Identification_Information: Citation: Citation_Information: Originator: V.E. Langenheim Originator: R.C. Jachens PPublication_Date: 2014 Title: Magnetic data, processing, and maps of Fort Irwin and vicinity, southern California Geospatial_Data_Presentation_Form: point digital data Series_Information: Series_Name: Open-File Report Issue_Identification: 2013-1024–I Publication_Information: Publication_Place: Menlo Park, CA Publisher: U.S. Geological Survey Online Linkage: http://pubs.usgs.gov/of/2013/1024/i/ Description: Abstract: Helicopter magnetic data of the Leach Basin area, magnetic gradients, aeromagnetic data for the Soda Lake region, a grid of the detailed aeromagnetic data, and magnetic susceptibility data for Fort Irwin and vicinity, southern California Digital Files: an ASCII file containing point magnetic data from the Leach Basin helicopter survey, an ASCII file containing point magnetic data from the Soda Lake aeromagnetic survey, a grid of detailed aeromagnetic data from the Fort Irwin region, two ASCII files with point locations of the local maximum horizontal gradient derived from the magnetic grid, and one of magnetic susceptibility data. This metadata file describes the gridded magnetic data. Purpose: Magnetic map identifies magnetic features as a basis for geophysical interpretations. Supplemental_Information: This database updates geophysical information originally presented in smaller scale formats and includes detailed aeromagnetic data collected by Aeroquest International and by Firefly Aviation, Ltd. Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 1982 Ending_Date: 2011 Currentness_Reference: publication date Status: Progress: Complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -117.276 East_Bounding_Coordinate: -116.040 North_Bounding_Coordinate: 35.907 South_Bounding_Coordinate: 34.726 Keywords: Theme: Theme_Keyword: magnetics Theme_Keyword: magnetic anomaly Place: Place_Keyword: southern California Place_Keyword: Mojave Desert Place_Keyword: Fort Irwin Access_Constraints: none Use_Constraints: Uses of this digital data should not violate the spatial or attribute resolution of the data. Although the digital form of the data stores location and attribute values to several decimals of precision, the data is subject to the accuracy and precision inherent in the data due to data collection and processing limitations. Where this data is used in combination with other data, the precision and accuracy of the resulting dataset is limited by the precision and accuracy of the input datasets. Acknowledgement of the U.S. Geological Survey and Pacific Gas and Electric Company is appreciated for products derived from these data. Point_of_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Victoria Langenheim Contact_Organization: U.S. Geological Survey Contact_Position: geophysicist Contact_Address: Address_Type: physical address Address: 345 Middlefield Rd. City: Menlo Park State_or_Province: CA Postal_Code: 94025 Country: USA Contact_Voice_Telephone: 650-329-5313 Contact_Electronic_Mail_Address: zulanger@usgs.gov Native_Data_Set_Environment: Geosoft Oasis Montaj Native_Data_Set_Environment: Geosoft Oasis Montaj Geophysical data was stored and analyzed on a SUN Ultra4000 UNIX platform Geospatial_Data_Presentation_Form: ascii digital data (aeromagnetic data) Series_Information: Series_Name: U.S. Geological Survey (USGS) Open-File Report Issue_Identification: 2012-XXXX Publication_Information: Publication_Place: Menlo Park, California Publisher: U.S. Geological Survey Online_Linkage: Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: magnetic field values are reported to 0.001 nT Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: accuracy should be within 250 meters (grid cell size) Lineage: Process_Step: Process_Description: Data from detailed aeromagnetic surveys were interpolated to a rectangular grid with nodes spaced 250 m apart using a minimum curvature algorithm (Briggs, 1974) using a Transverse Mercator projection (central meridian -117.0; base latitude 0.0; scale factor 0.9996). Process_Date: 2012 Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Point Point_and_Vector_Object_Information: SDTS_Terms_Description: SDTS_Point_and_Vector_Object_Type: Entity point Point_and_Vector_Object_Count: 177163 Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Geographic: Latitude_Resolution: 0.0001 Longitude_Resolution: 0.001 Geographic_Coordinate_Units: Decimal degrees Geodetic_Model: Horizontal_Datum_Name: North American Datum of 1929 Ellipsoid_Name: Clarke 1866 Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: mag_hires_grid.xyz Attribute: Attribute_Label: magnetic_field Attribute_Definition: gridded magnetic field from detailed aeromagnetic data Attribute: Attribute_Label: lon_nad27 Attribute_Definition: longitude coordinate Attribute_Value_Accuracy_Information: Attribute_Value_Accuracy: 250 m Attribute: Attribute_Label: lat_nad27 Attribute_Definition: latitude coordinate Attribute_Value_Accuracy_Information: Attribute_Value_Accuracy: 250 m Distribution_Information: Distributor: U.S. Geological Survey Resource_Description: Downloadable Data Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: ASCII Transfer_Size: 6023993 Network_Resource_Name: http://pubs.usgs.gov/of/2012/XXXX Process_Date: 2009-2012 Process_Step: Process_Description: Geophysical mapping The gridded magnetic values are derived from a compilation of the newly flown aeromagnetic data (this report) and previously published magnetic data. The magnetic data were compiled from existing publications (U.S. Geological Survey, 1985; Roberts and Jachens, 1999; U.S. Geological Survey and National Geophysical Data Center, 2002) and the data were interpolated to a regular grid (Briggs, 1974) with cell dimensions of 250 m in both the X and Y directions. Scale factor 0.9996, false easting and northing, zero. The magnetic base levels were then adjusted to a common magnetic datum used in previous magnetic surveys, with a 1-km gap separating the various surveys. Baranov, V.I., 1957, A new method for interpretation of aeromagnetic maps--pseudo-gravimetric anomalies: Geophysics, v. 22, p. 359-383. Blakely, R.J., and Simpson, R.W., 1986, Approximating edges of source bodies from magnetic or gravity anomalies: Geophysics, v. 51, p. 1494-1498. Briggs, I., 1974, Machine contouring using minimum curvature: Geophysics, v. 39, no. 1, p. 39-48. Roberts, C.W., and Jachens, R.C., 1999, Preliminary aeromagnetic anomaly map of California: U.S. Geological Survey Open-File Report 99-440, 14 p. Also available at http://geopubs.wr.usgs.gov/open-file/of99-440/ (last accessed 8/31/2011). U.S. Geological Survey, 1985, Aeromagnetic map of the Ord Mountains, southern California: U.S. Geological Survey Open-File Report 87-005, 9 sheets, scale 1:62,500. U.S. Geological Survey and National Geophysical Data Center, 2002, Aeromagnetic datasets for the conterminous United States and Hawaii: U.S. Geological Survey Open-File Report 02-361. Available at http://pubs.usgs.gov/of/2002/ofr-02-361/ (last accessed 8/31/2011). Metadata_Reference_Information: Metadata_Date: 20120711 Metadata_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Victoria Langenheim Contact_Organization: U.S. Geological Survey Contact_Position: geophysicist Contact_Address: Address_Type: mailing and physical address Address: 345 Middlefield Rd. City: Menlo Park State_or_Province: CA Postal_Code: 94025 Contact_Voice_Telephone: 650-329-5313 Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 Metadata_Time_Convention: local time Metadata_Extensions: Online_Linkage: http://www.esri.com/metadata/esriprof80.html Profile_Name: ESRI Metadata Profile