GIS-BASED IMAGE-ENHANCEMENT OF CONDUCTIVITY AND MAGNETIC-SUSCEPTIBILITY DATA FROM URETURITURI PA AND FORT RESOLUTION, NEW-ZEALAND

Two geographic information system (GIS) techniques for displaying, ana lyzing, and interpreting geophysical data were recently applied at two archaeological sites in northern New Zealand; a pre-European Maori pa (fortification), and a late nineteenth-century European fortification . A GIS was used to stretch and filter the conductivity data from the pa to accentuate subtle contrasts and clearly delineate boundaries bet ween areas with contrasting conductivity readings. Magnetic susceptibi lity data and two different bands of conductivity data from the histor ic fort were used as input for a GIS-based unsupervised classification . The classification delineated five spatial entities, several of whic h corresponded to known archaeological features. The interpretability of the geophysical data in in relation to conventional visual analysis of conductivity contour maps was enhanced through the use of the GIS procedures outlined.