We describe the main properties of the EQUATOR airborne geophysical system and how
the system can be employed to solve some engineering and environmental problems. To date, the
EQUATOR system has been used for groundwater search in 2014 and 2015 in Siberia. The name
‘‘EQUATOR’’ originates from the intention to EQUATE, or to balance time and frequency
domain approaches in airborne electromagnetics, which is why the system was originally
designed. To the best of our knowledge, EQUATOR is the only system to collect
electromagnetic data both in time and in frequency domains. We further explain the difference
between the two methods on some numerical and field examples. Also we describe some
advantages of their coupling. In particular, by virtue of our approach, a numerically more robust
solution of the one-dimensional electromagnetic inverse problem may be achieved. The recorded
full-time measurements are further converted to in-phase, quadrature and off-time responses, as
opposed to standard frequency or time domain solutions, which have been widely adapted within
the industry. When inverting the data, our main focus is within the top 100 m of the Earth, which
are the most relevant for engineering and environmental studies. We emphasize that a combined
use of frequency and time domain data gives more detailed information about geological
structures in the near-surface. As an example, we present some case studies obtained over a
platform (Siberia) and a crystalline shield (Western Africa) setting. We further suggest using
these results in such near-surface studies as sediment thickness estimation, soil state analysis,
groundwater search, and geological structural analysis.