Airborne Geophysics
Is responsible for all aspects of airborne geophysical surveys to promote mineral exploration with the aim of
identifying potential new mine targets. The most important parameters measured are conductivity, magnetic
susceptibility, rock density, radioactive element concentration, and reflectance spectra.
In addition to the Regional Airborne magnetic data set, a national programme of high resolution magnetics and
radiometrics has been completed, and other airborne surveys undertaken in recent years include electromagnetics,
hyperspectral scanning and gravity.
High Resolution Airborne Index
Magnetics
Some 41 different surveys flown between 1962 and 1992 were homogenised and merged within the framework of technical co-operation
between the Geological Survey of Namibia and the Bundesanstalt für Geowissenschaften und Rohstoffe (BGR), Germany. Data are
available as whole area grids with 2000 m, 500 m and 200 m cell size and scissored according to the Namibian Map System in 1:250.000
map sheets (500 m cell size) and 1:50.000 map sheets (200 m cell size)
Regional airborne magnetic map
Radiometrics
Within the framework of technical co-operation between the Geological Survey of Namibia and the Bundesanstalt für Geowissenschaften
und Rohstoffe (BGR), Germany, data were back-calibrated covering an area of 11 1:250.000 map sheets. To merge different surveys of
varying quality, the data had to be back-calibrated using ground control points. Counts per second were transferred into ground
concentrations of the three radioactive elements Potassium, Uranium, Thorium and into Exposure Rate (Total Counts) using calibrated
hand held 256 channel spectrometers. These data are available in gridded format scissored according to the Namibian Map System as
1:250.000 map sheets with 250m
Regional radiometric map
Airborne Gravity
In 2004, a GT-1A airborne gravity test survey flown at 80m AGL was conducted by GPX Survey in the Rehoboth, Grootfontein
and Bushmen areas.
The acquired data was processed but yet to be interpreted. The respective datasets from these survey areas are available at
the GSN in a Geosoft format.
High Resolution Airborne Geophysics
The programme of High Resolution Airborne Geophysical surveys comprising of 200 m line spacing and a ground clearance of
80 m to 100 m started in 1994. Data acquired included magnetic and radiometric and to date over 4.4 million line-kilometers
of data are available with a complete national coverage at 97 %. Digital data are available in gridded format and as located
line data to allow customized tailored reprocessing and line data interpretation. These data are sold at rate of N$1 per
line km (or N$5 per square kilometres) for the complete data set or N$ 0.5 per line km (or N$2.75 per square kilometres)
for gridded data only. Other products are available such as Geotiffs and further information can be obtained by contacting
the Geological Survey.
Airborne Electromagnetic
In 2011, Fugro Airborne Surveys were contracted to survey 90 000 sq. km area of airborne EM data over the North Eastern (NE)
part of Namibia which successfully penetrated overlying Kalahari sediments and were able to further characterize and map the
underlying bedrock geology and also mapped sulphide deposit and palaeo-channels. Structures such as lithologic contacts, drainage
patterns and palaeo-channels, alterations zones, structural faults has been mapped with the EM survey in addition to the
available magnetic and gravity data.
In 2005, Fugro Airborne Surveys were contracted to survey 4,500 line Kms in two areas located near the Eiseb in the Otjozondjupa
Region using their fixed wing TEMPEST time domain EM system. Later, in 2008 Geotech Limited were contracted to survey 3310 line
Kms in the Maroelaboom Areas, located some 50 kms north east of Grootfontein, using their helicopter borne VTEM time domain system.
Subsequently to that, two more surveys were flown in the Erongo region mainly; Trekkopie and Lofdal surveys. However, the final
data on these surveys' are yet to be processed. All of these surveys successfully penetrated overlying Kalahari sediments and were
able to further characterize and map the underlying bedrock geology, the Damara Orogenic Belt. The surveys also indentified bedrock
conductors beneath the Kalahari sediments, thus increasing the mineral potential within the region as a whole.
Regional Airborne Geophysical Data
During a thirty year period nearly all of Namibia was gradually covered by regional airborne geophysical (magnetic and radiometric)
surveys with typical 1000-m line spacing and a ground clearance between 100 and 150 m.
Radiometric Calibration Facilities
Radiometric surveys have become increasingly important for mineral exploration and environmental studies, especially
since data quality has improved by modern spectral processing. The calibration of airborne and ground instruments,
making use of calibration pads and a Dynamic Calibration Range, is essential to achieve comparable results in units of
ground concentration. Calibration pads are available at the Eros Airport close to the Geological Survey in Windhoek.
The Dynamic Calibration Range is situated close to Henties Bay at the central Namibian coast. The area meets the criteria defined by
the International Atomic Energy Agency (IAEA) in 1991. The range consists of a flat 2 x 11 km wide area stretching approximately 1 km
inland along the coast, that was surveyed on a 100 x 100 m grid using calibrated hand held instruments. A nearby airstrip and the airport
of Swakopmund, 60 km to the south, complete the facilities. Digital data and hardcopy maps of the Dynamic Calibration Range can be made
available to all interested parties.
Hyperspectral
Hyperspectral survey were conducted as from 2004 and the covered areas are Otavi, Sikereti, Mowe Bay, Erongo region, Erindi,
Navachab, and Rehoboth as it can be seen on the index map. With this tool you can map out alterations minerals for exploration purpose.
