**Aerogeophysical survey description**

**The survey includes three survey methods:**

- Magnetic total field measurements
- Dual-frequency electromagnetic measurements
- Radiometric gamma-ray measurements

**Survey equipment**

QDS map sheets 30-31, 44-45, 62, 78 (Twin Otter aircraft)

**Two Caesium magnetometers installed at the wing tips**

- Distance 21.36 meters
- Registration frequency 10 Hz

**Dual-frequency electromagnetic unit**

- Coil distance 21.36 meters
- Lower frequency 3 125 Hz, higher frequency 14 368 Hz
- Registration frequency 4 Hz

**Gamma-ray spectrometers**

- Two sets of NaI crystal units (four downward and one upward looking crystal)
- Total volume 42 liters
- 256 channels, energy range 0.01 – 3.00 MeV
- Registration frequency 1 Hz

QDS map sheets 4-5, 12-13, 153-155 (Cessna Caravan aircraft)

**One Caesium magnetometer installed at a back boom**

Registration frequency 10 Hz

**Dual-frequency electromagnetic unit**

- Coil distance 21.36 meters
- Lower frequency 3 125 Hz, higher frequency 14 368 Hz
- Registration frequency 4 Hz

**Gamma-ray spectrometers**

- Two sets of NaI crystal units (four downward and one upward looking crystal)
- Total volume 42 liters
- 256 channels, energy range 0.01 – 3.00 MeV
- Registration frequency 1 Hz

**Data format description**

**XYZ Files**

There is one Geosoft XYZ file corresponding to each survey method (magnetic, radiometric and electromagnetic measurements) and each QDS map sheet. In addition to the measured component files there are also separate files for calculated apparent resistivities, digital terrain models and total gamma-ray dose data.

As the map sheets 4-5, 12-13 and 153-155 were surveyed using one magnetometer whereas on the map sheets 30-31, 44-45, 62 and 78, two magnetometers were used, there are two different naming conventions and file structures for magnetic data files.

**The files are named as follows (# means the varying QDS map sheet number):**

AP#.XYZ apparent resistivity data (all map sheets)

DTM#.XYZ digital terrain model (all map sheets)

EM#.XYZ electromagnetic data (all map sheets)

MB#.XYZ back boom magnetometer data (map sheets 4-5, 12-13, 153-155)

ML#.XYZ left wingtip magnetometer data (map sheets 30-31, 44-45, 62, 78)

MR#.XYZ right wingtip magnetometer data (map sheets 30-31, 44-45, 62, 78)

RA#.XYZ radiometric data (all map sheets)

TO#.XYZ gamma-ray dose data (all map sheets)

**XYZ File Columns**

Each row in these ASCII files corresponds to one measurement point. One column of the row corresponds to one measurement parameter.

The data includes the following columns:

**Electromagnetic data files**

X, Y ARC1960 coordinate pair X, Y (easting, northing respectively) (meters)

DAY Day number from the beginning of the year

TIME Measurement time stamp (hhmmss)

DIR Flight direction (degrees, clockwise from north)

RALT Radar altitude (meters)

LFR In-phase component of the lower frequency (3 005 / 3 125 Hz) (ppm)

LFI Quadrature component of the lower frequency (3 005 / 3 125 Hz) (ppm)

HFR In-phase component of the higher frequency (14 368 Hz) (ppm)

HFI Quadrature component of the higher frequency (14 368 Hz) (ppm)

**Magnetic data files: map sheets 4-5, 12-13, 153-155**

X, Y ARC1960 coordinate pair X, Y (easting, northing respectively) (meters)

DAY Day number from the beginning of the year

TIME Measurement time stamp (hhmmss)

DIR Flight direction (degrees, clockwise from north)

RALT Radar altitude (meters)

MB65 Total magnetic field of the back boom magnetometer at IGRF65 level (nT)

**Magnetic data files: map sheets 30-31, 44-45, 62, 78**

X, Y ARC1960 coordinate pair X, Y (easting, northing respectively) (meters)

DAY Day number from the beginning of the year

TIME Measurement time stamp (hhmmss)

DIR Flight direction (degrees, clockwise from north)

RALT Radar altitude (meters)

ML65 Total magnetic field of the left wingtip magnetometer at IGRF65 level (nT)

MR65 Total magnetic field of the right wingtip magnetometer at IGRF65 level (nT)

**Radiometric data files**

X, Y ARC1960 coordinate pair X, Y (easting, northing respectively) (meters)

DAY Day number from the beginning of the year

TIME Measurement time stamp (hhmmss)

DIR Flight direction (degrees, clockwise from north)

RALT Radar altitude (meters)

BALT Barometric altitude (m)

TOUT Temperature outside the aircraft (°C)

D_KAL Potassium concentration (% K)

D_URA Uranium concentration (ppm equivalent uranium eU)

D_THO Thorium concentration (ppm equivalent thorium eTh)

**Apparent resistivity data files**

X, Y ARC1960 coordinate pair X, Y (easting, northing respectively) (meters)

DAY Day number from the beginning of the year

TIME Measurement time stamp (hhmmss)

DIR Flight direction (degrees, clockwise from north)

RALT Radar altitude (meters)

LFA Calculated lower frequency (3 005 / 3 125 Hz) apparent resistivity (m)

LFS Calculated apparent depth corresponding to LFA (m)

HFA Calculated higher frequency (14 368 Hz) apparent resistivity (m)

HFS Calculated apparent depth corresponding to HFA (m)

**Digital terrain model files**

X, Y ARC1960 coordinate pair X, Y (easting, northing respectively) (meters)

DAY Day number from the beginning of the year

TIME Measurement time stamp (hhmmss)

DIR Flight direction (degrees, clockwise from north)

RALT Radar altitude (meters)

DTM Digital terrain model above the WGS84 ellipsoid (m)

**Gamma-ray dose data**

X, Y ARC1960 coordinate pair X, Y (easting, northing respectively) (meters)

DAY Day number from the beginning of the year

TIME Measurement time stamp (hhmmss)

DIR Flight direction (degrees, clockwise from north)

RALT Radar altitude (meters)

BALT Barometric altitude (m)

08:38:50TOUT Temperature outside the aircraft (°C)

D_TOT Dose rate (nGy/h

**Grids**

The grids are interpolated with the minimum curvature algorithm of Geosoft Oasis Montaj for all the parameters except apparent resistivity in which Akima spline method is used. Grid cell size is 50 meters for all the grids.

There is a corresponding grid for all the geophysical parameters of each map sheet. In addition there are also grids for digital terrain models (base level WGS84 ellipsoid). The units of the grid values correspond to those in the XYZ files.

**Grids are named as follows (# means the varying QDS map sheet number)**:

DTM#.GRD Digital terrain model

HFA#.GRD Higher frequency (14 368 Hz) apparent resistivity

HFI#.GRD Higher frequency (14 368 Hz) EM quadrature component

HFR#.GRD Higher frequency (14 368 Hz) EM in-phase component

KAL#.GRD Potassium

LFA#.GRD Lower frequency (3 005 / 3 125 Hz) apparent resistivity

LFI#.GRD Lower frequency (3 005 / 3 125 Hz) EM quadrature component

LFR#.GRD Lower frequency (3 005 / 3 125 Hz) EM in-phase component

MAG#.GRD Magnetic total field

THO#.GRD Thorium

TOT#.GRD Total radiation dose rate

URA#.GRD Uranium