Introduction

Welcome to the Exploration Geophysics Special Edition for the 7th International Workshop in Airborne Electromagnetics (AEM 2018) held at the historic Hotel KoldingFjord, southern Jutland, Denmark. The conference followed on from the previous workshop on AEM held in South Africa (AEM 2013). The event was organised by the Hydrogeophysics Group of Aarhus University and chaired by the Organising Committee consisting of Professor Esben Auken, Associate Professor Anders Christiansen, Jesper Pedersen, and Karen Dalsgaard. Assisted by the Scientific Committee (Esben Auken, Anders Vest Christiansen, Gianluca Fiandaca, Hongzhu Cai, Andreas Aspmo Pfaffhuber, Jared Abraham, Aaron Davis, Paul Bedrosian, Mehrdad Bastani, Jan Gunnink, Pierre-Alexandre Reninger, Bernhard Siemon, Yusen Cooper, and Vikas Baranwal), the Committee selected over 90papers andmanyposters for presentationover a 3-day period in June 2018. As is traditional at the closing of the AEM conferences, the location of the next International Workshop will be held in Australia. We hope to see you there. Based on the success of the previous conference on airborne electromagnetics, I decided to punish myself once again by approaching the Organising Committee of AEM 2018 and offer my service as an organiser for another special issue in ExplorationGeophysics, the journal of the Australian Society of Exploration Geophysicists. A Special Edition Committee was formed, headed by Dr Mark Lackie (Senior Lecturer inGeophysics, Department of Earth and Planetary Sciences, Macquarie University Australia; and ExplorationGeophysics Editor-in-Chief), Dr Aaron Davis (CSIRO, Australia), Dr Anders Vest Christiansen (Aarhus University, Denmark), Dr Andi Pfaffhuber (NGI, Norway), and Camilla Sørensen (SkyTEM, Denmark). Together, the Committee handled reviews and revisions for the 17 submitted papers. Theeditionhasbeena long-timecomingbut is hopefully worth the wait. Many of the papers have already been published online, but this is the first time they are collected together in print. We have papers covering recent advances in software and inversion, data processing, induced polarisation (IP), and case histories of applying airborne electromagnetics to geophysical problems. Doug Oldenburg, Lindsey Heagy, Seogi Kang, and Rowan Crockett present a compelling case for opensource 3D modelling software and how sharing codes and ideas will promote the industry, make it more efficient, and allow us to solvemore complicated problems (Oldenburg et al. 2019). This is supported in a companion paper by the same authors, but in a different order in Lindsey Heagy’s paper on simulations and inversions (Heagy et al. 2019). Modelling in three dimensions will become more important, as shown by Xiuyan Ren, Jim Macnae, and Lachlan Hennesey in their paper that compares voxelated 3D inversions to stitched 1D modelling codes (Ren, Macnae, and Hennessy 2019). The complexity of 3D models can be daunting, and choices need to be made for the algorithm and meshing method. Carsten Scholl and Frederico Miorelli choose to use vertically unstructured grids in the Otze inversion codes (Scholl and Miorelli 2019). Hossein Ali Ghari, Malte Voge,Mehrdad Bastani, Andi Pfaffhuber, and Behrooz Oskool show there is still merit in applying oneand two-dimensionalmodels for inversion of AEM data by presenting finite element modelling on unstructured triangular meshes (Ghari et al. 2019). Modelling in one dimension is not obsolete as is shown in Evgeny Karshakov’s paper onmodelling using extended Kalman filters. His results show that Kalman inversion modelling can converge rapidly to realistic results (Karshakov 2019). Even though inversions may be the final tool that a geophysicist uses at the end of the survey, it is sometimes appropriate to use faster techniques to give insight into AEM data. This is shown by José Martínez, Richard Smith, and Danilo Díaz in their paper that discusses time constants in mineral exploration survey data (Martínez, Smith, and Vázquez 2019). After investigating AEM data for tau maps, geophysicists may wish to process their data prior to further inspection and inversion. Pierre-Alaxandre Reninger, Guillaume Martelet, José Perrin, and Marc Dumont discuss