Using a transverse marine gradiometer (TVG) as submarine pipeline location tool

In this paper we present a method and case study of locating a submarine gas pipeline using a pair of marine magnetometers in transverse configuration. The targets of the survey were a 12" main gas pipeline and a 4" return condensate line located in San-Francisco bay near Ryer Island / port Chicago. The equipment used was a “Geometrics” Transverse Gradiometer (TVG) which consists of two quantum magnetometers operating at a 10 Hz rate. Use of two magnetic sensors allowed for computing the Quasi-Analytic Signal (QAS), which greatly simplifies the anomaly signature presentation. Maps of the survey along with an estimated depth of the transect relative to the sea bottom are presented.