{"refrec":{"BRefID":27616,"RR":"<b>Sengpiel, K.-P.</b> (1989). Results of airborne EM groundwater exploration in a desert area using the centroid depth algorithm for evaluation. <i>Natuurwet. Tijdschr. 70(1-4)</i>: 349-356","BEntID":27616,"PublicFlag":1,"CheckedFlag":0,"wosflag":0,"vabbflag":0,"RefStringPartII":". <i>Natuurwet. Tijdschr. 70(1-4)</i>: 349-356","DocTypID":8,"DocType":"Journal article","MarineFlag":0,"FreshFlag":0,"BrackishFlag":0,"TerrestrialFlag":0,"Authorstring":"Sengpiel, K.-P.","OrigTitleTranslFlag":0,"Authorstringtrunc":"Sengpiel, K.-P.","Englishabstract":"Secondary magnetic-field data from a three-frequency electromagnetic (EM) helicopter survey have been evaluated using a novel inversion technique called the centroid depth algorithm. It yields the centroid depth z* of the electric current system (induced by a dipole source) and the \"ambient\" resistivity p<sub>a</sub> at this depth, both for each transmitted frequency. It is illustrated by several examples how the true vertical resistivity distribution is approximated by the p <sub>a</sub> (z*) function. For three transmitted frequencies this function is only partially known but it can be closely represented by a spline interpolation function. The complete, although approximate, resistivity information can be represented as vertical sections along flight lines or horizontal sections at certain preselected depths.Using these techniques the three-dimensional resistivity distribution below a non-perennial river in a desert area in Pakistan is shown and compared with Schlumberger resistivity soundings and results from drilling and dug wells. Several other fresh-water deposits in salt-water-bearing environments have been delineated using this airborne EM method.","AbstractOtherLang":null,"BibLvlCode":"AS","StandardTitle":"Results of airborne EM groundwater exploration in a desert area using the centroid depth algorithm for evaluation","OrigTitleLangCode":"en","OrigTitleLangCodeExtended":"eng","OrigTitleLangID":15,"DateLastModified":{"date":"2025-07-02 08:33:14.980000","timezone_type":1,"timezone":"+00:00"},"UserAccessRight":null,"UserAccID":null,"AuthorKeywords":null,"OtherDescriptors":null,"Notes":null,"AnaPub":1989,"MonPub":null,"DateUpdate":"2022-03-15","DateCreate":"2002-09-26","SecASFANote":null,"ConfID":null,"PeerRev":1,"VlizCoreFlag":1,"WoScode":null,"VABBcode":null,"OpenAcc":0},"refs":null,"anarec":{"AnaID":27616,"PubliDate":1989,"Pagination":"349-356","XtraPublOfAnaID":null,"ISBN":null,"Volume":"70","Issue":"1-4","BRefMon":null,"BRefMonRR":null,"BRefXtra":null,"BRefXtraRR":null,"SerBRefID":43436,"SerRR":"Natuurwetenschappelijk Tijdschrift. 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