b'Minerals geophysics Minerals geophysicsPreserving industryFollowing up on one of the points Des makes, I have noticed that the experience performance of inversion software can be a de facto indicator of In a chat Des FitzGerald and I had at thegeophysical data quality. Certainly, last AEGC Conference in Perth, one ofif something is seriously awry with the subjects we discussed was how canthe data, an inversion can go off-the accumulated practical experiencetrack, and the degrees of fit may of industry stalwarts be preserved andbe poor. But, more subtly, the path utilised. I think Des article Qualityan inversion takes can sometimes Control in Airborne Geophysics inbe an indicator that something this issue of Preview is one such way.is not quite right. Of course, such Des practical experience comes to thebehaviour is more readily identified Terry Harveyfore in his contribution, and havingif you are familiar with the normal Associate Editor ready access to the article is one way ofperformance of the inversion for Minerals geophysicsderiving benefits from his experience.process. Experience does firstname.lastname@example.org Quality control is not something I haveFinally, if you feel that you may have a addressed in previous issues, so theMinerals Geophysics contribution to subject matter is timely. make to Preview, please get in touch.Quality control in airborne geophysicsgeophysical surveys, both during theworking within specifications. The survey acquisition phase and also when theprocessing engineer typically has access contractor is delivering the final versions. to each flight of data within a few hours, Geophysical surveying practice continuesand standard post-processing steps are to evolve at quite a rapid rate, with newundertaken to also check to a first order and improved systems regularly comingthat all the data appears to be in order. on to the market, promising higherThis checking remains in the realm of a resolution and better accuracy andtime series. One or more geophysicists are repeatability etc. then tasked with preliminary processing to produce located flight lines that are Airborne magnetics or ground gravityde-spiked and trimmed to the required data collected in the 1990s is graduallysurvey line specifications. This data can being relegated to the status ofthen have progressive grids created so D. J. FitzGerald legacy, and new surveys are beingthat any variations from flight to flight or Intrepid Geophysics, Australia.commissioned. Starting from theday to day become apparent. A diligent email@example.com mid-2000s, airborne electromagneticsindependent quality assurance process is (AEM) and gradiometry can providethen added to the process with the aim much superior products to interpretof reproducing the preliminary results, Introduction geology, etc. Horsfall (1997) outlinesand making requests for re-flights if the equipment calibration and field datadata is out of specifications. A contractor Quality control of airborne geophysicsquality checking procedures that haveshould not be allowed to demobilise and surveys is a complex subject. Thenot altered much since then for magneticleave the survey until a formal process discipline has continuously developedand radiometric surveying. of verifying a viable and in-specification over more than 60 years. The primarydata set has been achieved.checks on quality are those of commonAll members of an airborne survey crew sense and the outcome of the surveyedand client (or their representative) have a representation of the measured fieldrole to play in delivering a safely acquiredInfluence of government creating a geologically sensible basisquality product. The skill of the pilotregulationsfor interpretation, at a scale andalways contributes, as the specifications resolution that is required. Of thefor the flight path and minimisationSome governments require all common geophysical explorationof influences such as turbulence areexploration geophysics datasets to techniques, gravity, magnetics, inductivecritical. The field technicians role involvesvest back with the government after electromagnetics (EM) and radiometricsmaking sure the acquisition systeman exclusive period. This then sets up have long histories of successfuland the instruments are running anda long-term archive and repurposing development of airborne systems andproducing useable data. At the start andactivity. Australia can be seen to be at the applications. Large institutions haveend of each flight and each day, repeatforefront of this style of activity, resulting learnt from experience to always havelines might be required to be acquiredin continental scale compilations at a process of independently checkingto check that the instruments remainsurvey resolutions of gravity, magnetics, 35 PREVIEW APRIL 2020'