Identification_Information:
  Citation:
    Citation_Information:
      Originator: V.E. Langenheim, Shawn Biehler, D.K. McPhee, C.A. McCabe, J.T. Watt, M. Anderson, B.A. Chuchel, and P. Stoffer
      Publication_Date: 2007
      Title:
        Preliminary isostatic gravity map of Joshua Tree National Park and vicinity, southern California, California
      Edition: rev 1.0
      Publication_Information:
        Publication_Place: U.S. Geological Survey, Menlo Park, CA
        Publisher: U.S. Geological Survey
      Online_Linkage: http://pubs.usgs.gov/of/2007/1218/
  Description:
    Abstract: Gravity data were compiled, collected, and edited to produce an isostatic gravity map of Joshua Tree National Park and vicinity, California.
    Purpose: To provide basic geophysical information to regional mapping and hydrologic studies
  Point_of_Contact:
    Contact_Information:
      Contact_Person_Primary:
        Contact_Person: Victoria Langenheim
        Contact_Organization: U.S. Geological Survey
      Contact_Address:
        Address: 345 Middlefield Rd. MS 989
        City: Menlo Park
        State_or_Province: CA
        Postal_Code: 94025
        Country: USA
        Address_Type: mailing and physical address
      Contact_Voice_Telephone: 650-329-5313
  Spatial_Domain:
    Bounding_Coordinates:
      West_Bounding_Coordinate: -116.5
      East_Bounding_Coordinate: -115.083
      North_Bounding_Coordinate: 33.53
      South_Bounding_Coordinate: 34.25
  Native_Data_Set_Environment:
    data was stored and analysed on a SUN Ultra4000 UNIX platform
  Status:
    Progress: Preliminary report
    Maintenance_and_Update_Frequency: none planned
  Keywords:
    Place:
      Place_Keyword: California, Joshua Tree National Park
    Theme:
      Theme_Keyword: gravity, density, isostatic anomaly
  Access_Constraints: none
  Use_Constraints: none
Data_Quality_Information:
  Positional_Accuracy:
    Horizontal_Positional_Accuracy:
      Horizontal_Positional_Accuracy_Report:
        Accuracy of the point data is roughly 40m, as well as the data can be located on a 1:24,000-scale topographic map
    Vertical_Positional_Accuracy:
      Vertical_Positional_Accuracy_Report:
        Accuracy of the point data vary; most of the elevations are accurate to 10 feet or less.  In some of the more mountainous areas, the accuracy may fall to 20 to 40 feet.
  Attribute_Accuracy:
    Attribute_Accuracy_Report:
      Observed gravity data are accurate to 0.05 mGal; reduced anomalies are accurate to 1-2 mGal.  Data are more accurate in the valleys than in the mountains because of uncertainties in elevation and in the terrain correction.
  Logical_Consistency_Report: see open-file report
  Completeness_Report:
    Dataset based on geophysical analysis.  see
    open-file report.
  Lineage:
    Source_Information:
      Source_Citation:
        Citation_Information:
          Originator: Roberts, C.W., Jachens, R.C., and Oliver, H.W.
          Publication_Date: 1990
          Title:
            Isostatic gravity map of California and offshore southern California
          Series_Information:
            Series_Name: California Division of Mines and Geology Geologic Data Map NO. 7
          Edition: first edition
Spatial_Reference_Information:
  Horizontal_Coordinate_System_Definition:
    Geodetic_Model:
      Horizontal_Datum_Name:
        Geographic
        NAD27
      Ellipsoid_Name: CLARKE 1866
Entity_and_Attribute_Information:
  Detailed_Description:
    Entity_Type:
      Entity_Type_Definition: Point_Type
  Overview_Description:
    Entity_and_Attribute_Overview:
      The data file is in ASCII format.  The data define point data with information as follows:
      STATION NAME (a8) .............An alphanumeric combination of up to 
                                  8 characters used for station identification; 
      LAT (f3.0,f4.2)................Latitude in degrees and minutes, 
                                     to 0.01 minute; 
      LON (f4.0,f4.2)................Longitude in degrees and minutes, 
                                     to 0.01 minute; 
      ELEV (f6.1)....................Elevation, to 0.1 ft; 
      OG (f7.2)......................Observed gravity, to 0.01 mGal; 
      FAA (f6.2) ....................Free-air anomaly to 0.01 mGal; 
      SBA (f6.2).....................Simple Bouguer anomaly to 0.01 mGal; 
      ITC (f5.2).....................Inner terrain correction for a density 
                                  of 2.67 g/cc, to 0.01 mGal, followed by a
				  letter denoting the extent of the correction.
				  "Z" indicates computer terrain correction 
				  from the station out to 166.7 km with inner
				  terrain correction out to D zone; 
      TC (f5.2)......................Total terrain correction from the station
                                  to 166.7 km for a density of 2.67 g/cc, to 
                                  0.01 mGal; 
      TC CODE (a1)................Letter denoting the extent of the 
                                  correction, according to the Hayford-Bowie 
                                  template (e.g. 'D' means 590 meters); 
      CBA (f6.2)...................Complete Bouguer anomaly reduced for a
				  density of 2.67 g/cc, to 0.01 mGal; 
      ISO (f6.2)..................Isostatic residual anomaly values assuming 
                                  an Airy model for isostatic compensation 
                                  of topographic loads.  This model assumes a
			 	  a crustal thickness of 25 km, a topographic
				  load density of 2.67 g/cc, and a density 
				  contrast across the base of the model crust
				  of 0.4 g/cc.
  Overview_Description:
    Entity_and_Attribute_Overview:
      point data representing gravity data
Metadata_Reference_Information:
  Metadata_Date: 20070918
  Metadata_Standard_Name: FGDC Content Standards for Digital Geospatial Metadata