online spreadsheets. These spreadsheets contain all the QC communication, can be edited by all approved personnel and retain revision history. The GCAS employed laser altimeters as part of the survey equipment for the first time in a South Australian regional dataset. Laser altimeter data needed to be assessed carefully, mainly because of the intensely directional nature of the laser when compared to conventional radar altimeters that have a cone shaped detection zone. Contractors were required to fly a set of pre-survey test lines near Whyalla in South Australia (The Whyalla Test Lines), which allowed direct comparison of each system employed by the contractors on the GCAS. The Whyalla Test Lines extended over Spencer Gulf, with the over water sections of the test lines used to check aircraft and cosmic gamma ray backgrounds. The final digital elevation models, magnetic field and equivalent ground concentrations calculated by the contractors under the Whyalla Test Lines were compared, allowing evaluation of system calibration and corrections. Enhancements and analytic products GSSA encouraged and facilitated uptake of the GCAS data in geological mapping and exploration programmes by releasing a suite of data enhancements and depth analysis products for each survey block. These enhancements were provided in consistent industry formats for each block, making the data much more easily accessible. A major focus of the enhancements was the integration of the new magnetic data with the state-wide gravity coverage. Integration of gravity and magnetics is crucial for geological interpretation, particularly over the Gawler Craton where the combined data sets are essential for IOGC studies. However, selection and processing of gravity data can be time- consuming. We learnt two key lessons in this process. The first is that we should recover additional information from the gravity field in any area where there are closer spaced stations. Even in areas with a gravity station spacing of 400 m, it is clear that even closer spaced stations could reveal even more information. Secondly, we have found that combined gravity and magnetic vectors are more easily evaluated than side-by-side gravity and magnetic images, or a single complex image. We derived a suite of edge enhancement contours (“worms”) from the gravity data, and selected the level carrying the most coherent information. We then derived a suite of magnetic worms, from which we selected the level with strongest correlation to the gravity worm. These two worms, colour coded, are then combined and can be overlain on any images. In some cases the two worms are coincident, in other cases individual worms may trace separate segments of a feature not continuous in either data set, or one worm may highlight cross-cutting structures evident as terminations of the other. An example area is shown in Figure 2. We are confident that this data product will prove useful for structural interpretation. Those who have proprietary methods of data analysis can, of course, derive their own enhancements from the primary data. We supply our enhancements in a variety of formats suitable for import to ESRI ARCGIS, Geosoft, MapInfo/Discover, QGIS or Google Earth, and also supply PA sessions that can be viewed in PA or PA Viewer. There is also a brief report on derivation of the enhancement products and source depth solutions for each block. Magnetic source solutions Magnetic field data is collected at great cost and considerable care, but often source depth information is derived from that data using an automated“shot- gun”approach. Information about the depth to magnetisation is only available at select locations, and recovery of that information requires exact focus to derive the most reliable estimates. Unfortunately, this inverse problem is Figure 3.  Example “sweet-spot” magnetic depth section of a selected grid traverse. Left: purple = regional field, black = measured TMI, red = model computed, right: section over TMI image). Figure 2.  Magnetic (red) and gravity (blue) worms for area 4B (Fowler). Most other areas have higher density of gravity coverage and show greater detail. News Geophysics in the Surveys 25 PREVIEW JUNE 2019