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Aeromagnetic data for Wind River Basin, Wyoming

Metadata:

• Identification_Information
• Data_Quality_Information
• Spatial_Data_Organization_Information
• Spatial_Reference_Information
• Entity_and_Attribute_Information
• Distribution_Information
• Distribution_Information
• Metadata_Reference_Information

Identification_Information:

Citation:

Citation_Information:

Originator: U.S. Geological Survey

Originator: National Geophysical Data Center

Publication_Date: 2002

Title: Aeromagnetic data for Wind River Basin, Wyoming

Geospatial_Data_Presentation_Form: tabular digital data

Larger_Work_Citation:

Citation_Information:

Originator: U.S. Geological Survey

Originator: National Geophysical Data Center

Publication_Date: 2001

Title:

Digital flight-line aeromagnetic data sets of the Conterminous United States, Hawaii, and Puerto Rico

Series_Information:

Series_Name: U.S. Geological Survey Open-File Report

Issue_Identification: 02-361

Publication_Information:

Publication_Place: Denver, CO

Publisher: U.S. Geological Survey

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. Aeromagnetic anomaly maps are important tools in mapping surficial and buried igneous rocks. 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.

Supplemental_Information:

The U.S. Geological Survey has contracted or flown numerous airborne surveys over a long period (1950's to present). Not all flight-line data have been released to the public because of lack of personnel to reformat data and service the requests. With the improvement in digital communication and the ability to store and transmit large data sets, the USGS is now able to release the flight-line data in a common format.
A companion CD-ROM/web site has been released containing magnetic data that were generated by digitizing analog maps. Digital flight-line data used to create the analog maps are unavailable. Reference is in the Cross-Reference section of this metadata file.

Time_Period_of_Content:

Time_Period_Information:

Range_of_Dates/Times:

Beginning_Date: 197405

Ending_Date: 197406

Currentness_Reference:

Time period indicates dates of airborne survey data collection. Time period is expressed in the format YYYYMM or YYYYMMDD when further accuracy is available.

Status:

Progress: complete

Maintenance_and_Update_Frequency: none planned

Spatial_Domain:

Bounding_Coordinates:

West_Bounding_Coordinate: -109.87

East_Bounding_Coordinate: -105.50

North_Bounding_Coordinate: 43.50

South_Bounding_Coordinate: 42.17

Data_Set_G-Polygon:

Data_Set_G-Polygon_Outer_G-Ring:

G-Ring:

-109.87 43.50, -106.82 43.50, -105.50 42.17, -108.52 42.17, -109.87 43.50

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: ISO 19115 Topic Categories

Theme_Keyword: geoscientificInformation

Place:

Place_Keyword_Thesaurus: none

Place_Keyword: United States

Place_Keyword: Wyoming

Place_Keyword: WY

Place_Keyword: Wind River Basin

Place_Keyword: Casper

Place:

Place_Keyword_Thesaurus: Augmented FIPS 10-4 and FIPS 6-4, version 1.0

Place_Keyword: 56001 = Albany

Place_Keyword: 56007 = Carbon

Place_Keyword: 56009 = Converse

Place_Keyword: 56013 = Fremont

Place_Keyword: 56025 = Natrona

Place_Keyword: 56037 = Sweetwater

Place_Keyword: 56043 = Washakie

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.

Point_of_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: USGS Gravity and Magnetics Contact

Contact_Address:

Address_Type: mailing address

Address:

U.S. Geological Survey
Box 25046 Mail Stop 964
Denver Federal Center

City: Denver

State_or_Province: CO

Postal_Code: 80225

Contact_Voice_Telephone: 303-236-1343

Contact_Electronic_Mail_Address: grav_mag@usgs.gov

Browse_Graphic:

Browse_Graphic_File_Name:

<ftp://ftpmusette.cr.usgs.gov/pub/NA_MAGNETICS/digital_data/WY/WY_6001.jpg>

Browse_Graphic_File_Description:

An image of the flight lines showing total magnetic intensity along the flight lines.

Browse_Graphic_File_Type: JPEG

Data_Set_Credit:

These USGS employees contributed to reformatting and archiving these data:
Viki Bankey, 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 running a Windows NT operating system. Data were reformatted using the Geosoft, Inc., program Oasis Montaj version 4.3.

Cross_Reference:

Citation_Information:

Originator: U.S. Geological Survey

Publication_Date: 1999

Title:

Digitized Aeromagnetic Datasets of the Conterminous United States, Hawaii, and Puerto Rico

Geospatial_Data_Presentation_Form: raster digital data

Series_Information:

Series_Name: U.S. Geological Survey Open-File Report

Issue_Identification: 99-557

Publication_Information:

Publication_Place: Denver CO

Publisher: U.S. Geological Survey

Online_Linkage: <http://greenwood.cr.usgs.gov/pub/open-file-reports/ofr-99-0557>

Cross_Reference:

Citation_Information:

Originator: U.S. Atomic Energy Commission

Publication_Date: 1975

Title: Airborne geophysical survey, Wind River Basin area, Wyoming

Geospatial_Data_Presentation_Form: map

Series_Information:

Series_Name: Grand Junction Office Report

Issue_Identification: GJO-1631-1

Publication_Information:

Publication_Place: Grand Junction, Colorado

Publisher: U.S. Atomic Energy Commission

Other_Citation_Details:

by Texas Instruments, Inc., 118 sheets, 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.
The contractor database did not have flight line direction (directn), year (year), or fiducial (fiducial). A dummy value of -1 was used in the directn channel to conform to the established template. The values in the fiducial channel were generated with Oasis Montaj using the latitude channel as a reference.

Positional_Accuracy:

Horizontal_Positional_Accuracy:

Horizontal_Positional_Accuracy_Report:

Flight Path Recovery
Horizontal position of the survey aircraft used to collect data were determined by reconciling down-looking photographs (recorded on continuous-strip film) with topographic maps and orthophotoquadrangle maps. Fiducial numbers and marks, impressed on any paper strips that were recording data or added to magnetic tape records, were included as a function of time to further reconcile location with instrumentation.

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)
The magnetometer was carried in a bird towed on a line that was approximately 100 feet below the aircraft. The bird as it is towed is slightly behind the aircraft and, therefore, the vertical distance between the magnetometer and the aircraft is slightly less than the length of the line but remains constant for the survey.
This data set was collected at a draped survey having an average terrain clearance of 400 feet. 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 Attribute Accuracy Report, 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: 1974

Process_Step:

Process_Description:

USGS reformatting of contractor data to standard format.
USGS personnel used the software package Oasis Montaj version 5.1 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). Information was added that was missing from the data file but was recorded elsewhere. The reformatted data file was written in the format described in the section on Entity_and_Attribute_Overview.

Process_Date: 200301

Spatial_Data_Organization_Information:

Direct_Spatial_Reference_Method: point

Spatial_Reference_Information:

Horizontal_Coordinate_System_Definition:

Geographic:

Latitude_Resolution: .0001

Longitude_Resolution: .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: 6001
Project name: Wind River Basin, Wyoming
Survey compiled by: Texas Instruments, Inc.
Survey flown by: Texas Instruments, Inc.
Survey flown for: U.S. Atomic Energy Commission
Approx. no. of line miles: 8378
Survey height: 400 ft
Altitude method: Draped over terrain
Flight-line spacing: 2 mi
Flight-line direction: E-W
Aircraft used: Douglas DC-3
Airport - arrival: Casper, WY
Airport - departure: Casper, WY
Magnetometer used: GeoMetrics G-803 proton precession
Sensor tow distance: 100 feet

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, p. 83-87.
Dobrin, M.B., 1976, Introduction to Geophysical Prospecting: New York, McGraw-Hill Book Company, p. 505-517.

Overview_Description:

Entity_and_Attribute_Overview:

Each record contains the following 11 attributes:

No abbrev.name contents

1  line_no     flight line number
2  directn     flight line direction, azimuth degrees from north
(integer)
3  longitud    longitude (decimal degrees)
4  latitude    latitude (decimal degrees)
5  year        year flown (integer)
6  jul_day     Julian day flown (integer)
7  fiducial    fiducial number (integer)
8  radar       radar altimeter reading above ground (feet)
9  barom       altitude above mean sea level (feet)
10 totmag      corrected magnetic value (nT)
11 resmag      residual magnetic value (nT)

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, p. 83-87.
Dobrin, M.B., 1976, Introduction to Geophysical Prospecting: New York, McGraw-Hill Book Company, p. 505-517.

Detailed_Description:

Entity_Type:

Entity_Type_Label: record for one magnetic data point

Entity_Type_Definition:

The set of all measurements reported for a magnetic data point having the same spatial location.

Entity_Type_Definition_Source:

Standard aeromagnetic data collection procedures as written in the contract for survey collection.

Attribute:

Attribute_Label: line_no

Attribute_Definition: flight line number

Attribute_Definition_Source: often assigned by airborne survey crew

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 1

Range_Domain_Maximum: 542

Attribute_Units_of_Measure: alphanumeric value

Attribute:

Attribute_Label: directn

Attribute_Definition:

direction of flight line, azimuth degrees clockwise from north

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: -1

Range_Domain_Maximum: -1

Attribute_Units_of_Measure: degrees

Attribute:

Attribute_Label: longitud

Attribute_Definition: longitude - geographic coordinate

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: -109.8412

Range_Domain_Maximum: -105.5056

Attribute_Units_of_Measure: decimal degrees

Attribute:

Attribute_Label: latitude

Attribute_Definition: latitude - geographic coordinate

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 42.1644

Range_Domain_Maximum: 43.5055

Attribute_Units_of_Measure: decimal degrees

Attribute:

Attribute_Label: year

Attribute_Definition: year of data point collection

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 1974

Range_Domain_Maximum: 1974

Attribute:

Attribute_Label: jul_day

Attribute_Definition:

Julian day, where Jan. 1 = 1 and Dec. 31 = 365 or 366 (leap year)

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 126

Range_Domain_Maximum: 172

Attribute_Value_Accuracy_Information:

Attribute_Value_Accuracy: 31

Attribute_Value_Accuracy_Explanation:

Both beginning and end julian dates were taken from dataset.

Attribute:

Attribute_Label: fiducial

Attribute_Definition:

A fiducial number is a mark which indicates points of simultaneity. It is a user-defined integer used during airborne operations to correlate recording devices (magnetometers) with navigational records (altimeters, camera film, strip charts) that were recorded at the same time.

Attribute_Definition_Source:

Sheriff, R.E., 1984, Encyclopedic dictionary of exploration geophysics: Tulsa, OK, Society of Exploration Geophysicists, p. 89.

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 0

Range_Domain_Maximum: 76730

Attribute:

Attribute_Label: radar

Attribute_Definition:

radar altimetry reading, in feet
An aircraft navigational system in which short electromagnetic waves are transmitted, and the energy scattered back by reflection is detected. From this measurement, the distance between the aircraft and the ground is calculated and recorded as radar altimetry.
Values of -9999.9 indicate missing data.

Attribute_Definition_Source:

Sheriff, R.E., 1984, Encyclopedic dictionary of exploration geophysics: Tulsa, OK, Society of Exploration Geophysicists, p. 89.

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 216.0

Range_Domain_Maximum: 4645.9

Attribute_Units_of_Measure: feet

Attribute:

Attribute_Label: barom

Attribute_Definition:

altitude above mean sea level, in feet, measured using the barometer that is part of the aircraft navigation system
Values of -9999.9 indicate missing data.

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 5080.3

Range_Domain_Maximum: 14054.9

Attribute_Units_of_Measure: feet

Attribute:

Attribute_Label: totmag

Attribute_Definition:

Raw magnetic value with base magnetometer corrections applied.
Because the magnetic field of the earth varies diurnally, a stationary base magnetometer is maintained on the ground during airborne surveying. The base magnetometer records changes in the magnetic field (in nanoTeslas) as a function of time. The magnetic changes may have an amplitude of 20 to 50 nanoTeslas. If changes are more severe, as would occur from a magnetic storm, surveying is discontinued or the data recorded are not used.
Diurnal variations are then removed from the airborne magnetic data based on the common time.
Values of -9999.9 indicate missing data.

Attribute_Definition_Source:

see: Nettleton, L.L., 1971, Elementary Gravity and Magnetics for Geologists and Seismologists: Society of Exploration Geophysicists Monograph Series No. 1, p. 83-87.
A description of magnetometers and how they measure the total magnetic field can be found in:
Dobrin, M.B., 1976, Introduction to Geophysical Prospecting: New York, McGraw-Hill Book Company, p. 505-517.

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: 55968.00

Range_Domain_Maximum: 71192.00

Attribute_Units_of_Measure: nanoTeslas

Attribute_Value_Accuracy_Information:

Attribute_Value_Accuracy: 2

Attribute_Value_Accuracy_Explanation:

The airborne magnetometer is accurate to about 1 nanoTesla, and the base magnetometer has the same accuracy. The accuracy of the base-corrected airborne value therefore is near 2 nanoTeslas or better.

Attribute_Measurement_Frequency:

The magnetometer has a recharging interval of 0.5 seconds. The data were recorded at 2 second intervals.

Attribute:

Attribute_Label: resmag

Attribute_Definition:

residual magnetic value
The total magnetic value minus a geomagnetic reference field (GRF), which is a long-wavelength regional magnetic field. The most commonly used reference field is determined from a model developed by the International Association of Geomagnetism and Aeronomy (IAGA). The International Geomagnetic Reference Field (IGRF), is a predictive model adopted at the beginning of a model period (e.g. in 1989 for 1990-1995). After the model period, a revised definitive model is adopted, the DGRF. This is the preferred model to use for removing regional magnetic fields.
For this survey, the field removed was most likely the IGRF1965 calculated to the nearest tenth of a year. Whether or not the IGRF was removed was not mentioned in the contractor information.
Values of -9999.9 indicate missing data.

Attribute_Definition_Source:

Nettleton, L.L., 1971, Elementary Gravity and Magnetics for Geologists and Seismologists: Society of Exploration Geophysicists Monograph Series No. 1, p. 83-87.

Attribute_Domain_Values:

Range_Domain:

Range_Domain_Minimum: -1032.22

Range_Domain_Maximum: 14535.69

Attribute_Units_of_Measure: nanoTeslas

Attribute_Value_Accuracy_Information:

Attribute_Value_Accuracy: 2

Attribute_Value_Accuracy_Explanation:

The Geomagnetic Reference Field that was subtracted from the total magnetic value is based on a model, which was updated to the date of the survey. New models are available at five year intervals. These models have varying degrees of accuracy in determining the local reference field.

Distribution_Information:

Distributor:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: CD-ROM distributor: USGS Information Services

Contact_Address:

Address_Type: mailing address

Address:

Box 25286, Building 810
Denver Federal Center

City: Denver

State_or_Province: CO

Postal_Code: 80225

Contact_Voice_Telephone:

303-202-4700 or 1-888-ASK-USGS

Contact_Electronic_Mail_Address: www.usgs.gov/pubprod

Resource_Description: USGS Open-File Report OFR 02-0361

Distribution_Liability:

Although all data published on this CD-ROM 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
directn       I4
longitud      F11.4
latitude      F9.4
year          I5
jul_day       I4
fiducial      I7
radar         F8.1
barom         F8.1
totmag        F9.2
resmag        F9.2, 1X

Format_Information_Content: Magnetic anomaly measurements

File_Decompression_Technique: gunzip

Digital_Transfer_Option:

Offline_Option:

Offline_Media: CD-ROM

Recording_Format: ISO 9660

Fees:

CD-ROM prices are subject to change. Please call or see <http://mapping.usgs.gov/esic/prices/>

Ordering_Instructions:

Detailed instructions can be found at www.usgs.gov/pubprod

Distribution_Information:

Distributor:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization:

Web site administration: U.S Geological Survey Central Publications Group

Contact_Address:

Address_Type: mailing address

Address:

Central Publications Group
USGS MS 902, Box 25046 DFC

City: Denver

State_or_Province: CO

Postal_Code: 80225-0046

Contact_Voice_Telephone: 303-236-5486

Resource_Description: USGS Open-File Report OFR 02-0361

Distribution_Liability:

Although all data published on this CD-ROM 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
directn       I4
longitud      F11.4
latitude      F9.4
year          I5
jul_day       I4
fiducial      I7
radar         F8.1
barom         F8.1
totmag        F9.2
resmag        F9.2, 1X

Format_Information_Content: Magnetic anomaly measurements

File_Decompression_Technique: gunzip

Digital_Transfer_Option:

Online_Option:

Computer_Contact_Information:

Network_Address:

Network_Resource_Name:

<ftp://ftpmusette.cr.usgs.gov/pub/NA_MAGNETICS/digital_data/WY/WY_6001.xyz.gz>

Online_Computer_and_Operating_System:

Hewlett Packard 9000/K220 UNIX server running HPUX 11.00

Fees: none

Metadata_Reference_Information:

Metadata_Date: 20021112

Metadata_Contact:

Contact_Information:

Contact_Organization_Primary:

Contact_Organization: USGS Gravity and Magnetics contact

Contact_Address:

Address_Type: mailing address

Address:

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: 303-236-1343

Contact_Electronic_Mail_Address: grav_mag@usgs.gov

Metadata_Standard_Name: Content Standard for Digital Geospatial Metadata

Metadata_Standard_Version: FGDC-STD-001-1998