We are well experienced in utilising aeromagnetic surveys to detect magnetic field anomalies and analyse their source magnetizations. We plan aeromagnetic survey line spacing to have acceptable confidence in detecting anomalies of interest. However, closer line spacing may be required to support reliable inversion of a detected anomaly. For sparsely distributed anomalies of interest the cost of closer line spacing across the complete survey area may be prohibitive, particularly as much of that additional data will not help define anomalies of interest and will be redundant in their analysis. Combined UAV/drone surveys provide an alternative concept to fly an aeromagnetic survey cost-optimised to detect anomalies and then follow up with UAV/drone surveys to infill only selected areas of interest.
I present a case study of dual survey line spacing from the Sedan area northeast of Adelaide to illustrate an anomaly due to a compact, shallow source that was missed in a regional survey at a line spacing of 400 metres but was detected and reasonably defined by a survey at a line spacing of 80 metres. I use redundancy of the detailed survey data to establish survey parameters required to detect the anomaly and inversion of subsets of the data to investigate parameters required for a UAV/drone survey to reasonably define the source magnetization. These lessons can be introduced in a cost analysis of a combined-platform survey plan.