Alan, I was intrigued to see Rich’s name again after I have just included it in a review I am doing on data processing in Australia. As I ran Geometrics in Australia I know we certainly used the reduction in spacing that appeared to be the case, as a selling point for horizontal gradient flying but I don’t know about the proof that it was exactly halved. It did seem to be true in reality. Because I just had correspondence with Ian Lilly who worked for Geometrics and liased with Rich and was much closer to the processing than I was, below is Ian’s reply to my asking if he knew the whereabouts of the proof. (The 'pencil and paper' seems right for Rich)
I remember Rich doing the proof in pencil on a yellow pad during one of my visits to Sunnyvale. I have a very vague and possibly faulty recollection that geoMetrics published a simplified version in something like a tech note when they were trying to garner interest in gradiometers. I am not aware of the “tech note” (anymore, at least!). Maybe someone in Geometrics or Dick Wold, who was involved at the time, knows more. I hope you can track it down. Regards Roger Henderson > On 19 Feb 2019, at 7:45 pm, Alan Reid via SEGMIN <[email protected]> > wrote: > > Dear GrvMag and SEGMin listers > > I’m addressing both lists because the matter concerns both… > > Years ago, the late great Richard Hansen told me he’d proved that, for a > conventional airborne magnetic total field survey, cross-line gradient > measurements gave you the equivalent of halving the line spacing. The proof > was for noise-free data, but hey, it's an indication of a usefulness that’s > widely recognised and exploited. > > I subsequently asked Richard for his proof and he’d lost it, but he re-proved > it another way. Regrettably, I’ve now also lost that proof. And Richard is no > longer available to ask…… Hence the enquiry and the challenge. > > 1. Does anyone know of a published proof? If so, please may we have the > reference (and even maybe a link to a pdf? > > 2. If not, does anyone have a proof they’d be prepared to offer for > publication. I’d happily welcome it to “Geophysical Prospecting”, and I’m > sure “Geophysics” and some other journals would be equally welcoming. > > 3. If neither of the above, the challenge is to produce a proof. It’d make a > decent basis for an MSc, a pretty chapter in a PhD, and/or a worthwhile > paper. From a personal perspective, it’d also “complete” the survey design > criteria I published in 1980. > > Regards > > Alan B Reid PhD > Reid Geophysics Ltd > 7 Keymer House > Michel Grove > Eastbourne BN21 1JZ > UK > > Phone: +44 (0) 1323 735520 > Mobile: +44 (0) 781 692 4728 > Skype Name: alanbarryreid > mailto: [email protected] > web: http://www.reid-geophys.co.uk > > > ----------------------- > SEGMIN community mailing list service ([email protected]). > Change your personal options here: > https://lists.geosoft.com/mailman/options/segmin/rogah%40tpg.com.au > Colleagues can join here: https://lists.geosoft.com/mailman/listinfo/segmin > Archives: https://lists.geosoft.com/mailman/private/segmin/ > NOTE that <Reply> will reply to all members of the list.
----------------------- SEGMIN community mailing list service ([email protected]). Change your personal options here: https://lists.geosoft.com/mailman/options/segmin/archive%40mail-archive.com Colleagues can join here: https://lists.geosoft.com/mailman/listinfo/segmin Archives: https://lists.geosoft.com/mailman/private/segmin/ NOTE that <Reply> will reply to all members of the list.
