b'Bouguer corrections FeaturePreamble to Universal horizontal slab and spherical cap Bouguer correctionsTO Richard from Desrichardpretty good effort. Needs a bit of upgrading to be a full technical paper of greater benefit to the community.I am happy with the figures, the explanation, the layout, and the development of the argument.It is almost ready for cut and paste into the training material.I think Domink had already done this work as well with our code, after the paper was published.Des FitzgeraldA couple of suggestions.des@intrepid-geophysics.com a. please discuss the infinite slab option vs Cap for the radiometry case. We simply state that a simple Bouguer correction makes no sense for the infinite slab.In the year before he died Richard Lane spent a lot of time onAs you point out, the spherical cap does make a small difference in the compilation of continental gravity data for Australia\x08 Thisthe case of gradiometry.was the first time that he applied himself to this subject, despiteb. Central to the paper is the notion of vertical component. You being involved on the sidelines during previous updates\x08 have avoided the obvious issue of, and some difficulties, of how do It would be fair to say that, with the retirement of many of theyou define vertical?geophysicists at GA with years of practical experience of dealingI raise this, as this is rarely discussed. Sander have all the with gravity surveys, Richard, with the help of Phillip Wynne,components, so how does the spherical cap correction effect the was last man standing\x08 His determination to apply rigour to thetwo horizontal components?task led him to reflect on aspects not often checked\x08c. I think I have only ever seen the rationale for 166.7 km explained Notable issues addressed by Richard included: once. There is also an old earth curvature correction we use, passed Blending old and new land gravity surveys to create the bestdown from Mario and prior practise. This is tied to the 166.7 km representation of the field while suppressing the noise andfigure.historic errors and inconsistencies in the data d. Typo in abstract with the sentence starting Armed with these Adjusting for the Earths curvature, and how this might resulttools. slab or sphericalin improvements to simple assumptions (this is the subject of the following draft paper)\x08 desChecking and improving on the final continental correctionFROM Richard to Desfor deep mountain range roots i\x08e\x08 the isostatic correction (he prepared notes on why the original USGS implementationHello Des.missed one of the factors)\x08Thanks for your comments and suggestions.Some of our correspondence in regard to these matters is reproduced below: == = == Correspondence: d) This typo has been corrected. ThanksFROM Richard to Des == = == Hello Des. a) GradiometryWith the benefit (?) of being at home, I have completed a draft ofThanks for drawing my attention to this subject. As you note, a paper on spherical cap Bouguer corrections (see attached). Thisthe gradients for an infinite horizontal slab are all zero, so the rounds off some work that Dominik started some years ago. I dontcorrections for this geometry are trivially zero. In contrast, the know why, but his paper left out the spherical cap solution forvertical gradient is non-zero for a spherical cap geometry. I can offshore airborne observations. I thought that I would tidy this up. certainly add this qualitative information to the paper.I wonder if you could cast your eye over the manuscript and letThe development of the mathematics for the vertical gradient me know if there are things that I could do to improve it? Orwould be a significant undertaking. My feeling is that this should alternatively if I should forget about it! be left for another day and another paper.On another subject, has there been any progress with the isostatic== = == = corrections?b) What is vertical?Hope that you are staying busy and healthy.For Sander with their AIRGrav system, vertical is defined withRichard respect to the ellipsoid. This means that there can be non-zero 41 PREVIEW APRIL 2021'