virginia 20192
USA

703-648-6437 (voice)

Metadata standard:

Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)