A High-Speed, Light-Weight Scalar Magnetometer Bird for km Scale UAV Magnetic Surveying: On Sensor Choice, Bird Design, and Quality of Output Data

Abstract

Magnetic surveying is a widely used and cost-efficient remote sensing method for the detection of subsurface structures at all scales. Traditionally, magnetic surveying has been conducted as ground or airborne surveys, which are cheap and provide large-scale consistent data coverage, respectively. However, ground surveys are often incomplete and slow, whereas airborne surveys suffer from being inflexible, expensive and characterized by a reduced signal-to-noise ratio, due to increased sensor-to-source distance. With the rise of reliable and affordable survey-grade Unmanned Aerial Vehicles (UAVs), and the developments of light-weight magnetometers, the shortcomings of traditional magnetic surveying systems may be bypassed by a carefully designed UAV-borne magnetometer system. Here, we present a study on the development and testing of a light-weight scalar field UAV-integrated magnetometer bird system (the CMAGTRES-S100). The idea behind the CMAGTRES-S100 is the need for a high-speed and flexible system that is easily transported in the field without a car, deployable in most terrain and weather conditions, and provides high-quality scalar data in an operationally efficient manner and at ranges comparable to sub-regional scale helicopter-borne magnetic surveys. We discuss various steps in the development, including (i) choice of sensor based on sensor specifications and sensor stability tests, (ii) design considerations of the bird, (iii) operational efficiency and flexibility and (iv) output data quality. The current CMAGTRES-S100 system weighs ∼5.9 kg (including the UAV) and has an optimal surveying speed of 50 km/h. The system was tested along a complex coastal setting in Brittany, France, targeting mafic dykes and fault contacts with magnetite infill and magnetite nuggets (skarns). A 2.0 × 0.3 km area was mapped with a 10 m line-spacing by four sub-surveys (due to regulatory restrictions). The sub-surveys were completed in 3.5 h, including >2 h for remobilisation and the safety clearance of the area. A noise-level of ±0.02 nT was obtained and several of the key geological structures were mapped by the system.

A Novel Noise Reduction Method of UAV Magnetic Survey Data Based on CEEMDAN, Permutation Entropy, Correlation Coefficient and Wavelet Threshold Denoising

“…Assume a time series X= (1,5,3,4,2), the embedding dimension m is set to 3 and the time delay τ is set to 1. Three reconstructed time series can be obtained as: (1,5,3), (5,3,4), and (3,4,2). According to (16), the permutation for (1,5,3), (5,3,4), and (3,4,2) is (0,2,1), (1,2,0), and (2,0,1), respectively.…”

“…Three reconstructed time series can be obtained as: (1,5,3), (5,3,4), and (3,4,2). According to (16), the permutation for (1,5,3), (5,3,4), and (3,4,2) is (0,2,1), (1,2,0), and (2,0,1), respectively. The normalized permutation entropy can be obtained as:…”

“…Among these applications, the use of UAVs for magnetic surveys is a booming branch of research [2]. UAV magnetic surveys can cover a wider range with a higher efficiency compared with the traditional terrestrial magnetic surveys, and are also easy to operate, have a low-cost, and have a good safety profile compared with manned aircraft magnetic surveys [3]. In addition, UAV-based magnetic surveys can also be carried out in areas that are difficult to access or that would pose a potential hazard to operators (e.g., near active volcanoes), which means that some gaps in traditional magnetic surveys can now be studied [4,5].…”

The Joint UAV-Borne Magnetic Detection System and Cart-Mounted Time Domain Electromagnetic System for UXO Detection

“…Affected by the magnetization effect of the geomagnetic field, the ferromagnetic target produces an induced magnetic field, causing a local magnetic anomaly field [3]. Various types of scalar or vector magnetic field sensors are fixed on different carrier platforms, forming the handheld [11,12], helicopter-borne [13] and UAV-mounted magnetic measurement systems [14,15]. The drone-based magnetic detection system shows significant advantages in detection efficiency and spatial resolution of the magnetic data [16], which is a hot spot of current research.…”

Indoor Mapping of Magnetic Fields Using UAV Equipped with Fluxgate Magnetometer

“…The aerial data [ 56 ] also maps for subsurface structural monitoring [ 57 ]. Sometimes, the research is focused on only the visualization of the measured magnetic field data [ 58 , 59 , 60 ], often for the purposes of electromagnetic compatibility [ 61 ], using different kinds of software solutions [ 62 , 63 ] and different visualization methods involving for example, visualization using flux lines [ 64 ], volumetric display [ 65 ], or even interactive visualization methodologies [ 66 , 67 ].…”