EM-4H mounted on Аn-2

Airborne Low-Frequency Electromagnetic System EM-4H


The EM-4H installed on a light airplane or a helicopter is a cost effective conductivity mapping system well suited for

  • regional mineral exploration,
  • groundwater resource evaluation,
  • geological mapping,
  • detailed survey of potential economic deposits.

This is a frequency-domain system that combines simplicity and effectiveness of measurements with their high resolution and high effective depth. Its transmitter loop is mounted on a fuselage of an aircraft, and receiver coils are placed in a small towed bird.

System Features

EM-4H mounted on Mi-8
  • Due to low weight, low power requirements, and compact design of the system it can be installed on light helicopters and fixed-wing aircrafts with ease.
  • Nearly all functions are automated in order to make the EM-4H system very simple to operate. From our experience, it takes no more than 10-14 days to train technicians to conduct surveys confidently with EM-4H.
  • The EM-4H software includes navigation and flight planning tools that automatically directs the aircraft to a start point, develops the optimum flight path and gives real time course corrections along the survey route to the pilot through a front mounted indicator. This software coupled with the GPS receiver data provides quality of location and flight height data good enough to conduct surveys with line spacing of 50 m or less.
  • Average efficiency of surveying is about 1000 line kilometers per day.
  • EM-4H measures full response, i.e. inphase and quadrature components of the secondary field, with the accuracy about 1% for the averaging interval about 0.5 sec. This accuracy was achieved by the use of unique method of continuous transmitter-receiver geometry monitoring.
  • Wide range of fixed frequencies ensures effective penetration and good resolution in both conductive and resistive terrain.
  • To obtain stable, nearly noise-free data modern signal processors, proprietary algorithms to remove aircraft influence, and effective mathematical methods of digital filtering are used.

Practical Use

electromagnetic profile of lake Tus
The profile of saline lake Tus in Khakassia.
Specific resistance of the ground is about 100 Ohm-meters,
resistance of the water is about 0.1 Ohm-meters.

Twelve EM-4H systems have been produced for Aerogeophisica, service company NF VSEGEI, diamond mining company ALROSA, and gold mining company Amur.

Due to the achieved accuracy measured data can be converted to high-quality maps and profiles of apparent resistivity after short processing. These maps and profiles don't depend on a height and usually there is no need in any additional manual processing or filtering.


Boron-iron-ore deposit Zheleznii ridge in Chita region.
There are apparent conductivity map combined with anomaly magnetic field and outlines of main tectonic structures (for frequency 2080 Hz) and conductivity depth images along four routes
Zheleznii ridge map and CDI

System Specification

  • Waveform Frequencies: 130, 520, 2080, 8320 Hz.
  • Dipole moments: 20000, 10000, 4000, 2000 A*m2.
  • Power requirements: 900 W (33 A for 27 V).
  • Interface: RS232 or Ethernet (TCP/IP).

Weight and Dimensions

Product sheet in pdf