b'Minerals geophysics Minerals geophysicshighlighted calculation errors (e.g. usingGain Control to suppress anomaly the 2D apparent resistivity formula formagnitude differences. Local anomalies 3D electrode dispositions), errors in unitscan be enhanced by subtraction of an (gravity units processed as milligals), andappropriate background created by say, the inclusion of obviously invalid data. upward continuation. Alternatively, local If the data are only available in hard- anomalies may be better delineated via a copy form, extra effort will be involved.high pass filter such as the Butterworth. Where the hardcopy comprises dataThese are just some of the wide range of sheets (e.g. gravity, ground magnetics,processing options available.etc.) then digitisation can be achievedDifferent products can also be combined using optical character recognition (OCR)in the one presentation, using colour for technology (with some careful checkingone parameter and shading for another; Terry Harveyof the results if the original documentsternary presentations arent just for Associate Editor for are of poor quality). Where IP-resistivityradiometric channels either. There are Minerals geophysicssurvey results are only available asnot necessarily hard and fast rules for terry.v.harvey@glencore.com.au pseudosections, digitisation is morethissometimes its just a matter of efficient if you have a spreadsheet settrying various combinations (hopefully up to assign electrode dispositions onthe choices are intelligently informed) the fly; even better if the spreadsheetuntil you generate products that do Going that extra mile also formats the data for input intothe job. One thing thoughclearly your inversion routine. With hard copydocument and label what youve done. It data in profile form (e.g. magnetics,will help inform sensible interpretations With the modern processing andgravity, gradient array IP-resistivity,and will serve to remind you what presentation tools now at our disposal,etc.), manual digitisation can be moreworked this time. One of my hobby any geophysical assessment, whethertedious, particularly if the vertical scalehorses is proper labelling of products it involves evaluating newly acquiredis logarithmic. But it is doable. However,and, for images, inclusion of the relevant third party data or re-visiting existingdigitising multichannel EM data plottedcolour bar. It can be quite frustrating data, will offer opportunities to advanceat logarithmic scales from hard copyinterpreting an image that is unlabelled, knowledge. The key enablers for thisstacked sections may be a step too far.or even worse, incorrectly labelled. I nag advancement are the generation ofIf anyone out there has an automatedmy co-workers on this one, particularly appropriate geophysical products andprocess for this, Id be much obliged forwhere we have image captions like the presentations of those products forany information on how its done. structure over magnetics. What sort of optimal use by geophysicists and othermagnetics? There are a lot of different team members. Once you have the data in digital form,products out there. You may be able to Where third party geophysics areprocessing and presentation are at yourtell from the pattern style, then again you involved, such as information supplied asfingertips. Where in-house geophysicsmay not. Even if the image is properly part of a package for property evaluation,are involved, the data should alreadylabelled, without a colour bar you have or the results of historic surveysbe available and may well have beenno information on the amplitude range recovered from literature searches, theprocessed and presented. The aim hereand, if its not specified in the label, the information format will largely determineis to value-add. A typical request for a re- colour stretch.the extent of possible further processingassessment may come from a geologist and presentation work. Images alonewanting to view the geophysics availableThe ability to properly view geophysical are of limited use; you will be effectivelyfor a particular work area. There willinformation against available data restricted to looking at what everyoneprobably be regional or semi-regionalfrom other geoscience disciplines is else has already looked at. You may begeophysical surveys (e.g. magnetics,a very important factor in enhancing better informed than they were, but whyradiometrics, gravity, etc.) covering thethe interpretation process. The multi-not give yourself the best chance? Toarea, but whole-of-survey images willdisciplinary interpretation/presentation carry out further geophysical processing,be general in nature. One size does notpackages presently available, such as you need data. If digital data are notfit all. Leapfrog, GeoScience Analyst, GOCAD, already supplied, you may have toA good first step will be to window outMapInfo, etc., all have facilities enabling specifically request data files, or you maythe data for the work area and generatethe import of geophysical products when have to derive the data from hard copy.products and bespoke images tailoredpresented in the appropriate format.Located data are best, but gridded datato the geologists particular needs. This may well suffice. As well as offering moreis particularly pertinent if geologicalSo give yourself and your team the flexibility in further processing, havingmapping and structural assessment arebest possible chance and invest effort located data will allow you to reviewpart of the program. Pattern recognitionin presenting those new products the geophysics for quality control. Mywill be enhanced on vertical derivativethat youve just generated in the most past reviews of data have occasionallyimages, and by the use of Automaticappropriate formats.AUGUST 2020 PREVIEW 28'