Southern Dishna River, Fox Hills, and Beaver Creek survey areas: Airborne Magnetic and electromagnetic data in line (point), grid, vector, and map formats, Iditarod, Ophir, and Holy Cross quadrangles, western Alaska

Frequently anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
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  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
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What does this data set describe?

1. How should this data set be cited?

   Burns, L.E., Fugro Airborne Surveys Corp., and Fugro GeoServices, Inc., 2013, Southern Dishna River, Fox Hills, and Beaver Creek survey areas: Airborne Magnetic and electromagnetic data in line (point), grid, vector, and map formats, Iditarod, Ophir, and Holy Cross quadrangles, western Alaska: Geophysical Report GPR 2013-1, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS), Fairbanks, AK, USA.

   Online Links:

   • <http://dx.doi.org/10.14509/26701>
   • <http://dggs.alaska.gov/pubs/gpdata/236>

   Other_Citation_Details: 1 DVD, scale 1:63,360.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -159.35

   East_Bounding_Coordinate: -156.89

   North_Bounding_Coordinate: 63.14

   South_Bounding_Coordinate: 62.14

3. What does it look like?

   gpr2013_001_browsegraphic.pdf (PDF)

   The browse graphic file contains three location maps showing 1) survey areas and adjacent published surveys within Alaska, 2) survey areas on 1:250,000 USGS quadrangles, and 3) boundaries of the map sheets.

4. Does the data set describe conditions during a particular time period?

   Beginning_Date: Sep-2012

   Ending_Date: Nov-2013

   Currentness_Reference: publication date

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form:

   raster digital data, tabular digital data, and vector digital data

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

   2. What coordinate system is used to represent geographic features?

      Grid_Coordinate_System_Name: Universal Transverse Mercator

      Universal_Transverse_Mercator:

      UTM_Zone_Number: 4

      Transverse_Mercator:

      Scale_Factor_at_Central_Meridian: 0.9996

      Longitude_of_Central_Meridian: -159

      Latitude_of_Projection_Origin: 0

      False_Easting: 500000

      False_Northing: 0

      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 25
      Ordinates (y-coordinates) are specified to the nearest 25
      Planar coordinates are specified in meters

      The horizontal datum used is North American Datum of 1927.
      The ellipsoid used is Clarke 1866.
      The semi-major axis of the ellipsoid used is 6378206.4.
      The flattening of the ellipsoid used is 1/294.978698.
      

7. How does the data set describe geographic features?

   SDishna_linedataAsGDB.zip and SDishna_linedataAsXYZ.zip

   The southern Dishna River files in the Linedata folder contain raw and processed linedata and related calculated fields for locational, magnetic, and electromagnetic data. The linedata files are provided in both Geosoft binary GDB and Geosoft ASCII XYZ formats; formatting varies slightly between these. Except for the 'LINE' and 'TYPE' (of line) information, all attributes, including 'DATE' and 'FLIGHT', are represented by one of the 50 data columns on each record. The 'LINE' and 'TYPE' attributes are discussed further in the attribute 'ID Cell'. (Source: L.E. Burns & Fugro Airborne Surveys)

   ID_CELL

   In the Geosoft software 'Oasis Montaj', information about the flight lines in the linedata file is shown in an unlabeled 'ID CELL' in the spreadsheet window. The format of the ID cell is 'TYPE LineNumber:Flight (Designator or Identifier), where TYPE refers to the type of flight line, LineNumber refers to the actual numbered line flown, and flight designator provides the data acquisition system identifier and the flight number. The 'ID CELL' content, particularly combined with the definitions below for this particular survey, provides information about the flight line layout. The 'Flight' designator is discussed below in more detail as an 'Attribute'. Each ID-cell value will have an associated spreadsheet view consisting of a column for each of the 50 attributes for a particular line number. In the XYZ file, the 'LINE' and 'FLIGHT' attributes and the 'DATE' are present as header lines, one attribute per line, before each set of associated data, for example:
   

     //Flight 3053
     //Date 2012/10/27
     Line 40010
     Followed by all records for points sampled along Line 40010.
        (Pattern is repeated for each line number).
   

   (Source: L.E. Burns & Fugro Airborne Surveys)

   LINE TYPES and SYMBOLS:

    Traverse lines - oriented nominally N20W (heading of 160 degrees)
    Tie lines      - oriented nominally N70E (heading of 70 degrees)
    Border lines   - present inside and parallel to the survey
                     tract border where traverse or tie lines
                     are not parallel to the border.
    Traverse lines - 'L' (GDB file); 'LINE' (XYZ file).
    Tie and border lines - 'T' (GDB file); 'TIE' (XYZ file).
   

   LINE NUMBERS

    Planned flight lines increase by 10 in a consistent fashion.
    For this project, traverse line numbers increase from SW to
    NE; tie line numbers increase from north to south; and
    border line numbers increase in a clockwise direction.
    When more than one uninterrupted flight traverse was needed
    to complete a planned flight line, the fifth digit of the line
    number is increased by '1' for each new flight segment/version.
     MAIN LINE NUMBERS:
                                    Dishna
    Lowest Traverse lines (SW):     L40010
    Highest Traverse lines (NE):    L41790
    Lowest Tie Lines:               T49010
    Highest Tie Lines:              T49110
    Lowest Border Lines:            T49121
    Highest Border Lines:           T49230
   

   x_NAD27z4N

   easting NAD 27 (UTM Zone 4) (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	554519.62
   Maximum:	608487.07
   Units:	m

   y_NAD27z4N

   northing NAD 27 (UTM Zone 4) (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	6935056.42
   Maximum:	7000987.44
   Units:	m

   fid

   Fiducial increment; the time in tenths of seconds from the start to the end of the particular flight. (Source: Fugro Airborne Surveys)

   The attribute measurement resolution is 0.1 second. The values increase from the beginning of a flight to the end. Only FIDs during production flights are included in the database.

   lat_WGS84

   latitude WGS 84 (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	62.5435090
   Maximum:	63.1237402
   Units:	degrees

   lon_WGS84

   longitude WGS 84 (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-157.9406338
   Maximum:	-156.8546699
   Units:	degrees

   flight

   The flight designator is composed of Fugro�s identification number of the HeliDAS (data acquisition system) used and the flight number. For the Southern Dishna block, three HeliDAS systems were used. The flight number, numbered sequentially for each helicopter, denotes a particular flight of that helicopter from home base to home base. Only flights that acquired final raw data for the survey are in the linedata files. (Source: Fugro Airborne Surveys)

   One helicopter (B-2) was used for the Dishna block. Helidas 13 was used for the first Dishna flight ('005') that acquired data. Helidas 3 acquired all remaining data for the Dishna survey. Values in the linedata channel for the Dishna survey include 13005, and an intermittent sequence from 3015 to 3054.

   date

   range of flight dates (yyyy/mm/dd) for production flights of the southern Dishna River survey (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	2012/09/15
   Maximum:	2012/10/28
   Units:	day

   altrad_calcbird

   calculated bird height above surface to simulate location of radar altimeter in the bird; radar altimeter measurement was recorded in helicopter. Altrad_calcbird was calculated by subtracting constant from which represented distance in altitude from helicopter to the bird when towing and recording data. (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	12.97
   Maximum:	112.62
   Units:	m

   altlas_bird

   bird height above surface, measured by laser altimeter in the EM bird (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	8.03
   Maximum:	116.43
   Units:	m

   gpsz

   bird height above spheroid. The GPSZ (or GPS-Z) value is primarily dependent on the number of available satellites. Although post-processing of GPS data will yield X and Y accuracies on the order of 1 meter, the accuracy of the Z value is usually much less, sometimes in the +/-20 meter range. (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	102.58
   Maximum:	777.20
   Units:	m

   dtm

   digital terrain model (NAD27 UTM zone 7); calculated from channel 'GPS-Z' and the laser data (channel 'ALTLAS_BIRD') measured in the bird (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	32.43
   Maximum:	721.05
   Units:	m

   diurnal_filt

   measured diurnal ground magnetic intensity; interpolated to 0.1 sec. from 1.0 second measurements (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	55468.28
   Maximum:	55819.14
   Units:	nT

   diurnal_cor

   diurnal correction - base removed; calculated from interpolated diurnal_filt (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-86.08
   Maximum:	138.91
   Units:	nT

   mag_raw

   total magnetic field - spike rejected (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	54303.22
   Maximum:	60885.57
   Units:	nT

   mag_lag

   total magnetic field - corrected for lag (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	54303.22
   Maximum:	60885.57
   Units:	nT

   mag_diu

   total magnetic field - diurnal variation removed (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	54343.65
   Maximum:	60881.77
   Units:	nT

   igrf

   international geomagnetic reference field (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	55606.03
   Maximum:	55862.19
   Units:	nT

   mag_rmi

   residual magnetic intensity - IGRF removed, then leveled - final (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-1432.81
   Maximum:	5102.29
   Units:	nT

   magigrf

   total magnetic field with IGRF removed - mag_rmi with constant added back - final (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	54292.09
   Maximum:	60821.19
   Units:	nT

   cpi900_FILT

   coplanar inphase 900 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-1007.05
   Maximum:	773.44
   Units:	ppm

   cpq900_FILT

   coplanar quadrature 900 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-12.75
   Maximum:	728.68
   Units:	ppm

   cxi1000_FILT

   coaxial inphase 1000 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-241.98
   Maximum:	208.21
   Units:	ppm

   cxq1000_FILT

   coaxial quadrature 1000 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-3.98
   Maximum:	184.01
   Units:	ppm

   cxi5500_FILT

   coaxial inphase 5500 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-209.99
   Maximum:	384.65
   Units:	ppm

   cxq5500_FILT

   coaxial quadrature 5500 Hz -unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-19.84
   Maximum:	260.49
   Units:	ppm

   cpi7200_FILT

   coplanar inphase 7200 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-760.45
   Maximum:	1421.43
   Units:	ppm

   cpq7200_FILT

   coplanar quadrature 7200 Hz -unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-39.46
   Maximum:	1101.60
   Units:	ppm

   cpi56K_FILT

   coplanar inphase 56 kHz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-556.54
   Maximum:	2120.97
   Units:	ppm

   cpq56K_FILT

   coplanar quadrature 56 kHz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-68.12
   Maximum:	3306.84
   Units:	ppm

   cpi900

   coplanar inphase 900 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-1006.94
   Maximum:	773.73
   Units:	ppm

   cpq900

   coplanar quadrature 900 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.32
   Maximum:	728.56
   Units:	ppm

   cxi1000

   coaxial inphase 1000 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-244.43
   Maximum:	206.60
   Units:	ppm

   cxq1000

   coaxial quadrature 1000 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-1.77
   Maximum:	184.40
   Units:	ppm

   cxi5500

   coaxial inphase 5500 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-213.27
   Maximum:	385.23
   Units:	ppm

   cxq5500

   coaxial quadrature 5500 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-6.07
   Maximum:	260.63
   Units:	ppm

   cpi7200

   coplanar inphase 7200 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-761.23
   Maximum:	1421.56
   Units:	ppm

   cpq7200

   coplanar quadrature 7200 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	4.72
   Maximum:	1101.58
   Units:	ppm

   cpi56k

   coplanar inphase 56k Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-561.87
   Maximum:	2121.18
   Units:	ppm

   cpq56K

   coplanar quadrature 56k Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	12.35
   Maximum:	3306.77
   Units:	ppm

   res900

   apparent resistivity 900 Hz; cut-off value for apparent resistivity was 1325; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.30
   Maximum:	1325
   Units:	ohm�m

   res7200

   apparent resistivity 7200 Hz; cut-off value for apparent resistivity was 10750; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	1.67
   Maximum:	10750
   Units:	ohm�m

   res56K

   apparent resistivity 56k Hz; cut-off value for apparent resistivity was 60000; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	7.01
   Maximum:	15710.22
   Units:	ohm�m

   dep900

   apparent depth 900 Hz; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-72.51
   Maximum:	319.96
   Units:	m

   dep7200

   apparent depth 7200 Hz; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-57.42
   Maximum:	70.74
   Units:	m

   dep56K

   apparent depth 56k Hz; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-45.56
   Maximum:	19.94
   Units:	m

   difi

   difference channel based on cxi5500 & cpi7200 (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-64.00
   Maximum:	104.15
   Units:	unitless

   difq

   difference channel based on cxq5500 & cpq7200 (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-45.19
   Maximum:	105.26
   Units:	unitless

   cppl

   coplanar powerline monitor (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.00
   Maximum:	1.52
   Units:	unitless

   cxsp

   coaxial spherics monitor (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.00
   Maximum:	0.04
   Units:	unitless

   cpsp

   coplanar spherics monitor (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.00
   Maximum:	0.23
   Units:	unitless

   FoxHills_linedata_asGDB.zip and Fox Hills_linedata_asXYZ.zip

   The Fox Hills files in the Linedata folder contain raw and processed linedata and related calculated fields for locational, magnetic, and electromagnetic data. Linedata is provided in Geosoft binary grid (GRD) and Geosoft ASCII XYZ (XYZ) formats; formatting varies slightly between these. Except for the 'LINE' and 'TYPE' (of line) information, all attributes, including 'DATE' and 'FLIGHT', are represented by one of the 50 data columns on each record. The 'LINE' and 'TYPE' attributes are discussed further in the attribute 'ID Cell'. (Source: L.E. Burns & Fugro Airborne Surveys)

   ID_CELL

   In the Geosoft software 'Oasis Montaj', information about the flight lines in the linedata file is shown in an unlabeled 'ID CELL' in the spreadsheet window. The format of the ID cell is 'TYPE LineNumber:Flight (Designator or Identifier), where TYPE refers to the type of flight line, LineNumber refers to the actual numbered line flown, and flight designator provides the data acquisition system identifier and the flight number. The 'ID CELL' content, particularly combined with the definitions below for this particular survey, provides information about the flight line layout. The 'Flight' designator is discussed below in more detail as an 'Attribute'. Each ID-cell value will have an associated spreadsheet view consisting of a column for each of the 50 attributes for a particular line number. In the XYZ file, the 'LINE' and 'FLIGHT' attributes and the 'DATE' are present as header lines, one attribute per line, before each set of associated data, for example:

   
     //Flight 4094
     //Date 2012/10/24
     Line 60010
     Followed by all records for points sampled along Line 60010.
        (Pattern is repeated for each line number).
   

   (Source: L.E. Burns & Fugro Airborne Surveys)

   LINE TYPES and SYMBOLS:

    Traverse lines � oriented nominally N20W (heading of 160 degrees)
    Tie lines      - oriented nominally N70E (heading of 70 degrees)
    Border lines   - present inside and parallel to the survey
                     tract border where traverse or tie lines
                     are not parallel to the border.
    Traverse lines � 'L' (GDB file); 'LINE' (XYZ file).
    Tie and border lines - 'T' (GDB file); 'TIE' (XYZ file).
   

   LINE NUMBERS

    Planned flight lines increase by 10 in a consistent fashion.
    For this project, traverse line numbers increase from SW to
    NE; tie line numbers increase from north to south; and
    border line numbers increase in a clockwise direction.
   
    When more than one uninterrupted flight traverse was needed
    to complete a planned flight line, the fifth digit of the line
    number is increased by '1' for each new flight segment/version.
   

   MAIN LINE NUMBERS:

                                   FoxHills
    Lowest Traverse lines(SW):     L60010
    Highest Traverse lines(NE):    L61000
    Lowest Tie Lines:              T69010
    Highest Tie Lines:             T69050
    Lowest Border Lines:           T69060
    Highest Border Lines:          T69160
   

   x_NAD27z4N

   easting NAD 27 (UTM Zone 4) (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	481681.92
   Maximum:	521307.60
   Units:	m

   y_NAD27z4N

   northing NAD 27 (UTM Zone 4) (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	6889631.32
   Maximum:	6907110.22
   Units:	m

   fid

   Fiducial increment; the time in tenths of seconds from the start to the end of the particular flight. (Source: Fugro Airborne Surveys)

   The attribute measurement resolution is 0.1 second. The values increase from the beginning of a flight to the end. Only FIDs during production flights are included in the database.

   lat_WGS84

   latitude WGS 84 (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	62.1397998
   Maximum:	62.2961265
   Units:	degrees

   lon_WGS84

   longitude WGS 84 (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-159.3545631
   Maximum:	-158.5917447
   Units:	degrees

   flight

   The flight designator is composed of Fugro�s identification number of the HeliDAS (data acquisition system) used and the flight number. For the Fox Hills block, one helicopter using HeliDAS '4' was the only one used. Only flights that acquired final raw data for the survey are in the linedata files. (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	4090
   Maximum:	4098
   Units:	flight

   date

   range of flight dates (yyyy/mm/dd) for production flights (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	2012/10/24
   Maximum:	2012/10/27
   Units:	day

   altrad_calcbird

   calculated bird height above surface to simulate location of radar altimeter in the bird; radar altimeter measurement was recorded in helicopter. Altrad_calcbird was calculated by subtracting constant from which represented distance in altitude from helicopter to the bird when towing and recording data. (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	22.59
   Maximum:	78.55
   Units:	m

   altlas_bird

   bird height above surface, measured by laser altimeter in the EM bird (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	21.13
   Maximum:	78.42
   Units:	m

   gpsz

   bird height above spheroid. The GPSZ (or GPS-Z) value is primarily dependent on the number of available satellites. Although post-processing of GPS data will yield X and Y accuracies on the order of 1 meter, the accuracy of the Z value is usually much less, sometimes in the +/-20 meter range. (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	60.50
   Maximum:	602.35
   Units:	m

   dtm

   digital terrain model (NAD27 UTM zone 4); calculated from channel 'GPS-Z' and the laser data (channel 'ALTLAS_BIRD') measured in the bird ' (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	26.48
   Maximum:	562.93
   Units:	m

   diurnal_filt

   measured diurnal ground magnetic intensity; interpolated to 0.1 sec. from 1.0 second measurements (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	55582.01
   Maximum:	55597.00
   Units:	nT

   diurnal_cor

   diurnal correction - base removed; calculated from interpolated diurnal_filt (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-10.59
   Maximum:	4.40
   Units:	nT

   mag_raw

   total magnetic field - spike rejected (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	52388.49
   Maximum:	57441.22
   Units:	nT

   mag_lag

   total magnetic field - corrected for lag (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	52388.49
   Maximum:	57441.22
   Units:	nT

   mag_diu

   total magnetic field - diurnal variation removed (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	52392.67
   Maximum:	57445.93
   Units:	nT

   igrf

   international geomagnetic reference field (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	55388.72
   Maximum:	55473.76
   Units:	nT

   mag_rmi

   residual magnetic intensity - IGRF removed, then leveled - final (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-3062.14
   Maximum:	1976.96
   Units:	nT

   magigrf

   total magnetic field with IGRF removed - mag_rmi with constant added back - final (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	52362.96
   Maximum:	57401.53
   Units:	nT

   cpi900_FILT

   coplanar inphase 900 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-96.11
   Maximum:	717.82
   Units:	ppm

   cpq900_FILT

   coplanar quadrature 900 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.61
   Maximum:	541.30
   Units:	ppm

   cxi1000_FILT

   coaxial inphase 1000 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-27.54
   Maximum:	142.87
   Units:	ppm

   cxq1000_FILT

   coaxial quadrature 1000 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-4.97
   Maximum:	156.90
   Units:	ppm

   cxi5500_FILT

   coaxial inphase 5500 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-27.67
   Maximum:	308.49
   Units:	ppm

   cxq5500_FILT

   coaxial quadrature 5500 Hz -unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-0.37
   Maximum:	238.31
   Units:	ppm

   cpi7200_FILT

   coplanar inphase 7200 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-59.83
   Maximum:	1054.10
   Units:	ppm

   cpq7200_FILT

   coplanar quadrature 7200 Hz -unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	6.33
   Maximum:	825.07
   Units:	ppm

   cpi56K_FILT

   coplanar inphase 56 kHz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-25.12
   Maximum:	1728.81
   Units:	ppm

   cpq56K_FILT

   coplanar quadrature 56 kHz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	37.49
   Maximum:	789.37
   Units:	ppm

   cpi900

   coplanar inphase 900 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-99.26
   Maximum:	713.56
   Units:	ppm

   cpq900

   coplanar quadrature 900 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.07
   Maximum:	541.71
   Units:	ppm

   cxi1000

   coaxial inphase 1000 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-30.19
   Maximum:	142.91
   Units:	ppm

   cxq1000

   coaxial quadrature 1000 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-4.44
   Maximum:	157.01
   Units:	ppm

   cxi5500

   coaxial inphase 5500 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-27.22
   Maximum:	308.22
   Units:	ppm

   cxq5500

   coaxial quadrature 5500 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	1.41
   Maximum:	244.19
   Units:	ppm

   cpi7200

   coplanar inphase 7200 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-59.97
   Maximum:	1054.05
   Units:	ppm

   cpq7200

   coplanar quadrature 7200 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	6.82
   Maximum:	833.54
   Units:	ppm

   cpi56k

   coplanar inphase 56k Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-25.34
   Maximum:	1728.84
   Units:	ppm

   cpq56K

   coplanar quadrature 56k Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	37.48
   Maximum:	790.30
   Units:	ppm

   res900

   apparent resistivity 900 Hz; cut-off value for apparent resistivity was 1325; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.06
   Maximum:	1325
   Units:	ohm�m

   res7200

   apparent resistivity 7200 Hz; cut-off value for apparent resistivity was 10750; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.83
   Maximum:	8632.46
   Units:	ohm�m

   res56K

   apparent resistivity 56k Hz; cut-off value for apparent resistivity was 60000; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	10.87
   Maximum:	18100.85
   Units:	ohm�m

   dep900

   apparent depth 900 Hz; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-35.08
   Maximum:	111.80
   Units:	m

   dep7200

   apparent depth 7200 Hz; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-38.48
   Maximum:	71.26
   Units:	m

   dep56K

   apparent depth 56k Hz; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-32.37
   Maximum:	31.59
   Units:	m

   difi

   difference channel based on cxi5500 & cpi7200 (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-34.19
   Maximum:	78.54
   Units:	unitless

   difq

   difference channel based on cxq5500 & cpq7200 (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-6.75
   Maximum:	53.17
   Units:	unitless

   cppl

   coplanar powerline monitor (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.00
   Maximum:	0.00
   Units:	unitless

   cxsp

   coaxial spherics monitor (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.00
   Maximum:	0.00
   Units:	unitless

   cpsp

   coplanar spherics monitor (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.00
   Maximum:	0.00
   Units:	unitless

   BeaverCrk_linedata_asGDB.zip and BeaverCrk_linedata_asXYZ.zip

   The Beaver Creek files in the Linedata folder contain raw and processed linedata and related calculated fields for locational, magnetic, and electromagnetic data. Linedata is provided in Geosoft binary grid (GRD) and Geosoft ASCII XYZ (XYZ) formats; formatting varies slightly between these. Except for the 'LINE' and 'TYPE' (of line) information, all attributes, including 'DATE' and 'FLIGHT', are represented by one of the 50 data columns on each record. The 'LINE' and 'TYPE' attributes are discussed further in the attribute 'ID Cell'. (Source: L.E. Burns & Fugro Airborne Surveys)

   ID_CELL

   In the Geosoft software 'Oasis Montaj', information about the flight lines in the linedata file is shown in an unlabeled 'ID CELL' in the spreadsheet window. The format of the ID cell is 'TYPE LineNumber:Flight (Designator or Identifier), where TYPE refers to the type of flight line, LineNumber refers to the actual numbered line flown, and flight designator provides the data acquisition system identifier and the flight number. The 'ID CELL' content, particularly combined with the definitions below for this particular survey, provides information about the flight line layout. The 'Flight' designator is discussed below in more detail as an 'Attribute'. Each ID-cell value will have an associated spreadsheet view consisting of a column for each of the 50 attributes for a particular line number. In the XYZ file, the 'LINE' and 'FLIGHT' attributes and the 'DATE' are present as header lines, one attribute per line, before each set of associated data, for example:

   
     //Flight 3054
     //Date 2012/10/28
     Line 50010
     Followed by all records for points sampled along Line 10010.
        (Pattern is repeated for each line number).
   

   (Source: L.E. Burns & Fugro Airborne Surveys)

   LINE TYPES and SYMBOLS:

    Traverse lines � oriented nominally N20W (heading of 160 degrees)
    Tie lines      - oriented nominally N70E (heading of 70 degrees)
    Border lines   - present inside and parallel to the survey
                     tract border where traverse or tie lines
                     are not parallel to the border.
    Traverse lines � 'L' (GDB file); 'LINE' (XYZ file).
    Tie and border lines - 'T' (GDB file); 'TIE' (XYZ file).
   
    LINE NUMBERS
    Planned flight lines increase by 10 in a consistent fashion.
    For this project, traverse line numbers increase from SW to
    NE; tie line numbers increase from north to south; and
    border line numbers increase in a clockwise direction.
   
    When more than one uninterrupted flight traverse was needed
    to complete a planned flight line, the fifth digit of the line
    number is increased by '1' for each new flight segment/version.
   
     MAIN LINE NUMBERS:
                                   BeaverCk
    Lowest Traverse lines(SW):     L50010
    Highest Traverse lines(NE):    L50770
    Lowest Tie Lines:              T59010
    Highest Tie Lines:             T59060
    Lowest Border Lines:           T59070
    Highest Border Lines:          T59170
   

   x_NAD27z4N

   easting NAD 27 (UTM Zone 4) (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	566615.37
   Maximum:	595794.27
   Units:	m

   y_NAD27z4N

   northing NAD 27 (UTM Zone 4) (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	6902855.96
   Maximum:	6933910.75
   Units:	m

   fid

   Fiducial increment; the time in tenths of seconds from the start to the end of the particular flight. (Source: Fugro Airborne Surveys)

   The attribute measurement resolution is 0.1 second. The values increase from the beginning of a flight to the end. Only FIDs during production flights are included in the database.

   lat_WGS84

   latitude WGS 84 (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	62.2483707
   Maximum:	62.5271700
   Units:	degrees

   lon_WGS84

   longitude WGS 84 (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-157.7107234
   Maximum:	-157.1501231
   Units:	degrees

   flight

   The flight designator is composed of Fugro�s identification number of the HeliDAS (data acquisition system) used and the flight number. For the Beaver Creek block, two HeliDAS systems were used. The flight number, numbered sequentially for each helicopter, denotes a particular flight of that helicopter from home base to home base. Only flights that acquired final raw data for the survey are in the linedata files. (Source: Fugro Airborne Surveys)

   Two helicopters (B-2) were used for the Beaver Creek block. Values in the linedata channel for the this survey include flights between 3054 to 3065, and 4099 to 4102.

   date

   range of flight dates (yyyy/mm/dd) for production flights (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	2012/10/28
   Maximum:	2012/11/02
   Units:	day

   altrad_calcbird

   calculated bird height above surface to simulate location of radar altimeter in the bird; radar altimeter measurement was recorded in helicopter. Altrad_calcbird was calculated by subtracting constant from which represented distance in altitude from helicopter to the bird when towing and recording data. (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	11.54
   Maximum:	121.94
   Units:	m

   altlas_bird

   bird height above surface, measured by laser altimeter in the EM bird (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	9.34
   Maximum:	123.06
   Units:	m

   gpsz

   bird height above spheroid. The GPSZ (or GPS-Z) value is primarily dependent on the number of available satellites. Although post-processing of GPS data will yield X and Y accuracies on the order of 1 meter, the accuracy of the Z value is usually much less, sometimes in the +/-20 meter range. (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	154.90
   Maximum:	707.10
   Units:	m

   dtm

   digital terrain model (NAD27 UTM zone 7); calculated from channel 'GPS-Z' and the laser data (channel 'ALTLAS_BIRD') measured in the bird ' (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	123.65
   Maximum:	669.09
   Units:	m

   diurnal_filt

   measured diurnal ground magnetic intensity; interpolated to 0.1 sec. from 1.0 second measurements (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	55319.37
   Maximum:	55484.44
   Units:	nT

   diurnal_cor

   diurnal correction - base removed; calculated from interpolated diurnal_filt (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-165.03
   Maximum:	4.33
   Units:	nT

   mag_raw

   total magnetic field - spike rejected (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	55296.18
   Maximum:	55595.92
   Units:	nT

   mag_lag

   total magnetic field - corrected for lag (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	55296.18
   Maximum:	55595.92
   Units:	nT

   mag_diu

   total magnetic field - diurnal variation removed (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	55367.04
   Maximum:	55602.24
   Units:	nT

   igrf

   international geomagnetic reference field (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	55529.13
   Maximum:	55636.07
   Units:	nT

   mag_rmi

   residual magnetic intensity - IGRF removed, then leveled - final (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-214.90
   Maximum:	8.87
   Units:	nT

   magigrf

   total magnetic field with IGRF removed - mag_rmi with constant added back - final (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	55367.23
   Maximum:	55586.87
   Units:	nT

   cpi900_FILT

   coplanar inphase 900 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-17.35
   Maximum:	57.28
   Units:	ppm

   cpq900_FILT

   coplanar quadrature 900 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	2.86
   Maximum:	202.54
   Units:	ppm

   cxi1000_FILT

   coaxial inphase 1000 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-4.95
   Maximum:	21.45
   Units:	ppm

   cxq1000_FILT

   coaxial quadrature 1000 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-0.4
   Maximum:	65.88
   Units:	ppm

   cxi5500_FILT

   coaxial inphase 5500 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-9.77
   Maximum:	103.41
   Units:	ppm

   cxq5500_FILT

   coaxial quadrature 5500 Hz -unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-8.91
   Maximum:	175.77
   Units:	ppm

   cpi7200_FILT

   coplanar inphase 7200 Hz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-0.84
   Maximum:	376.97
   Units:	ppm

   cpq7200_FILT

   coplanar quadrature 7200 Hz -unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	11.35
   Maximum:	772.03
   Units:	ppm

   cpi56K_FILT

   coplanar inphase 56 kHz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	22.84
   Maximum:	1324.05
   Units:	ppm

   cpq56K_FILT

   coplanar quadrature 56 kHz - unlevelled (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	11.17
   Maximum:	3429.34
   Units:	ppm

   cpi900

   coplanar inphase 900 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-13.12
   Maximum:	54.91
   Units:	ppm

   cpq900

   coplanar quadrature 900 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	2.69
   Maximum:	202.36
   Units:	ppm

   cxi1500

   coaxial inphase 1000 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-3.53
   Maximum:	20.4
   Units:	ppm

   cxq1500

   coaxial quadrature 1000 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-0.41
   Maximum:	65.97
   Units:	ppm

   cxi5500

   coaxial inphase 5500 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-0.84
   Maximum:	103.59
   Units:	ppm

   cxq5500

   coaxial quadrature 5500 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	2.75
   Maximum:	175.74
   Units:	ppm

   cpi7200

   coplanar inphase 7200 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.45
   Maximum:	377.12
   Units:	ppm

   cpq7200

   coplanar quadrature 7200 Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	10.73
   Maximum:	771.97
   Units:	ppm

   cpi56k

   coplanar inphase 56k Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	23.12
   Maximum:	1324.38
   Units:	ppm

   cpq56K

   coplanar quadrature 56k Hz (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	10.60
   Maximum:	3428.81
   Units:	ppm

   res900

   apparent resistivity 900 Hz; cut-off value for apparent resistivity was 1325; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	47.81
   Maximum:	1325
   Units:	ohm�m

   res7200

   apparent resistivity 7200 Hz; cut-off value for apparent resistivity was 10750; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	45.14
   Maximum:	5347.72
   Units:	ohm�m

   res56K

   apparent resistivity 56k Hz; cut-off value for apparent resistivity was 60000; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	35.94
   Maximum:	2272.85
   Units:	ohm�m

   dep900

   apparent depth 900 Hz; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-56.58
   Maximum:	117.79
   Units:	m

   dep7200

   apparent depth 7200 Hz; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-35.21
   Maximum:	30.59
   Units:	m

   dep56K

   apparent depth 56k Hz; more information in process steps (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-35.12
   Maximum:	10.77
   Units:	m

   difi

   difference channel based on cxi5500 & cpi7200 (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-16.22
   Maximum:	31.01
   Units:	unitless

   difq

   difference channel based on cxq5500 & cpq7200 (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	-29.42
   Maximum:	51.92
   Units:	unitless

   cppl

   coplanar powerline monitor (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.00
   Maximum:	1.48
   Units:	unitless

   cxsp

   coaxial spherics monitor (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.00
   Maximum:	0.04
   Units:	unitless

   cpsp

   coplanar spherics monitor (Source: Fugro Airborne Surveys)

   Range of values
   Minimum:	0.00
   Maximum:	0.21
   Units:	unitless

   gpr2013-1_GRIDSasGRD_NAD27_z4N.zip and gpr2013-1_GRIDSasERS_NAD27_z4N.zip are included in gpr2013-1_GRIDS_as_ERS-and-GRD.zip in the online version

   The zip files contain the 30 grids and supporting files for this publication in either Geosoft binary float (GRD) format and/or ER Mapper (ERS) format. Each grid is in NAD27 datum, UTM Zone 4N, and has a 25m cell size with x and y in meters. An image from each of the grids is provided as Geotiffs and KMZ files. Grid files are listed below as attributes.

   The Geosoft grid consists of one file (.GRD). Each ER Mapper grid consists of two files, a header (projection) file (.ERS) and a data file (no extension). Both ER Mapper files are necessary to view a grid or to convert it to another software format. In addition, Geosoft projection files (GI) are included for both Geosoft and ER Mapper grids files, which automatically sets the projection of the grid in the associated software if the appropriate GI file is placed in the same directory as the grid.

   Each ER Mapper grid consists of two files, a header (projection) file (.ERS) and a data file (no extension). Both ER Mapper files are necessary to view a grid or to convert it to another software format. (Source: Fugro Airborne Surveys)

   XXX_magRMI

   Residual magnetic field (nT) - final; IGRF model 2010, updated for date of flight and elevation variations, was subtracted from Mag_Diu, then the data were leveled. (Source: Fugro Airborne Surveys)

   Grid file

   XXX_magIGRF

   Total magnetic field (nT) - final, with IGRF removed; residual magnetic field (magRMI) with constant added back in. Not produced as a map. (Source: Fugro Airborne Surveys)

   Grid file

   XXX_1VD

   First vertical derivative 'dz' (nT/m) of the total magnetic field with IGRF removed; also referred to as 'calculated vertical gradient' (cvg). (Source: Fugro Airborne Surveys)

   Grid file

   XXX_ASig

   Analytic signal (nT/m) calculated from the total magnetic field with IGRF removed. (Source: Fugro Airborne Surveys)

   Grid file

   XXX_TiltDer

   Tilt derivative (degrees) of the total magnetic field with IGRF removed. (Source: Fugro Airborne Surveys)

   Grid file

   XXX_res56k

   Apparent coplanar resistivity (ohm-m) for 56,000 (56k) Hz.; calculated using a pseudo-layer half-space model. (Source: Fugro Airborne Surveys)

   Grid file

   XXX_res7200

   Apparent coplanar resistivity (ohm-m) for 7200 Hz.; calculated using a pseudo-layer half-space model. (Source: Fugro Airborne Surveys)

   Grid file

   XXX_res900

   Apparent coplanar resistivity (ohm-m) for 900 Hz.; calculated using a pseudo-layer half-space model. (Source: Fugro Airborne Surveys)

   Grid file

   XXX_DTM

   Digital terrain or elevation model (m). Not shown as a map. (Source: Fugro Airborne Surveys)

   Grid file

   XXX_AltLasBird

   EM bird height (m) above surface, measured by Laser altimeter in EM bird. Not shown as a map. (Source: Fugro Airborne Surveys)

   Grid file

   gpr2013-1_GEOTIFFS_NAD27_z4N.zip

   The zip file 'GPR2013-1_GEOTIFGS_NAD27_z4N.zip' contains GeoTiffs in NAD27, UTM Zone 4N. Each of the 11 grids is represented in GeoTiff (TIF) format. Each of the 10 grids for each area is provided as a GeoTiff file. For each area, the images shown in 7 of the KMZ files are the same images used on the maps in this publication; no maps were made of the other 3 images. (Source: Fugro Airborne Surveys)

   XXX_magRMI

   Residual magnetic field (nT) - final; IGRF model 2010, updated for date of flight and elevation variations, was subtracted from Mag_Diu, then the data were leveled. (Source: Fugro Airborne Surveys)

   Geotiff file

   XXX_magIGRF

   Total magnetic field (nT) - final, with IGRF removed; residual magnetic field (magRMI) with constant added back in. Not produced as a map. (Source: Fugro Airborne Surveys)

   Geotiff file

   XXX_1VD

   First vertical derivative 'dz' (nT/m) of the total magnetic field with IGRF removed; also referred to as 'calculated vertical gradient' (cvg). (Source: Fugro Airborne Surveys)

   Geotiff file

   XXX_ASig

   Analytic signal (nT/m) calculated from the total magnetic field with IGRF removed. (Source: Fugro Airborne Surveys)

   Geotiff file

   XXX_TiltDer

   Tilt derivative (degrees) of the total magnetic field with IGRF removed. (Source: Fugro Airborne Surveys)

   Geotiff file

   XXX_res56k

   Apparent coplanar resistivity (ohm-m) for 56,000 (56k) Hz.; calculated using a pseudo-layer half-space model. (Source: Fugro Airborne Surveys)

   Geotiff file

   XXX_res7200

   Apparent coplanar resistivity (ohm-m) for 7200 Hz.; calculated using a pseudo-layer half-space model. (Source: Fugro Airborne Surveys)

   Geotiff file

   XXX_res900

   Apparent coplanar resistivity (ohm-m) for 900 Hz.; calculated using a pseudo-layer half-space model. (Source: Fugro Airborne Surveys)

   Geotiff file

   XXX_DTM

   Digital terrain or elevation model (m). Not shown as a map. (Source: Fugro Airborne Surveys)

   Geotiff file

   Lad_AltLasBird

   EM bird height (m) above surface, measured by Laser altimeter in EM bird. Not shown as a map. (Source: Fugro Airborne Surveys)

   Geotiff file

   gpr2013-1_KMZS_WGS84.zip

   The zip file 'gpr2013-1_KMZS_WGS84.zip' contains Google Earth KMZ files in Geographic Coordinate System (Simple Cylindrical projection) with a WGS84 datum. Each of the 10 grids for each area is provided as a kmz file. For each area, the images shown in 7 of the KMZ files are the same images used on the maps in this publication; no maps were made of the other 3 images. (Source: Fugro Airborne Surveys)

   XXX_magRMI

   Residual magnetic field (nT) - final; IGRF model 2010, updated for date of flight and elevation variations, was subtracted from Mag_Diu, then the data were leveled. (Source: Fugro Airborne Surveys)

   KMZ file

   XXX_magIGRF

   Total magnetic field (nT) - final, with IGRF removed; residual magnetic field (magRMI) with constant added back in. Not produced as a map. (Source: Fugro Airborne Surveys)

   KMZ file

   XXX_1VD

   First vertical derivative 'dz' (nT/m) of the total magnetic field with IGRF removed; also referred to as 'calculated vertical gradient' (cvg). (Source: Fugro Airborne Surveys)

   KMZ file

   XXX_ASig

   Analytic signal (nT/m) calculated from the total magnetic field with IGRF removed. (Source: Fugro Airborne Surveys)

   KMZ file

   XXX_TiltDer

   Tilt derivative (degrees) of the total magnetic field with IGRF removed. (Source: Fugro Airborne Surveys)

   KMZ file

   XXX_res56k

   Apparent coplanar resistivity (ohm-m) for 56,000 (56k) Hz.; calculated using a pseudo-layer half-space model. (Source: Fugro Airborne Surveys)

   KMZ file

   XXX_res7200

   Apparent coplanar resistivity (ohm-m) for 7200 Hz.; calculated using a pseudo-layer half-space model. (Source: Fugro Airborne Surveys)

   KMZ file

   XXX_res900

   Apparent coplanar resistivity (ohm-m) for 900 Hz.; calculated using a pseudo-layer half-space model. (Source: Fugro Airborne Surveys)

   KMZ file

   XXX_DTM

   Digital terrain or elevation model (m). Not shown as a map. (Source: Fugro Airborne Surveys)

   KMZ file

   gpr2013-1_VECTORSasDXF_NAD27_z4N and gpr2013-1_VECTORSasSHP_NAD27_z4N

   Data contours produced for the maps are provided in Autocad DXF and ESRI shape file format. Except for maps GPR2013-1-6 and GPR2013-1-7, the vector files are shown on the maps without topography. Caution should be used when reading the contour labels from the shape and DXF files as they may appear to be with a different line. Additional vector files included are the flight path, the Alaska Section Grid, and a UTM grid for each map or survey area.

    Each file format (DXF and shape file) contains the same information. A DXF file (e.g. XXX_magRMI.dxf) contains the information in layers within the file, and the shape file format consists of each layer as a separate file (e.g. XXX_magRMI_1, XXX_magRMI_2, XXX_magRMI_3, and XXX_magRMI_4). Most sets of shape files in this publication contain 4 or 5 files. Each type of contours is only described once in the 'Attribute' items below. Please refer to the map legends for appropriate line widths and particular label placement.
    Neither the DXF nor the shape files are attributed. All labeling is done through individual non-text characters, e.g. line number 60010 would be represented by 5 individual characters instead of one number. Sometimes the numbers or letters are formed from disconnected lines and/or arcs.
   

   (Source: Fugro Airborne Surveys)

   XXX_magRMI

   Contours, "triangles" denoting lows, and labels for the residual magnetic field data (Source: Fugro Airborne Surveys)

   vector file

   XXX_ASig

   Contours and labels for the analytic signal data (Source: Fugro Airborne Surveys)

   vector file

   XXX_TiltDer

   Contours and labels for the magnetic tilt derivative data Contours are provided at specific values for aid in interpretation of approximate contact location '0' contour), and depth to contact. Contours include the values -45, -30, -15, 0, +15, +30, and +45. (Source: Fugro Airborne Surveys)

   vector file

   XXX_res56k

   Contours and labels for the 56,000 Hz coplanar apparent resistivity data (Source: Fugro Airborne Surveys)

   vector file

   XXX_res7200

   Contours and labels for the 7200 Hz coplanar apparent resistivity data (Source: Fugro Airborne Surveys)

   vector file

   XXX_res900

   Contours and labels for the 900 Hz coplanar apparent resistivity data (Source: Fugro Airborne Surveys)

   vector file

   XXX_FP

   Flight, tie, and border lines, line and flight numbers, tics and labels for the survey lines flown; file not attributed (Source: Fugro Airborne Surveys)

   a continuous line is used for each flight line; short tics are used for 10 second fiducial marks; larger tics are used for 50 second fiducial marks; 'numbers' for the line numbers, flight numbers, and tics are non-editable text. The end of a flight line that is labeled with both the line number and the flight number, instead of just the line number, is the indicator for the start of the flight.

   XXX_SecGrid

   Alaska PLSS Section Grid (original file name 'pls_section') for the map areas. Modified by Fugro Airborne Surveys for line width, color, township and range numbers, and latitude and longitude to use on the maps. (Source: Alaska Department of Natural Resources - Land Records Information Section; L.E. Burns, Division of Geological & Geophysical Surveys; and Fugro Airborne Surveys)

   vector file

   XXX_UTMGrid

   A UTM grid for the map area produced by Fugro Airborne Surveys. Consists of non-text UTM labels around the edges of the map sheets. (Source: Fugro Airborne Surveys)

   vector file

   gpr2013-1_01-39_ALL_HPGL2.zip, gpr2013-1_MAPS_01-13_Dishna_PDFS, gpr2013-1_MAPS_14-39_FoxBeaver_PDFSDish.zip

   Zip file names indicate the map numbers and format included in the zip file. Dishna maps are numbered '1A', '1B', etc., to '13A' and '13B'. Maps for Fox Hills are numbered 14-26, and the Beaver Creek maps are numbered 27-39. (Source: Fugro Airborne Surveys)

   GPR2013-1-1A

   Residual magnetic field with topography; in nanoteslas (nT); northern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-1B

   Residual magnetic field with topography; in nanoteslas (nT); southern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-2A

   Residual magnetic field with data contours; in nanoteslas (nT); northern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-2B

   Residual magnetic field (nT) with data contours; in nanoteslas (nT); southern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-3A

   First vertical derivative with topography; in nT/m; calculated from the residual magnetic field; northern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-3B

   First vertical derivative with topography; in nT/m; calculated from the residual magnetic field; southern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-4A

   Analytic signal with topography; in nT/m; calculated from the residual magnetic field; northern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-4B

   Analytic signal with topography; in nT/m; calculated from the residual magnetic field; southern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-5A

   Analytic signal with data contours; in nT/m; calculated from the residual magnetic field; northern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-5B

   Analytic signal with data contours; in nT/m; calculated from the residual magnetic field; southern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-6A

   Tilt derivative with topography and data contours; in degrees; calculated from residual magnetic field; northern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-6B

   Tilt derivative with topography and data contours; in degrees; calculated from residual magnetic field; southern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-7A

   Color shadow residual magnetic field with magnetic tilt derivative contours; color in nT; contours in degrees; northern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-7B

   Color shadow residual magnetic field with magnetic tilt derivative contours; color in nT; contours in degrees; southern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-8A

   56,000 Hz apparent coplanar resistivity with topography; in ohm m; northern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-8B

   56,000 Hz apparent coplanar resistivity with topography; in ohm m; southern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-9A

   56,000 Hz apparent coplanar resistivity with data contours; in ohm m; northern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-9B

   56,000 Hz apparent coplanar resistivity with data contours; in ohm m; southern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-10A

   7200 Hz apparent coplanar resistivity with topography; in ohm m; northern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-10B

   7200 Hz apparent coplanar resistivity with topography; in ohm m; southern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-11A

   7200 Hz apparent coplanar resistivity with data contours; in ohm m; northern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-11B

   7200 Hz apparent coplanar resistivity with data contours; in ohm m; southern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-12A

   900 Hz apparent coplanar resistivity with topography; in ohm m; northern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-12B

   900 Hz apparent coplanar resistivity with topography; in ohm m; southern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-13A

   900 Hz apparent coplanar resistivity with data contours; in ohm m; northern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-13B

   900 Hz apparent coplanar resistivity with data contours; in ohm m; southern sheet for southern Dishna River. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-14

   Residual magnetic field with topography; in nanoteslas (nT); Fox Hills. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-15

   Residual magnetic field with data contours; in nanoteslas (nT); Fox Hills. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-16

   First vertical derivative with topography; in nT/m; calculated from the residual magnetic field; Fox Hills. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-17

   with topography; in nT/m; calculated from the residual magnetic field; Fox Hills. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-18

   Analytic signal with data contours; in nT/m; calculated from the residual magnetic field; Fox Hills. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-19

   Tilt derivative with topography and data contours; in degrees; calculated from residual magnetic field; Fox Hills. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-20

   Color shadow residual magnetic field with magnetic tilt derivative contours; color in nT; contours in degrees; Fox Hills. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-21

   56,000 Hz apparent coplanar resistivity with topography; in ohm m; Fox Hills. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-22

   56,000 Hz apparent coplanar resistivity with data contours; in ohm m; Fox Hills. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-23

   7200 Hz apparent coplanar resistivity with topography; in ohm m; Fox Hills. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-24

   7200 Hz apparent coplanar resistivity with data contours; in ohm m; Fox Hills. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-25

   900 Hz apparent coplanar resistivity with topography; in ohm m; Fox Hills. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-26

   900 Hz apparent coplanar resistivity with data contours; in ohm m; Fox Hills. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-27

   Residual magnetic field with topography; in nanoteslas (nT); Beaver Creek. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-28

   Residual magnetic field with data contours; in nanoteslas (nT); Beaver Creek. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-29

   First vertical derivative with topography; in nT/m; calculated from the residual magnetic field; Beaver Creek. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-30

   Analytic signal with topography; in nT/m; calculated from the residual magnetic field; Beaver Creek. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-31

   Analytic signal with data contours; in nT/m; calculated from the residual magnetic field; Beaver Creek. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-32

   Tilt derivative with topography and data contours; in degrees; calculated from residual magnetic field; Beaver Creek. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-33

   Color shadow residual magnetic field with magnetic tilt derivative contours; color in nT; contours in degrees; Beaver Creek. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-34

   56,000 Hz apparent coplanar resistivity with topography; in ohm m; Beaver Creek. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-35

   56,000 Hz apparent coplanar resistivity with data contours; in ohm m; Beaver Creek. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-36

   7200 Hz apparent coplanar resistivity with topography; in ohm m; Beaver Creek. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-37

   7200 Hz apparent coplanar resistivity with data contours; in ohm m; Beaver Creek. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-38

   900 Hz apparent coplanar resistivity with topography; in ohm m; Beaver Creek. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   GPR2013-1-39

   900 Hz apparent coplanar resistivity with data contours; in ohm m; Beaver Creek. (Source: Fugro Airborne Surveys)

   map in PDF and HPGL/2 formats

   Entity_and_Attribute_Overview:

   All three linedata databases (SDishnaRiver, FoxHills, and BeaverCrk) have identical channels, which are described in 'gpr2013_001_linedata.txt', Fugro's linedata channel summary. The three linedata databases each have a 'Detailed_Description' below in this 'Entity_and_Attribute_Information' section. A more detailed definition is given for some entities in the detailed section than in the file 'gpr2013_001_linedata.txt'. Minimum and maximum values, plus values that have unrepresentable domains are given in the 'Entity_and_Attribute_Information' section. The linedata text file is easier to read. Each linedata file contains raw and processed linedata, and related calculated fields. Missing data are represented with the dummy variable '*'. Each of the flight lines (e.g., Line 40010, referred to as 'LINE' attribute) is associated with a 'DATE' (e.g., 2012/09/25), a 'FLIGHT (number)' (e.g., 3023), and a particular multi-record set of data. Each record represents data acquisition from one spatial location in the flight line.

   Entity_and_Attribute_Detail_Citation:

   L.E. Burns, Division of Geological & Geophysical Surveys and Fugro Airborne Surveys

   Entity_and_Attribute_Overview:

   Most geophysical images that were included in a map in this publication are placed on two maps, one with topography and one with data contours and no topography. Maps are provided in PDF and HPGL/2 format, and are downloadable in zip files by data format. The HPGL/2 files have brighter and more gradational colors, and sharper topography than the Adobe Acrobat files. See 'Technical_Prerequisites' section for more information on printing HPGL/2 maps.

   Thirteen maps are included for each area. All maps in this publication are at a scale of 1:63,360 (inch-to-a-mile). One map sheet each is needed to cover the Fox Hills and Beaver Creek areas. Two map sheets, labeled 'A' (north) and 'B' (south), are needed to cover the Dishna survey area at a scale of 1:63,360 (inch-to-a-mile).

   Entity_and_Attribute_Detail_Citation:

   L.E. Burns, Division of Geological & Geophysical Surveys, and Fugro Airborne Surveys

Who produced the data set?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • Burns, L.E.
   • Fugro Airborne Surveys Corp.
   • Fugro GeoServices, Inc.

2. Who also contributed to the data set?

   Funding was provided by the Alaska State Legislature the DGGS Airborne Geophysical/Geological Mineral Inventory (AGGMI) program.

3. To whom should users address questions about the data?

Why was the data set created?

The survey was part of the Alaska Airborne Geophysical/Geological Mineral Inventory Program funded by the Alaska State Legislature and managed by State of Alaska, Department of Natural Resources (DNR), Division of Geological & Geophysical Surveys (DGGS). The program seeks to catalyze private-sector mineral development investment. The program delineates mineral zones on Alaska state lands that: 1) have major economic value; 2) can be developed in the short term to provide high quality jobs for Alaska; and 3) will provide economic diversification to help offset the loss of Prudhoe Bay oil revenue.

How was the data set created?

1. From what previous works were the data drawn?

   Akima, 1970 (source 1 of 3)

   Akima, H., 1970, A new method of interpolation and smooth curve fitting based on local procedures: Journal of the Association of Computing Machinery v. 7, no. 4.

   Online Links:

   • None

   Type_of_Source_Media: paper

   Source_Contribution:

   Fugro Airborne Surveys used a modification of this method while making grids.

   Fraser, 1978 (source 2 of 3)

   Fraser, D.C., 1978, Resistivity mapping with an airborne multicoil electromagnetic system: Geophysics v. 43.

   Online Links:

   • None

   Type_of_Source_Media: paper

   Source_Contribution:

   Fugro Airborne Surveys used this method for calculating apparent depth and apparent resistivity.

   ADNR-LRIS, 1995 (source 3 of 3)

   Alaska Department of Natural Resources - Land Records Information Section, 1995, Alaska PLSS Section Grid: State of Alaska, Department of Natural Resources, Division, Land Records Information Section (LRIS), <http://mapper.landrecords.info/> (Anchorage, Alaska).

   Online Links:

   • <http://dnr.alaska.gov/SpatialUtility/SUC?cmd=vmd&layerid=45> (metadata)

   Other_Citation_Details: ESRI shape file format

   Type_of_Source_Media: online

   Source_Contribution:

   The downloaded section grid file, built from original protraction diagram data, was used as a starting point for the section grid digital file included in GPR 2013-1. Minor formatting modifications were made to the file. The section grid is used on the maps without topography and is provided in digital format in this publication. The ending date for content, given above, reflects the current metadata file for the Alaska PLSS Section Grid.

2. How were the data generated, processed, and modified?

   Date: 2012 (process 1 of 7)

   The airborne geophysical data were acquired between September 15th to November 2nd, 2012, with about three more days spent in each of the beginning and end of the survey. An Aerospatiale AS350B2 helicopter, was used for this survey, and was on October 23rd, 2012 it was joined by an Aerospatiale AS350B3 helicopter. Two DIGHEM (V) Electromagnetic (EM) systems and two airborne Scintrex CS3 cesium magnetometer sensors were used. The EM and magnetic sensors were flown at a height of 100 feet, with the magnetic sensor installed in the EM bird. In addition, the survey recorded data from radar and laser altimeters, GPS navigation system, 50/60 Hz monitors, and video camera.

   Flights were performed with the Aerospatiale AS-350-B2 helicopter for the Dishna area and most of the Beaver Creek area. The Aerospatiale AS-350-B3 helicopter was used for the Fox Hills area and one of the flights in the Beaver Creek survey area. Further information is in the linedata 'Entity_Attribute' sections. The helicopters were flown at a mean terrain clearance of 200 feet (61 m) on a heading of N20W (a heading of 160 degrees) for the flight lines for all the areas. Line spacing was one-quarter mile (402.3 m). Tie lines were flown on a heading of 70 degrees, perpendicular to the flight lines, and were spaced at intervals of approximately 3 miles (4,828 m).

   Novatel OEM4-G2L Global Positioning Systems were used for navigation and flight path recovery. The helicopter positions were derived every 0.5 seconds (2 Hz); the ground GPS base station data were collected at 1.0 second (1 Hz) intervals. The use of the differentially-corrected base station data results in a positional accuracy of better than five meters. The positional xy data are interpolated from 2 Hz to 10 Hz. Flight path positions were projected onto the Clarke 1866 (UTM zone 4N) spheroid, 1927 North American datum using a central meridian (CM) of 159 degrees, a north constant of 0, and an east constant of 500,000.

   Date: 2012 (process 2 of 7)

   The total magnetic field data were acquired with a sampling interval of 0.1 seconds. Data are contained in channels in the linedata files 'SDishnaRiver', 'FoxHills', and 'BeaverCrk'. All channels mentioned in this document are included in all three databases. Any mention of a channel applies to that channel in all the linedatat files. The spike-rejected raw magnetic data (channel 'mag_raw') were (1) corrected for measured system lag (resulting in the channel 'mag_lag'), (2) corrected for diurnal variations by subtraction of the digitally recorded base station magnetic data (resulting in the channel 'mag_diu'), (3) adjusted for regional variations (by subtracting IGRF model 2010, updated for date of flight and elevation variations), (4) leveled to the tie line data resulting in the final residual magnetic intensity (resulting in channel 'mag_rmi'),(5) manually leveled with final small microleveling, and (6) increased by a constant IGRF average value to restore the mag_rmi values to a total magnetic field channel (resulting in channel 'magIGRF'). Channels 'mag_rmi and 'magIGRF' were then interpolated onto a regular 80-m grid using a modified Akima (1970) technique.

   Data sources used in this process:

   • Akima, 1970

   Date: 2013 (process 3 of 7)

   Three different algorithms were applied to the total magnetic field 80 m grid, resulting in three magnetic derivative grids. The analytic signal grid (XXX_ASig, where 'XXX' is replaced by 'Dish', 'Fox', and 'Bvr' in the data files) is the total amplitude of all directions of magnetic gradient calculated from the sum of the squares of the three orthogonal gradients. Mapped highs in the calculated analytic signal of the magnetic parameter locate the anomalous source body edges and corners (e.g., contacts, fault/shear zones, basement fault block boundaries or lithologic contacts, etc.). Analytic signal maxima are located directly over faults and contacts, regardless of structural dip, and independently of the direction of the induced and/or remanent body magnetizations.

   The calculated magnetic tilt grid (XXX_TiltDer) is the angle between the horizontal gradient and the total vertical gradient, and is useful for identifying the depth and type of magnetic source. The tilt angle is positive over the source, crosses through zero at, or near, the edge of a vertical sided source, and is negative outside the source zone. It has the added advantage of responding equally well to shallow and deep sources and is able to resolve deeper sources that may be masked by larger responses caused by shallower sources.

   The first vertical derivative grid was calculated using a fast Fourier transform (FFT) based frequency-domain filtering algorithm. The vertical gradient algorithm enhances the response of magnetic bodies in the upper 500 m and attenuates the response of deeper bodies. The resulting (calculated) vertical gradient grid (XXX_1VD) provides better definition and resolution of near-surface magnetic units and helps to identify weak magnetic features that may not be evident in the total field data.

   All magnetic and derivative derivative magnetic grids were then resampled from the 80-m cell size down to a 25-m cell size using a modified Akima (1970) technique to produce the maps and final grids contained in this publication. When resampling the grids to a 25-m cell size, the original grids are scanned to determine the minimum and maximum values which the new grids are then limited to, avoiding extreme extrapolation errors between lines.

   Data sources used in this process:

   • Akima, 1970

   Date: 2013 (process 4 of 7)

   Two DIGHEM (V) EM systems were used on this project. Each measured inphase and quadrature components at five frequencies. The DIGHEM(V) BKS51 system, associated with the AS350B2 helicopter, used two vertical coaxial-coil pairs which operated at 1115 (1000) and 5482 (5500) Hz while three horizontal coplanar-coil pairs operated at 921 (900), 7279 (7200), and 56,320 (56,000) Hz. The DIGHEM(V) BKS54 system, associated with the AS350B3 helicopter, used two vertical coaxial-coil pairs which operated at 1115 (1000) and 5741 (5500) Hz while three horizontal coplanar-coil pairs operated at 884 (900), 7077 (7200), and 56,150 (56,000) Hz.

   EM data were sampled at 0.1 second intervals. The EM system responds to bedrock conductors, conductive overburden, and cultural sources. The EM inphase and quadrature data were drift corrected using base level data collected at high altitude (areas of no signal). Along-line filters are applied to the data to remove spheric spikes. The data were inspected for variations in phase, and a phase correction was applied to the data if necessary.

   The apparent resistivity and apparent depth were then calculated from the inphase and quadrature data for all coplanar frequencies. The calculation used the pseudo-layer (or buried) half-space model defined by Fraser (1978). This model consists of a resistive layer overlying a conductive half-space (or pseudo-layer). The apparent depth is defined as the sensor-source distance minus the measured altitude of the sensor above the ground. The apparent depth channels estimate the depth of a conductive half-space. The calculated apparent depth is the depth to the top of this conductive layer. The apparent depth (or thickness) parameter will be positive when the upper layer is more resistive than the underlying material, in which case the apparent depth may be quite close to the true depth, assuming it is a buried half-space and the altimeter is correct. The apparent depth will be negative when the upper layer is more conductive than the underlying material, and will be zero when a homogeneous half-space exists. The apparent depth parameter must be interpreted cautiously because it will contain any errors that might exist in the measured altitude of the EM bird (e.g., as caused by a dense tree cover). Manual leveling of the inphase and quadrature of each coil pair, based on the resistivity data and comparisons to the data from the other frequencies, was performed. Automated micro-leveling is carried out in areas of low signal.

   The EM data were interpolated onto a regular 80-m grid using a modified Akima (1970) technique. The resulting grids were subjected to a 3x3 Hanning filter and resampled to a 25-m cell size before contouring and map production. When resampling the grids to a 25-m cell size, the original grids are scanned to determine the minimum and maximum values which the new grids are then limited to, avoiding extreme extrapolation errors between lines.

   Data sources used in this process:

   • Akima, 1970

   Date: 2013 (process 5 of 7)

   The digital elevation/terrain model was produced from the differentially corrected GPS-Z data (channel 'GPSZ' in linedata files) and the laser altimeter data measured in the bird (channel 'ALTLAS_BIRD' in linedata). Both the GPSZ and ALTLAS_BIRD data were checked for spikes, which were removed manually. The ALTLAS_BIRD data were despiked and then filtered using a 13 median filter, followed by a 13 Hanning filter. The corrected altimeter was then subtracted from the GPSZ data to produce profiles of the height above mean sea level along the survey lines. The data were manually leveled to remove any errors between lines. After all leveling, the data were DC shifted to match the local maps, in this case, NAD27. The 80-m DTM grid was then resampled to a 25-m cell size to produce the DTM grid contained in this publication. When resampling the grids to a 25-m cell size, the original grids are scanned to determine the minimum and maximum values which the new grids are then limited to, avoiding extreme extrapolation errors between lines.

   Date: 2012 (process 6 of 7)

   DGGS downloaded the Alaska PLSS Section Grid shapefile in December 2012 and cut the file to roughly fit the map sheets for this publication using MapInfo Professional. Fugro Airborne Surveys modified the formatting of the file using AutoCad, changing township and range line widths and colors, and added township and range labels. The modified file was then used as overlays on maps without topography.

   Data sources used in this process:

   • ADNR-LRIS, 1995

   Date: 2013 (process 7 of 7)

   The HPGL/2 files were created with HP Designjet 5000 printer driver v5.32 and plot on some plotters, but not all plotters correctly. The Adobe Acrobat format files were created with Adobe Acrobat Distiller v9.0 from Postscript files.

3. What similar or related data should the user be aware of?

   Burns, L.E., Fugro Airborne Surveys Corp., and Fugro GeoServices, Inc., 2011, Iditarod survey area: Magnetic and electromagnetic line, grid, and vector data and maps, Innoko, Iditarod, and McGrath mining districts, Iditarod and Ophir quadrangles, western Alaska: Geophysical Report GPR 2011-2, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS), Fairbanks, AK, USA.

   Online Links:

   • <http://dx.doi.org/10.14509/22842>
   • <http://dggs.alaska.gov/pubs/gpdata/155>

   Other_Citation_Details: 1 DVD

   Burns, L.E., Stevens Exploration Management Corp., and Fugro Airborne Surveys Corp., 2000, DVD containing profile data, gridded data, vector data, and location information of 2000 geophysical survey data for parts of the Aniak and Iditarod mining districts, southwestern Alaska: Geophysical Report GPR 2000-38, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS), Fairbanks, AK, USA.

   Online Links:

   • <http://dx.doi.org/10.14509/2721>
   • <http://dggs.alaska.gov/pubs/gpdata/60>

   Other_Citation_Details: 1 DVD

   Stevens, Mark, and Fugro Airborne Surveys Corp., 2000, Project report of the geophysical survey of parts of the Aniak and Iditarod mining districts, southwestern Alaska:: Geophysical Report GPR 2000-40, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS), Fairbanks, AK, USA.

   Online Links:

   • <http://dx.doi.org/10.14509/2723>
   • <http://dggs.alaska.gov/pubs/gpdata/60>

   Other_Citation_Details: 1 DVD

   Burns, L.E., Fugro Airborne Surveys Corp., and Fugro GeoServices, Inc., 2011, Iditarod survey area: Magnetic and electromagnetic line, grid, and vector data and maps, Innoko, Iditarod, and McGrath mining districts, Iditarod and Ophir quadrangles, western Alaska: Geophysical Report GPR 2011-2, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS), Fairbanks, AK, USA.

   Online Links:

   • <http://dx.doi.org/10.14509/22842>
   • <http://dggs.alaska.gov/pubs/gpdata/155>

   Other_Citation_Details: 1 DVD

How reliable are the data; what problems remain in the data set?

1. How well have the observations been checked?

   Survey contracts specified the conditions and specifications under which these data were collected. Altimeter, heading, lag, and frequent EM calibrations were done. More information will be available in the project report to be published in the future.

2. How accurate are the geographic locations?

   The helicopter position was derived every 0.5 seconds using post-flight differential positioning to an accuracy of better than 1 m.

3. How accurate are the heights or depths?

   The laser altimeter ('ALTLAS_BIRD'), located in the bird (EM equipment and magnetometer housing), had a stated resolution of 0.10 meter. The ALTLAS_BIRD value may be unreliable over bodies of water where the laser returns are scattered.

4. Where are the gaps in the data? What is missing?

   The linedata files have very few missing values. More information is in 'gpr2013_001_linedata.txt'.

5. How consistent are the relationships among the observations, including topology?

   Data for this survey were collected by a single subcontractor (Fugro Airborne Surveys) who was responsible for collecting and processing the data.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints:

This report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).

Use_Constraints:

Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological &amp; Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

1. Who distributes the data set? (Distributor 1 of 1)
   Alaska Division of Geological & Geophysical Surveys
   3354 College Road
   Fairbanks, AK 99709-3707
   USA
   

   (907)451-5020 (voice)
   (907)451-5050 (FAX)
   dggspubs@alaska.gov
   

   Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays

   Contact_Instructions:

   Please view our website (<http://www.dggs.alaska.gov>) for the latest information on available data. Please contact us using the e-mail address provided above when possible.

2. What's the catalog number I need to order this data set?

   GPR 2013-1

3. What legal disclaimers am I supposed to read?

   The State of Alaska makes no expressed or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.

4. How can I download or order the data?
   • Availability in non-digital form:

     Current geophysics publications are available on paper or Mylar. Please ask for the maps to be printed from HPGL/2 files to ensure the best quality image. To purchase printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: cash, check, money order, VISA, or MasterCard.

   • Cost to order the data: Contact DGGS for current pricing

   • Availability in digital form:

     Data format:	Geosoft binary float (GRD) (version Unknown)
     Media you can order:	DVD (format Unspecified)

     Data format:	ER Mapper (ERS) (version Unknown)
     Media you can order:	DVD (format Unspecified)

     Data format:	Geosoft binary database (GDB) (version Unknown)
     Media you can order:	DVD (format Unspecified)

     Data format:	Geosoft ASCII (XYZ) (version Unknown)
     Media you can order:	DVD (format Unspecified)

     Data format:	ESRI Shape (SHP) (version Unknown)
     Media you can order:	DVD (format Unspecified)

     Data format:	PDF (version 1.5)
     Media you can order:	DVD (format Unspecified)

     Data format:	HPGL/2 (version unknown)
     Network links:	<http://dx.doi.org/10.14509/26701>
     Media you can order:	DVD (format Unspecified)

   • Cost to order the data:

     Digital files on DVD are available for $10 plus shipping and are free when downloaded online.

   • Special instructions:

     Order by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: cash, check, money order, VISA, or MasterCard. The geophysics page of the DGGS web site (<http://www.dggs.alaska.gov/pubs/geophysics>) has geophysical order forms for this project and others.

   • How long will it take to get the data?

     Digital downloads: less than 30 minutes for most files. Free FTP access is available upon request for files not available on the web. Offline CD/DVD-ROMs: 1-2 weeks unless special arrangements are made and an express fee is paid.

5. Is there some other way to get the data?

   DGGS publications are available as free online downloads or you may purchase paper hard-copies or digital files on CD/DVD or other digital storage media over the counter, by mail, phone, fax, or email from the DGGS Fairbanks office. Turnaround time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for exact shipping amount.

6. What hardware or software do I need in order to use the data set?

   Software with ability to use, import, or convert Geosoft float GRD, Geosoft binary GDB or ASCII XYZ files, Autocad DXF files, ESRI Shape files, Adobe Acrobat PDF, Google Earth files, and text files. Free downloadable interfaces to view or convert the gridded and dxf files are available at the Geosoft Web site (<http://www.geosoft.com>; Oasis Montaj viewer). The KMZ files can be dragged and dropped into the 'My Places' folder of the free downloadable 'Google Earth' software. Freeware software 'printfile' (<http://www.lerup.com/printfile/>) prints HPGL/2 files easily on compatible printers. The HPGL/2 files have brighter colors and sharper topography than the PDF maps and should be used for printing when possible. The PDF format maps are the only maps digitally viewable in this publication.

Who wrote the metadata?

Dates:

Last modified: 15-Nov-2013

Metadata author:

Alaska Division of Geological & Geophysical Surveys
Metadata Manager
3354 College Road
Fairbanks, AK 99709-3707
USA

(907)451-5020 (voice)

Metadata standard:

FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

Metadata extensions used:

• <http://www.dggs.alaska.gov/metadata/dggs.ext>