Assessing the Frozen State of Soils Using iFrost: An Electromagnetic Induction Sensor on a UAS Platform

Effective and efficient mapping of permafrost subsurface composition at scales relevant to the design and maintenance of horizontal and vertical infrastructure has been a long-standing challenge. Of utmost utility would be the development of standoff measurement techniques that could discern at the meter to submeter spatial scale and up to 10 m into the subsurface the presence or absence of ice features. Ground-based geophysical measurement techniques, including ground penetrating radar, borehole logging, and electrical resistivity, have been used to interrogate the subsurface in permafrost terrains at the meter to kilometers scales. Airborne measurement techniques have broad applicability at the larger, kilometers to tens of kilometers scale and could support linear infrastructure development and terrain mapping. However, there is a broad need for cost effective airborne geophysical techniques to obtain high-resolution measurements of specific areas of interest. We present a frequency domain electromagnetic induction sensor weighing less than 10 pounds mounted on an unmanned aerial system capable of assessing the frozen state of soil to 10 m depth. We consider system design and motor interference as well as present a 3D model capable of identifying discrete ice inclusions on the order of 1 m in size.