Adaptive techniques and other recent developments in aeromagnetic compensation

Aeromagnetic compensation, an integral part of most airborne geophysical exploration programmes, has received considerable attention throughout the last few decades. Advanced compensation systems, rooted in the original model which accounts for aircraft interference from permanent, induced, and eddy-current sources, have led to significant advances fueled by research in the areas of modelling, algorithms, sensors, performance analysis, implementation issues, and emerging applications. This paper focuses on two important recent developments. Adaptive compensation allows a fundamentally different approach by using a recursive algorithm to solve the underlying least-squares problem. The system continuously ‘learns’ from inputs, dynamically adapting solution coefficients for optimum compensation with each new set of measurements. Factors affecting its performance are analysed, and it is shown that regular use of adaptive compensation along simple trim-manoeuvre segments, much less demanding than conventional full-calibration flights at high altitude, can maintain the goodness of fit of a solution near optimal levels. Secondly, real-time dynamic compensation of on-board electronic (OBE) systems is discussed. Electric currents from avionics, hydraulics, and other instrumentation, generate interference which is not accounted for by the conventional compensation model. OBE compensation technology provides robust tolerance of such sources, simplifying both operational and data processing requirements.