Identification_Information: Citation: Citation_Information: Originator: Robert P. Kucks Publication_Date: 1999 Title: Magnetic Anomaly Data Grid Description: Abstract: The grid of magnetic anomaly data for the conterminous United States and adjacent marine areas was created from digitized contours from three regional sources. Purpose: Magnetic anomalies are produced by variations in the distribution of iron minerals, usually magnetite, in the rocks of the Earth's crust. Igneous and metamorphic rocks can be very magnetic. By comparison, sedimentary rocks are usually nonmagnetic. Magnetic anomalies therefore provide a way of mapping exposed and buried crystalline rocks Supplemental_Information: Digital Data Series DDS-9 (CD-ROM) contains gridded geophysical data (magnetics only defined here) images generated from the data, software for displaying and analyzing the images, software for processing potential-field geophysical data, and documentation files that describe the data and software. Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 1998 Ending_Date: 1999 Currentness_Reference: reprocessing for SDD website Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -125 East_Bounding_Coordinate: -65 North_Bounding_Coordinate: 49 South_Bounding_Coordinate: 25 Access_Constraints: None Use_Constraints: None Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Robert P. Kucks Contact_Organization: U.S. Geological Survey Contact_Address: Address_Type: mailing address Address: Box 25046, MS 964 Denver Federal Center City: Denver State_or_Province: CO Postal_Code: 80225-0046 Country: USA Contact_Voice_Telephone: (303) 236-1405 Contact_Electronic_Mail_Address: rkucks@usgs.gov Data_Set_Credit: The composite grid was the product of digitization of an eastern and western US magnetic contour map produced by the USGS with additional data used in the compilation of the North American map by the Geological Society of America. USGS employees: Godson, Bond, Zietz Native_Data_Set_Environment: At the USGS, these data are stored in several binary gridded data formats on UNIX and PC systems. Data have been distributed in GEOSOFT GXF (an ASCII interchange format), Arc/Info export (e00), and ER Mapper binary format. Keywords: Theme: Theme_Keyword_Thesaurus: none Theme_Keyword: aeromagnetic Place: Place_Keyword_Thesaurus: none Place_Keyword: United States Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: Grid values represent the total intensity of the Earth's magnetic field after removal of a regional gradient present in the eastern US map. Measurements were made by a variety of magnetometer systems with typical accuracy of 1 to 10 nanotesla (nT). In addition to corrections for the IGRF, the original individual magnetic surveys typically contain corrections for the diurnal variations of the Earth's magnetic field that occurred during the flight (as recorded by a base station magnetometer) and leveling adjustments made at flightline intersections. The absolute accuracy of the gridded data are probably better than 5 nanotesla, with accuracy increasing for with increasing wavelength. A final grid interval of 2 km was chosen as representative. Quantitative_Attribute_Accuracy_Assessment: Attribute_Accuracy_Value: 2 to 5 nanotesla, dependent on wavelenth of anomalies. Attribute_Accuracy_Explanation: See Attribute_Accuracy_Report Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: Horizontal position of the survey aircraft used to collect data being integrated to generate the grid were determined by various means. Older surveys (1945-1960s) were positioned by reconciling down-looking photographs with topographic maps and orthophoto quad maps. Later surveys used various standard aircraft navigation aids as they became available. Quantitative_Horizontal_Positional_Accuracy_Assessment: Horizontal_Positional_Accuracy_Value: 500 Horizontal_Positional_Accuracy_Explanation: See Horizontal_Positional_Accuracy_Report Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: The individual aeromagnetic surveys that make up this data set were flown at various fixed barometric altitudes and as draped surveys with constant terrain clearance specifications. Quantitative_Vertical_Positional_Accuracy_Assessment: Vertical_Positional_Accuracy_Value: 100 Vertical_Positional_Accuracy_Explanation: See Vertical_Positional_Accuracy_Report Lineage: Process_Step: Process_Description: Magnetic grid was extracted from DDS-9 and reprojected using USGS in-house developed software. In-house software was also used to convert from USGS grid format to Arc-Info grid format. Source_Used_Citation_Abbreviation: The "state-of-the-art" for aeromagnetic data collection changed significantly throughout the data collection period for this data set. Journals such as GEOPHYSICS have periodic articles describing the current state of standard procedures. Process_Date: 1999 Process_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Robert P. Kucks Contact_Organization: U.S. Geological Survey Contact_Address: Address: Box 25046, MS 964 Denver Federal Center City: Denver State_or_Province: CO Postal_Code: 80225-0046 Country: USA Address_Type: mailing address Contact_Electronic_Mail_Address: rkucks@usgs.gov Contact_Voice_Telephone: (303)236-1405 Logical_Consistency_Report: The flight data collected to generate the final gridded product is dependent on the individual contractor. All corresponding corrections were then made by the contractor and a final data set was presented for gridding. Compositing of the individual surveys was done in an analog process before digitizing. The process of reprojecting the grid does not affect the accuracy of the product. Completeness_Report: The best resolution (spacing and flight height) flight data was used to generate the compilation. See corresponding indices in original publications for specifications. Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Raster Raster_Object_Information: Raster_Object_Type: Grid cell Row_Count: 1471 Column_Count: 2601 Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Map_Projection: Albers_Conical_Equal_Area: Standard_Parallel: 29.5 Standard_Parallel: 45.5 Longitude_of_Central_Meridian: -96.0 Latitude_of_Projection_Origin: 37.5 False_Easting: 0. False_Northing: 0. Map_Projection_Name: Albers Conical Equal Area Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: row and column Coordinate_Representation: Abscissa_Resolution: 2.0 Ordinate_Resolution: 2.0 Planar_Distance_Units: kilometer Geodetic_Model: Horizontal_Datum_Name: Noth American Datum of 1927 Ellipsoid_Name: CLARKE1866 Semi-major_Axis: 6378.20640 Denominator_of_Flattening_Ratio: 0.99661 Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: Residual total intensity of Earth's magnetic field Entity_Type_Definition: Ascii, scientific notation real number value Entity_Type_Definition_Source: Well established geophysical data quantity Attribute: Attribute_Label: Residual total intensity of Earth's magnetic field Attribute_Definition: Value, in nanoTesla, of total intensity of Earth's magnetic field after removal of the theoretical International Geomagnetic Reference Field value. Attribute_Definition_Source: Paterson, N.R., and Reeves, C.V., 1985, Applications of gravity and magnetic surveys: The state-of-the-art in 1985: Geophysics, v. 50, p. 2558-2594. Attribute_Domain_Values: Range_Domain: Range_Domain_Minimum: -1393 Range_Domain_Maximum: 2502 Attribute_Units_of_Measure: nanoTesla Attribute_Measurement_Resolution: 1.0 Unrepresentable_Domain: Cells with a value of 0.170141173E+39 represent areas of no data in grid. Attribute_Value_Accuracy_Information: Attribute_Value_Accuracy_Explanation: See discussion in Attribute_Accuracy_Report of Data_Quality_Information. Attribute_Value_Accuracy: 10.0 Distribution_Information: Distributor: Contact_Information: Contact_Voice_Telephone: (303)236-7476 Contact_Address: Address_Type: mailing address Address: Box 25286, Building 810 Denver Federal Center City: Denver State_or_Province: CO Postal_Code: 80225 Country: USA Contact_Organization_Primary: Contact_Organization: USGS Map Distribution Resource_Description: Digital Data Series DDS-9 has the original grid before reprojection and format conversion Distribution_Liability: The USGS has made every effort to verify the veracity of this information, but is not liable for any inaccuracies. Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: ARCE Format_Specification: Arc-Info grid format Format_Information_Content: gridded data File_Decompression_Technique: gunzip Transfer_Size: 12.8 Format_Version_Date: 1993 Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: anonymous FTP (File Transfer Protocol) Access_Instructions: anonymous FTP to musette.cr.usgs.gov file available as pub/cdrom_DDS-9/ARC_INFO/magnetic_sdd.e00.gz Online_Computer_and_Operating_System: Hewlett Packard K220 UNIX server - HPUX 10.2 Offline_Option: Offline_Media: CD-ROM Recording_Format: ISO 9660 Compatibility_Information: The access software used on the disc currently executes only under DOS/WINDOWS on IBM or compatible computers. Fees: FTP and website are no cost unknown for CD_ROM, DDS-9 may be out of print Ordering_Instructions: contact above address or phone Turnaround: unknown Technical_Prerequisites: see Compatibility_Information for CD_ROM DDS-9: CD-ROM driver software super VGA video system for FTP of grid: FTP software Available_Time_Period: Time_Period_Information: Single_Date/Time: Calendar_Date: 1999 Metadata_Reference_Information: Metadata_Date: 19990329 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Robert P. Kucks Contact_Organization: U.S. Geological Survey Contact_Electronic_Mail_Address: rkucks@usgs.gov Contact_Address: Address_Type: mailing address Address: Box 25046, MS 964 Denver Federal Center City: Denver State_or_Province: CO Postal_Code: 80225 Country: USA Contact_Voice_Telephone: (303)236-1405 Metadata_Standard_Name: FGDC Content Standard for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998