INTERPRETATION OF AIRBORNE GAMMA-RAY SPECTROMETRY DATA FROM SUDBURY, ONTARIO

Digital image processing and enhancement techniques have been applied to airborne gamma ray spectrometry data from Sudbury, Ontario. These r esults have been correlated and compared with the available geological maps to evaluate their usefulness for identifying lithological units. Digital processing allows the correlation of various data sets, and d ifferent com ns of images can be tested and viewed as a composite imag e. Composite images with pseudo-colours provide an opportunity to anal yze and correlate information that is not otherwise apparent in indivi dual images. Principal component analysis has been applied to the gamm a ray spectrometry data to evaluate their efficacy and relative inform ation contents of the measured and computed data. The results of this study indicate that the combined radioelements image (obtained by comb ining the radioelement image and the ratio images) is effective for de fining areas of relative concentration of a specific element in near s urface materials. Furthermore, the composite radioelements image (prod uced by combining three separate radioelement images) and composite pr incipal components image reflect large-scale lithological variations