Spectra Plus Processing for Airborne Gamma-Ray Spectrometry

Since 1995, Fugro Airborne Surveys has been able to offer its Spectra PlusT 256 channel enhanced processing for recorded airborne gamma-ray spectrometry (AGS) data. Spectra Plus can be applied to newly acquired or existing airborne AGS data to further enhance the quality of data presentation and interpretation. 

Spectra Plus can be shown to significantly increase sensitivity, while improving the signal to noise ratio making it ideally suited to low count rate data sets.

Enhanced Processing Technique for AGS Data 

The Spectra Plus processing method uses the entire 256 channels of recorded AGS data for calculating gamma activity. Modelling is performed using Monte-Carlo photon-transport code which accounts for all photon-matter interactions between the source and the detector.

The result of the modelling is a set of unit response spectra functions for particular radioelements at various altitudes. The unit response function represents the spectrum shape which is collected in a spectrometer.

Spectra Plus then fits the response functions to the measured spectra (background removed) over the full 256 channels. This results in the mass and surface activities or radioelement concentration for each one second spectrum.

Spectra Plus Features 

• Spatial resolution of the data is maintained throughout the processing cycle.

• Provides unmatched reductions in statistical noise especially for Uranium signal processing and imaging.

• Enhances regions of low radiation for improved resolution aiding the interpretation of AGS result.

• Provides improved data quality for areas of heavy vegetation, ground moisture or soil cover.

• Improved detector sensitivity provides more coherent images for mapping alteration systems which otherwise may not be identified.

• Superior techniques for environmental monitoring and searching for natural or man-made radioactive sources.

• Directional sensing information provides improved positioning of measured data.

• Stable data images that can be further processed using downward continuation techniques.

Spectra Plus is a recognised technique within the IAEA Report 323. It has been positively assessed by the Australian Nuclear Science Technology Organisation (ANSTO/C480) and the Czech Institute for Metrology, Department for ionising radiation.

Spectra Plus has been used extensively by Australian government organisations and major exploration companies for the reprocessing of existing 256 channel data for large regional surveys, and reprocessing for major exploration companies.

Examples below show Spectra Plus processing compared to standard Windows processing. for airborne data collected at 200metre line spacing at a flying height of 80metres. These images are shown at approximately 1:250,000scale.

Standard Windows Processing	Spectra Plus Processing