Airborne geophysical survey: Southern Piedmont, Virginia

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Metadata:

Identification_Information:
Citation:
Citation_Information:
Originator:
U.S. Geological Survey, Department of Interior and the National Geophysical Data Center, NOAA
Publication_Date: 2012
Title: Airborne geophysical survey: Southern Piedmont, Virginia
Geospatial_Data_Presentation_Form: tabular digital data
Online_Linkage:
Description:
Abstract:
Aeromagnetic data were collected along flight lines by instruments in an aircraft that recorded magnetic-field values and locations. This dataset presents latitude, longitude, altitude, and magnetic-field values.
Purpose:
Aeromagnetic surveys are used for geophysical prospecting. Some variations in magnetic measurements are caused by rocks that contain significant amounts of magnetic minerals (magnetite being the most common). These anomalies reflect variations in the amount and type of magnetic material and the shape and depth of the body of rock. The features and patterns of aeromagnetic anomalies can also be used to delineate details of subsurface geology including the locations of buried faults and the thickness of surficial sedimentary rocks.
Time_Period_of_Content:
Time_Period_Information:
Range_of_Dates/Times:
Beginning_Date: 1980
Ending_Date: 1980
Currentness_Reference: ground condition
Status:
Progress: complete
Maintenance_and_Update_Frequency: none planned
Spatial_Domain:
Bounding_Coordinates:
West_Bounding_Coordinate: -79.00
East_Bounding_Coordinate: -78.00
North_Bounding_Coordinate: 37.00
South_Bounding_Coordinate: 36.75
Data_Set_G-Polygon:
Data_Set_G-Polygon_Outer_G-Ring:
G-Ring:
-79.00 37.00, -78.00 37.00, -78.00 36.75, -79.15 36.75, -79.15 36.88, -79.00 36.88, -79.00 37.00
Keywords:
Theme:
Theme_Keyword_Thesaurus: none
Theme_Keyword: geophysical surveys
Theme_Keyword: aeromagnetic data
Theme_Keyword: airborne surveys
Theme_Keyword: magnetic surveys
Theme_Keyword: residual magnetic field
Theme_Keyword: total field
Theme_Keyword: magnetic
Theme:
Theme_Keyword_Thesaurus: USGS Thesaurus
Theme_Keyword: geophysics
Theme_Keyword: geospatial datasets
Theme_Keyword: magnetic field (earth)
Theme_Keyword: aeromagnetic surveying
Theme_Keyword: field monitoring stations
Place:
Place_Keyword_Thesaurus: none
Place_Keyword: United States
Place_Keyword: Virginia
Place_Keyword: VA
Place_Keyword: Piedmont
Place_Keyword: Southern Virginia
Place:
Place_Keyword_Thesaurus: Common Geographic Areas
Place_Keyword: f51025 = Brunswick
Place_Keyword: f51037 = Charlotte
Place_Keyword: f51083 = Halifax
Place_Keyword: f51111 = Lunenburg
Place_Keyword: f51117 = Mecklenburg
Place_Keyword: f51135 = Nottoway
Place_Keyword: f51143 = Pittsylvania
Access_Constraints: none
Use_Constraints:
none. Acknowledgement of the U.S. Geological Survey and the National Geophysical Data Center would be appreciated in products derived from these data.
Browse_Graphic:
Browse_Graphic_File_Name: Browse_Graphic_File_Description:
Reduced-size image depicting the data, 985 x 470 pixels, 246,232 bytes
Browse_Graphic_File_Type: JPEG
Data_Set_Credit:
These USGS employees contributed to reformatting and archiving these data: Viki Bankey, David Daniels, Carol Finn, Pat Hill, Holly Hindle, Bob Kucks, Vicki Rystrom, Sarah Shearer Cooperating contributors from the National Geophysical Data Center are: Ronald Buhmann, David Dater, Susan McLean, Stewart Racey
Native_Data_Set_Environment:
These data were originally recorded on 9-track magnetic tapes and were transferred to CD-ROM. Data processing took place on an HP workstation and a Dell personal computer running a Windows NT or XP operating system. Data were reformatted using the Geosoft, Inc., Oasis Montaj program.
Cross_Reference:
Citation_Information:
Originator: Virginia Division of Mineral Resources
Publication_Date: 1981
Title: Composite aeromagnetic map southern Piedmont, Virginia
Geospatial_Data_Presentation_Form: map
Series_Information:
Series_Name: Virginia Division of Mineral Resources Open-File Report
Issue_Identification: VADMR R7
Publication_Information:
Publication_Place: Charlottesville, Virginia
Publisher: Virginia Division of Mineral Resources
Other_Citation_Details: map scale 1:250,000
Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
The data in this file have been processed using various formulas and methods that are not usually documented but that represent industry standard practices for airborne data reduction. For example, position is listed as latitude and longitude, but these values were derived from the raw navigation data depending on the system used. (see notes under horizontal accuracy). Line numbers were added to records, and unusable data at flight-line ends were discarded (as aircraft slowed and turned around). Separate recordings were correlated by time and assigned to the correct location. The exact accuracies of these processing steps may not be known. They are discussed in the sections on attribute or positional accuracies.
Logical_Consistency_Report:
The data in this file were collected by a single contractor or group who were responsible for collecting and processing the data. The data from this survey were collected using the same instruments (magnetometers, altimeters, navigational systems) throughout the survey and were collected in a normal length of time with no long delays between survey beginning and end. Survey contracts specified the conditions and specifications under which these data were collected. Standard industry practices of the time were followed in data collection and processing.
Completeness_Report:
Loss of data due to poor transmission, channel dropout, obvious spiking, missing channels, and other obvious errors were replaced with the value -9999.9, such as in the radar and barom channels. Sometimes channels were added and filled with dummy values (-9999.9) to comply with the established format. Some records that had no usable data were deleted. The values in the barometric altimeter (barom) channel are not uniform. The days given in the Julian day (jul_day) channel have been corrected using the flight log book.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Flight Path Recovery Horizontal positions of the survey aircraft used to collect data were determined using aircraft navigational aids such as line-of-sight electronic systems that measure the distances from each of two ground stations to the aircraft.
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
The aircraft vertical position was determined using the navigational positioning equipment on the aircraft, which were radar altimeter and barometric altimeter. Radar altimeters are estimated to have an error of 2-5% of the altitude (Richard Hansen, PRJ, Inc., written communication). Barometric altimeters are quite accurate, but are typically operated in an uncorrected mode. The diurnal variation in air pressure over the course of a flight can produce a 50-100 ft error in the barometric altimeter reading. In addition, pressure microcells create short- period air pressure changes equivalent to about 10 ft. under typical conditions (Richard Hansen, PRJ, Inc., written communication) This data set was collected as a draped survey having an average terrain clearance of 500 ft. Because aircraft, especially airplanes, cannot safely maintain a constant terrain clearance, error in vertical position is introduced.
Lineage:
Process_Step:
Process_Description:
Conversion of measured values to geographic position and magnetic values was performed by the contractor using industry standard practices. Details are found under Horizontal_Position_Accuracy_Report, and Vertical_Position_Accuracy_Report Unless noted, conversion processes were not reported to the USGS. Unpublished products generated by the contractor included magnetic tapes, a map of residual or total field magnetics, and perhaps some written documentation.
Process_Date: 1980
Process_Step:
Process_Description:
USGS reformatting of contractor data to standard format. USGS personnel used the software package Oasis Montaj by Geosoft, Inc., to read in the original contractor's data. Latitude, longitude, altitude, and magnetic values were checked for obvious errors or spikes and values of -9999.9 were given where the value could not be reasonably corrected. Other errors in the data were not corrected. Horizontal positions were converted to latitude and longitude if the original values were UTM meters. Elevations were converted from meters to feet (1 m = 3.2808 ft). Often the digital data did not contain date information and only the month and year flown or just a starting date were stated in the written documentation. In these cases, the first day of the month or the date the survey began was used as the Julian date and added to the digital data. Other information was added that was missing from the data file but was recorded elsewhere. The reformatted data were written in the format described in the section on Digital_Transfer_Information.
Process_Date: 20010829
Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: point
Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Geographic:
Latitude_Resolution: 0.0001
Longitude_Resolution: 0.0001
Geographic_Coordinate_Units: decimal degrees
Geodetic_Model:
Horizontal_Datum_Name: North American Datum of 1927
Ellipsoid_Name: Clarke 1866
Semi-major_Axis: 6,378,206.4
Denominator_of_Flattening_Ratio: 294.98
Vertical_Coordinate_System_Definition:
Altitude_System_Definition:
Altitude_Datum_Name: National Geodetic Vertical Datum of 1929
Altitude_Resolution: 1
Altitude_Distance_Units: feet
Altitude_Encoding_Method:
Explicit elevation coordinate included with horizontal coordinates
Entity_and_Attribute_Information:
Overview_Description:
Entity_and_Attribute_Overview:
Airborne survey specifications These items are constant for the entire survey Project number: VA17 Project name: Southern Piedmont, Virginia Survey flown by: GeoMetrics Survey flown for: Virginia Division of Mineral Resources Approx. no. of line miles: 2000 Survey height: 500 ft Altitude method: Draped over terrain Flight-line spacing: 0.5 mi Flight-line direction: E-W Aircraft used: unknown Airport - arrival: unknown Airport - departure: unknown Sensor tow distance: unknown Magnetometer used: Geometrics Data recording interval: unknown Regional field removed: DGRF
Entity_and_Attribute_Detail_Citation:
Nettleton, L.L., 1971, Elementary Gravity and Magnetics for Geologists and Seismologists: Society of Exploration Geophysicists Monograph Series No. 1. Dobrin, M.B., 1976, Introduction to Geophysical Prospecting: New York, McGraw-Hill Book Company, Sheriff, R.E., 1984, Encyclopedic dictionary of exploration geophysics: Tulsa, OK, Society of Exploration Geophysicists.
Distribution_Information:
Distributor:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization:
Web site administration: U.S Geological Survey Publishing Service Center
Contact_Address:
Address_Type: mailing address
Address:
Publishing Service Center
USGS MS 902, Box 25046 DFC
City: Denver
State_or_Province: CO
Postal_Code: 80225-0046
Contact_Voice_Telephone: 303-236-5486
Distribution_Liability:
Although all data published on this web site have been used by the 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 or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: ASCII
Format_Specification:
Each line contains data in the following format, beginning with line 1 (no header included): line_no I5 flight line number directn I4 flight line direction, azimuth degrees from north longitud F11.4 longitude (decimal degrees) latitude F9.4 latitude (decimal degrees) year I5 year flown jul_day I4 Julian day flown fiducial I7 fiducial number radar F8.1 radar altitude above ground (feet) barom F8.1 barometric altitude above mean sea level (feet) totmag F9.2 corrected total field magnetic value (nT) resmag F9.2, 1X residual magnetic value (nT)
File_Decompression_Technique: gunzip
Format_Version_Number: 4.1
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Network_Address:
Network_Resource_Name:
Fees: none
Distribution_Information:
Distributor:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Peter N Schweitzer
Contact_Organization: USGS Eastern Mineral and Environmental Resources Science Center
Contact_Position: Geologist
Contact_Address:
Address_Type: mailing address
Address: 12201 Sunrise Valley Drive
City: Reston
State_or_Province: VA
Postal_Code: 20192-0002
Country: USA
Contact_Voice_Telephone: 703-648-6533
Contact_Facsimile_Telephone: 703-648-6252
Contact_Electronic_Mail_Address: pschweitzer@usgs.gov
Resource_Description: VA_VA17_meta.txt
Distribution_Liability:
This dataset was prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.
Standard_Order_Process:
Digital_Form:
Digital_Transfer_Information:
Format_Name: CSV
Format_Information_Content: Flight-line airborne magnetic anomaly measurements
File_Decompression_Technique: unzip
Transfer_Size: 0.93703365325928
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Fees: none
Metadata_Reference_Information:
Metadata_Date: 20141205
Metadata_Contact:
Contact_Information:
Contact_Organization_Primary:
Contact_Organization: USGS Crustal Geophysics and Geochemistry Science Center
Contact_Address:
Address_Type: mailing address
Address:
Magnetic and Gravity Information
U.S. Geological Survey
Box 25046 Mail Stop 964
Denver Federal Center
City: Denver
State_or_Province: CO
Postal_Code: 80225-0046
Contact_Voice_Telephone: 303-236-5652
Metadata_Standard_Name: Content Standard for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998

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