Magnetic Gradient Arrays for Marine UXO Surveys – Change is Good!

Abstract

Summary Magnetic gradient surveys measure the rate of change of the earth’s magnetic field between two or more locations. In this paper we demonstrate some of the benefits of collecting and using magnetic gradient data for locating ferrous targets such as unexploded ordnance (UXO) or explosive remnants of war (ERW) in marine environments, with the aim to reduce costs and provide quality survey results. The incremental survey cost is very reasonable to add multiple sensors to a single sensor survey system, thus creating gradient arrays with several sensors. There are a number of benefits to such array systems, such as maximising coverage of the survey area, more reliable target or anomaly picking and improved modelling and analysis results of selected target anomalies. In areas with sparse survey lines, gradient array data can yield much more accurate target location information than single sensor data. Using gradient array data yields superior results and higher confidence in the geophysical interpretation. This helps to reduce the number of anomalies or targets that are potential UXO and need to be investigated, saving significant time and money.