Isostatic residual gravity anomaly data grid for the conterminous US

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Metadata:

Identification_Information:
Citation:
Citation_Information:
Originator: Robert P. Kucks
Publication_Date: 1999
Title:
Isostatic residual gravity anomaly data grid for the conterminous US
Online_Linkage: Larger_Work_Citation:
Citation_Information:
Originator: Phillips, Jeffrey D.
Originator: Duval, Joseph S.
Originator: Ambroziak, Russell A.
Publication_Date: 1993
Title:
National geophysical data grids; gamma-ray, gravity, magnetic and topographic data for the conterminous United States
Series_Information:
Series_Name: U.S. Geological Survey Digital Data Series
Issue_Identification: DDS-9
Online_Linkage: http://pubs.er.usgs.gov/publication/ds9
Description:
Abstract:
The grid of isostatic residual gravity anomaly data was produced from the grid of Bouguer gravity anomaly data (see Bouguer gravity metadata) by using an Airy-Heiskanen compensation model with three parameters. The depth to the compensating root at sea level was chosen to be 30 km. The density contrast across the root was chosen to be 0.35 grams per cubic centimeter, and the the density of the topography was chosen to be 2.67 grams per cubic centimeter.
Purpose:
Isostatic residual gravity anomaly maps are produced by subtracting long-wavelength anomalies produced by masses deep within the crust or mantle from the Bouguer anomaly map. The long-wavelength anomalies are assumed to result from isostatic compensation of topographic loads. Isostatic residual gravity anomaly maps therefore reveal more clearly than Bouguer gravity anomaly maps the density distributions within the upper crust that are of interest in many geologic and tectonic studies.
Supplemental_Information:
Digital Data Series DDS-9 (CD-ROM) contains gridded geophysical data (isostatic gravity anomaly data 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
Keywords:
Theme:
Theme_Keyword_Thesaurus: USGS Thesaurus
Theme_Keyword: isostatic anomaly
Theme_Keyword: gravitational field (earth)
Theme_Keyword: geophysics
Theme_Keyword: geospatial datasets
Theme:
Theme_Keyword_Thesaurus: ISO 19115 Topic Category
Theme_Keyword: geoscientificInformation
Place:
Place_Keyword_Thesaurus: none
Place_Keyword: United States
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 compilation of onshore data consisted of nearly one million Bouguer gravity anomaly values computed by using a reduction density of 2.67 grams per cubic centimeter. The offshore data consisted of approximately 800,000 free-air gravity anomaly values. The isostatic calculation was produced from these data

USGS employees: Simpson and Jachens
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.
Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
Initially the accuracy of the gravity anomaly value for each station is critical. Choices of the parameters used to calculate isostatic gravity are dependent on the geologic and tectonic setting and are subject to the discretion of the person carrying out the calculations.

Gravity measurements made on the surface of the Earth must be corrected in various way before they can be made into an anomaly map. The free-air correction reduces the measurement to sea level by assuming there is no intervening mass as a uniform slab of constant density, and the complete Bouguer correction includes the effects of constant density topography within 166.7 km of the measurement location. A gravity reference field is subtracted from the corrected measurements to produce the free-air, simple Bouguer, or complete Bouguer anomaly. The data set constitutes many years of individual collection of gravity stations and therefore is difficult to access the precise accuracy.
Quantitative_Attribute_Accuracy_Assessment:
Attribute_Accuracy_Value: less than 2 milligals
Attribute_Accuracy_Explanation: overall station accuracy
Logical_Consistency_Report:
The accuracy of the data set that generated the grid is totally dependant on the individual who collected each gravity station. In the case of a national set they would number in the hundreds. Variations would include latitude, longitude, elevation, raw gravity reading and base station control.
Completeness_Report:
There will always be upgrades and additions to the data set that generated the grid due to regional interests.
Positional_Accuracy:
Horizontal_Positional_Accuracy:
Horizontal_Positional_Accuracy_Report:
Earlier collection of stations was by surveying methods. Positions were also acquired from locations on topographic maps. Recently the station latitudes, longitudes and elevations were acquired by Geopositioning Satellite (GPS) systems.
Quantitative_Horizontal_Positional_Accuracy_Assessment:
Horizontal_Positional_Accuracy_Value: 100
Horizontal_Positional_Accuracy_Explanation:
surveying methods - 1.0 meter topographic maps - 3.0 meter GPS systems - 100.0 meter/1.0 meter differential
Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report: see Horizontal_Positional_Accuracy_Report
Quantitative_Vertical_Positional_Accuracy_Assessment:
Vertical_Positional_Accuracy_Value: 100
Vertical_Positional_Accuracy_Explanation:
surveying methods - 1.0 meter topographic maps - 1.0-20.0 meter GPS systems - 100 meter/1.0 meter differential
Lineage:
Process_Step:
Process_Description:
Isostatic residual gravity anomaly 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 gravity 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_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
Spatial_Data_Organization_Information:
Direct_Spatial_Reference_Method: Raster
Raster_Object_Information:
Raster_Object_Type: Grid cell
Row_Count: 768
Column_Count: 1300
Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Map_Projection:
Map_Projection_Name: Albers Conical Equal Area
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.
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: row and column
Coordinate_Representation:
Abscissa_Resolution: 4.0
Ordinate_Resolution: 4.0
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: grid cell
Entity_Type_Definition: Area of Earth's surface for which gravity anomaly is summarized
Entity_Type_Definition_Source: this dataset
Attribute:
Attribute_Label: cell value
Attribute_Definition:
Value, in milligals, of the gravity anomaly of Earth's gravitational field.
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: -225
Range_Domain_Maximum: 105
Attribute_Units_of_Measure: milligal
Attribute_Measurement_Resolution: 0.1
Attribute_Domain_Values:
Enumerated_Domain:
Enumerated_Domain_Value: -0.3402823E+39
Enumerated_Domain_Value_Definition: areas for which no data are available in the grid
Enumerated_Domain_Value_Definition_Source: this dataset
Distribution_Information:
Distributor:
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
Country: USA
Contact_Voice_Telephone: (303)236-1405
Contact_Electronic_Mail_Address: rkucks@usgs.gov
Resource_Description: USGS Digital Data Series DDS-9
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: ArcInfo export
Format_Version_Number: 7.x
Format_Specification: Arc-Info grid format
Format_Information_Content: Gridded gravity anomaly data
File_Decompression_Technique: gunzip
Transfer_Size: 3.5
Digital_Transfer_Option:
Online_Option:
Digital_Form:
Digital_Transfer_Information:
Format_Name: GeoTiff
Format_Version_Number: 6
Format_Information_Content: Gridded gravity anomaly data
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Digital_Form:
Digital_Transfer_Information:
Format_Name: OGC WMS
Format_Version_Number: 1.3.0
Format_Information_Content: Isostatic gravity anomaly
Digital_Transfer_Option:
Online_Option:
Computer_Contact_Information:
Fees: none
Metadata_Reference_Information:
Metadata_Date: 20201229
Metadata_Contact:
Contact_Information:
Contact_Person_Primary:
Contact_Person: Peter N Schweitzer
Contact_Organization: USGS Geology, Energy, and Minerals 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
Metadata_Standard_Name: Content Standard for Digital Geospatial Metadata
Metadata_Standard_Version: FGDC-STD-001-1998

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