This dataset is part of the Geological Survey NSW Geophysics dataset series. Bouguer gravity that has been isostatically corrected in pseudocolour, superimposed on a greyscale intensity layer showing tilt-filtered total magnetic intensity reduced to the pole. Isostatic correction of the gravity data removes the contribution due to Airy isostasy, the effect in which the depth of the base of the crust is greater in regions of higher topography. Variations in isostatically-corrected gravity should directly reflect differences in the geology of the crust, rather than its thickness. The tilt-filter is a variety of phase filter which, like the more familiar first vertical derivative of TMI (TMI 1VD), traces geological structures. Unlike TMI 1VD however, the tilt-filter is relatively insensitive to the depth of the source geology below the ground, making tilt-filtered TMI a useful tool for tracing geological structure below variable depths of sedimentary cover. Isostatic gravity shares the same units as Bouguer gravity (µms -2). The output of the tilt-filter is an angle, varying between -π/2 and +π/2 radians (i.e. -90° to +90°). This is not related to the strength of the magnetic anomaly, but the spacing between contours of equal tilt angle is related to the depth of the source.

This dataset is part of the Geological Survey NSW Geophysics dataset series. Isostatic spherical-cap Bouguer gravity data. The image is a pseudocolour layer with a histogram-equalised colour stretch. Cooler colours indicate lower values and warmer colours represent increasingly higher Bouguer gravity values. The image shows the Earth’s gravity response to variations in the crustal rock density, after removal of broad gravity highs and lows caused by changes in crustal thickness. Gravity data are presented after removal of latitude and 'free-air' corrections, Bouguer corrections (assuming a crustal density of 2.67 T/m3) and subtraction of gravity due to a model of the isostatic response to changes in elevation. The hue-saturation-intensity image was prepared by applying a 3x3 sun filter using an algorithm developed by NSW Trade & Investment. Sun illumination has been applied at 65 degrees elevation and 90 degrees azimuth.

This dataset is part of the Geological Survey NSW Geophysics dataset series. Ternary radioelement potassium(K)-thorium(Th)-uranium(U) channel data. The image was generated by merging many individual airborne surveys and is a red-green-blue (RGB) composite using a histogram-equalised colour-stretch for each of the three channels. The red, green and blue channels represent K, Th and U respectively. Mixed compositions are indicated by the proportional blend of the corresponding additive primary colours (e.g. yellow indicates the presence of both K and Th, magenta the presence of K and U while aqua indicates the presence of Th and U). Black indicates low concentrations and white represents high concentrations for all three radioelements. The distribution of radioelements reflects the geochemistry and mineralogy of the near-surface, which may constitute either bedrock or regolith materials. The NSW statewide grid DVD set includes K values in percent(%), Th values in parts per million (ppm) and U values in parts per million (ppm).