Towards drone-borne gammaray mapping of soils
There is a strong growth of interest in UAV’s (Unmanned Aerial Vehicles, aka drones) as a sensor platform in geophysical surveying. Not so much to replace traditional piloted airborne surveying platforms (Figure 1). The usefulness of drones as a platform seems much more to replace walking or driving surveys. Drones are very handy tools to survey areas that cannot easily be accessed by foot or by vehicle, and that are too small to be mapped economically with traditional airborne systems. The last couple of years has shown a boom in the application of drones in geosurveying. More and more of the instrumentation used traditionally in geosurveys is becoming adapted to be used under a drone – think of magnetometers, EM systems, small GPR antennas but also geotechnical tools like LIDAR are being adapted to lightweight versions for drone use. In this article, we present another technology that in high demand for drone-borne surveying: spectral gamma-ray (Van Der Veeke et al., 2018). Mapping (natural) radioactivity for many years has been one of the standard items in the survey toolbox of a geophysicist. All rocks, soils and sediments contain tiny amounts of radioactive isotopes of potassium (40K), uranium (238U) and thorium (232Th). Their concentrations can be measured with a high degree of accuracy by spectral gamma tools and provide quantitative information on the type of soil or sediment under study.