U.S. Geological Survey, Department of Interior and the National Geophysical Data Center, NOAA 2001 tabular digital data https://mrdata.usgs.gov/magnetic/show-survey.php?id=NV_4152 U.S. Geological Survey, Department of the Interior, and the National Geophysical Data Center 2001 U.S. Geological Survey Open-File Report OFR 02-0361 Denver, CO U.S. Geological Survey 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. 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. 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. 198811 198811 ground condition complete none planned -117.50 -117.80 41.38 40.88 -117.10 41.26, -117.23 41.11, -117.30 41.03, -117.27 41.02, -117.28 40.90, -117.32 40.88, -117.51 40.99, -117.23 41.33, -117.10 41.26 USGS Metadata Identifier USGS:4472a2fc-c672-4cea-8837-2f3c98c2d41d none geophysical surveys aeromagnetic data airborne surveys magnetic surveys residual magnetic field total field magnetic USGS Thesaurus geophysics geospatial datasets magnetic field (earth) aeromagnetic surveying field monitoring stations none United States Nevada NV Getchell Getchell Trend Humboldt County Common Geographic Areas f32013 = Humboldt none none. Acknowledgement of the U.S. Geological Survey and the National Geophysical Data Center would be appreciated in products derived from these data. USGS Gravity and Magnetics Contact mailing address

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

Denver CO 80225 303-236-1343 grav_mag@usgs.gov http://mrdata.usgs.gov/geophysics/surveys/geophysics2/NV/NV_4152.jpg Reduced-size image depicting the data, 550 x 620 pixels, 44,211 bytes JPEG 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 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. U.S. Geological Survey 1999 raster digital data U.S. Geological Survey Open-File Report OFR 99-557 Denver CO U.S. Geological Survey CD-ROM or online files Complements this publication with analog data http://pubs.usgs.gov/of/1999/ofr-99-0557/ U.S. Geological Survey 1990 map U.S. Geological Survey Open-File Report OFR 90-319 Denver, CO U.S. Geological Survey McConnell, D. L., with preface by Hoover, D.B., and Hill, P.L. map scale 1:24,000 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. 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. Loss of data due to poor transmission, channel dropout, obvious spiking, missing channels, and other obvious errors were replaced with the value -9999.9, such as radar, barom, and resmag channels. The original contractor database did not have flight line direction (directn), Julian day (jul_day), year (year), radar altimeter (radar), barometric altimeter (barom), or residual magnetics (resmag) channels. A dummy value of -1 was used in the directn channel in order to conform to the established template. A constant of 10,000 was subtracted from the line numbers in order to conform to the established template. The values in the fiducial channel were multiplied by 10 in order to conform to the established template. Line 11380 (converted line number 1380) is incomplete. Certain lines were extended beyond the survey boundaries in order to cover and tie into other surveys of additional areas of interest. Flight Path Recovery Horizontal position of the survey aircraft used to collect data were determined using aircraft navigational aids such as line-of-sight electronic systems that measure the distances from each of two ground stations to the aircraft using microwave or radio transmitters. 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 50 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 a average terrain clearance of 150 ft. Because aircraft, especially airplanes, cannot safely maintain a constant terrain clearance, error in vertical position is introduced. 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. 1988 USGS reformatting of contractor data to standard format. USGS personnel used the software package Oasis Montaj version 4.3 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. 200208 Added keywords section with USGS persistent identifier as theme keyword. 20201110 U.S. Geological Survey VeeAnn A. Cross Marine Geologist Mailing and Physical

384 Woods Hole Road

Woods Hole MA 02543-1598 508-548-8700 x2251 508-457-2310 vatnipp@usgs.gov point .0001 .0001 decimal degrees North American Datum of 1927 Clarke 1866 6,378,206.4 294.98 National Geodetic Vertical Datum of 1929 1 feet Explicit elevation coordinate included with horizontal coordinates Airborne survey specifications These items are constant for the entire survey Project number: 4152 Project name: Getchell EM, Nevada Survey flown by: DIGHEM Survey flown for: U.S. Geological Survey Approx. no. of line miles: 1150 Survey height: 150 ft Altitude method: Draped over terrain Flight-line spacing: 0.125-0.25 mi Flight-line direction: NW-SE (301 deg/121 deg) Aircraft used: Aerospatiale Lama 315B Airport - arrival: unknown Airport - departure: unknown Magnetometer used: Picodas cesium 3000 Sensor tow distance: 50 ft 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. 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) 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. record for one magnetic data point The set of all measurements reported for a magnetic data point having the same spatial location. Standard aeromagnetic data collection procedures as written in the contract for survey collection. line_no flight line number often assigned by airborne survey crew 10 9040 alphanumeric value directn direction of flight line, azimuth degrees clockwise from north self evident -1 -1 degrees longitud longitude - geographic coordinate self evident -117.4963 -117.0991 decimal degrees latitude latitude - geographic coordinate self evident 40.8787 41.3227 decimal degrees year year of data point collection self evident 1988 1988 jul_day Julian day, where Jan. 1 = 1 and Dec. 31 = 365 or 366 (leap year) self evident 306 306 31 The date was assigned based on the contractor report, USGS contract specifications and personnel experience. It was noted that the survey was run during November, 1988. The first day of November has been assigned by the USGS but not does necessarily reflect the actual date each line was flown. fiducial 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. Sheriff, R.E., 1984, Encyclopedic dictionary of exploration geophysics: Tulsa, OK, Society of Exploration Geophysicists, p. 89. 550 84554 radar 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. Sheriff, R.E., 1984, Encyclopedic dictionary of exploration geophysics: Tulsa, OK, Society of Exploration Geophysicists, p. 89. -9999.9 -9999.9 feet barom 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. self evident -9999.9 -9999.9 feet totmag 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. 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. 52358 58004 nanoTeslas 2 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. The magnetometer has a recharging interval of 0.5 seconds. The data were recorded at 0.1 second intervals. resmag 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 is unknown. Values of -9999.9 indicate missing data. Nettleton, L.L., 1971, Elementary Gravity and Magnetics for Geologists and Seismologists: Society of Exploration Geophysicists Monograph Series No. 1, p. 83-87. -9999.9 -9999.9 nanoTeslas 2 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. CD-ROM distributor: USGS Information Services mailing address

Box 25286, Building 810 Denver Federal Center

Denver CO 80225 303-202-4700 or 1-888-ASK-USGS www.usgs.gov/pubprod USGS Open-File Report OFR 02-0361 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. ASCII 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 gunzip CD-ROM ISO 9660 CD-ROM prices are subject to change. Please call or see http://mapping.usgs.gov/esic/prices/ Detailed instructions can be found at www.usgs.gov/pubprod Web site administration: U.S Geological Survey Central Publications Group mailing address

Central Publications Group USGS MS 902, Box 25046 DFC

Denver CO 80225-0046 303-236-5486 USGS Open-File Report OFR 02-0361 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. ASCII 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 gunzip 1.1 http://pubs.usgs.gov/of/2002/ofr-02-361/ Hewlett Packard 9000/K220 UNIX server running HPUX 11.00 none Peter N Schweitzer USGS Eastern Mineral and Environmental Resources Science Center Geologist mailing address

12201 Sunrise Valley Drive

Reston VA 20192-0002 USA 703-648-6533 703-648-6252 pschweitzer@usgs.gov NV_4152_meta.txt This dataset was prepared by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed in this report, or represents that its use would not infringe privately owned rights. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. Any views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. CSV Flight-line airborne magnetic anomaly measurements unzip 2.0672645568848 http://mrdata.usgs.gov/geophysics/surveys/geophysics2/NV/NV_4152.ZIP none 20201110 USGS Gravity and Magnetics contact mailing address

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

Denver CO 80225-0046 303-236-1343 grav_mag@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998