Electrical conductivity

The resistivity data are used for identifying water bearing fracture zones and deformation zones in the bedrock, graphite and sulphide bearing horizons and clay occurrences. On the resistivity map it is also possible to distinguish highly resistive bedrock units from more conductive ones. In areas with large soil depths, the resistivity map also reflects variations in the quaternary layers.

Geophysical Airborne Measurements, Electromagnetic Fields, Slingram (detailed)

The data product Geophysical Airborne Measurements, Electromagnetic Fields, Slingram (detailed) contains point information about the real and imaginary parts of the induced (secondary) electromagnetic field from airborne measurements with Slingram systems with the aim of creating a picture of the conductivity of the soil.

Geophysical Airborne Measurements, Electromagnetic Fields, VLF (detailed)

The Geological Survey of Sweden uses these low frequency radio waves (VLF, Very Low Frequency) to gather information about the subsurface. The analysis method is based on the fact that the radio waves change character depending on the electrical properties of the ground. The receiver is mounted in an aircraft with an antenna system measuring the signal in three orthogonal directions from two VLF transmitters.

The data product Geophysical Airborne Measurements, Electromagnetic Fields, VLF (detailed) contains information about the magnetic component (H) of the electromagnetic field in the VLF band (frequency band 15-30 kHz), which varies depending on the electrical conductivity of the ground. This is calculated for coordinate points, from measurements made from aircraft at low altitude. All measurements have been made with a 3-axis antenna that measures the amplitude and phase of the magnetic vector components. The depth of the method varies with how well the ground conducts electrical current, from a couple of hundred meters in crystalline bedrock to a few tens of meters in conductive thick clay layers.

Geophysical Airborne Measurements, Apparent Resistivity as Web Map Service

The Web Map Service displays the apparent resistivity in a simplified raster with a resolution of 200 by 200 meters. The underlying information can be downloaded in the data product Geophysical Airborne Measurements, Electromagnetic Fields, VLF (detailed), then with a higher resolution.

The Web Map Services are aimed at those of you who want to use our information in your own systems or applications. The services are set up in WMS (Web Map Service) format.

https://resource.sgu.se/service/wms/130/flyggeofysik-skenbar-resistivitet

Product description for Geophysical Airborne Measurements, Apparent Resistivity (In Swedish)

Geophysical Airborne Measurements, Electromagnetic Fields, TEM, Resistivity

Helicopter-borne transient electromagnetic (TEM) measurements have been carried out on behalf of SGU in several areas in Sweden to map the soil's ability to conduct current. Data is primarily available in areas with sedimentary bedrock but also in areas with the aim of mapping soil types (for example quick clay).

Helicopter-borne TEM is an electromagnetic method where a strong current is sent out into a coil hanging below the helicopter, whereby currents in the ground are induced. Through model calculation, inversion, the resistivity distribution from the ground surface down to a certain investigation depth is obtained. Depending on geological conditions, the investigation depth at different points can vary greatly. The maximum investigation depth is generally about 200 meters but can be up to 250 meters.