Geophysical & Geochemical Surveys
Geothermal Project
High resolution airborne geophysical data
GTK Project

New high resolution airborne geophysical data on selected areas in tanzania (flown by geological survey of finland in 2003)

GTK and GST have completed high-resolution airborne geophysical surveys in Mpanda, Kahama, Biharamulo and Mara areas in Tanzania, covering approximately 30,000 square kilometres. The surveys were carried out in 2003 with two aircrafts, flying at a low altitude of 45 meters. The new airborne geophysical data is available at the Geological Survey of Tanzania (price list)

The new airborne geophysical survey data are complemented by geophysical interpretation, geological and geochemical surveys covering Kahama (QDS 62 and 78), Biharamulo (QDS 30 and 44) and Mpanda (QDS 153)

high
                                                          resolution
                                                          magnetic map
high resolution magnetic map


high resolution DEM


high resolution total radiometric map



















Map of surveyed  areas (to be redrawn
Technical specifications

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

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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

Contacts:      info@gst.go.tz
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