The tTEM system

Background
 

The tTEM system is a ground based transient electromagnetic method giving a full 3D mapping of the subsurface. The system covers the depth range 0 - 70 m with a distance between soundings of 3 – 4 m. Typical distances between lines are 10 –20m.

 

The system is fast to deploy and easily managed by a field crew of two persons. The receiver and transmitter system is towed by an ATV. Sledge runners make it possible to run it on even rough farm fields.

Papers by the HydroGeophysics Group of Aarhus University

White paper

tTEM white paper - download

Article 

Auken, E., N. Foged, J. J. Larsen, K. V. T. Lassen, P. K. Maurya, S. M. Dath, and T. Eiskjær, 2018, tTEM – a Towed TEM system for Detailed 3D Imaging of the Top 70 meters of the Subsurface, Geophysics. download

Report

Aarhus Test-site and reference model report - download

 

Platform specifications

The transmitter platform carries the 2 x 4 m transmitter coil.

Distance between sledge runners is approx. 800 mm and the width of the runners is 50 mm. The runners are approx. 90 cm long and they are designed in a resistant rubber material good for surveying several thousand kilometres.

 

The platforms are built in non-conductive material, primary fiberglass and are towed by and all-terrain vehicle.

 

Transmitter and receiver specifications
 

The receiver supports recording of data from GPS's mounted on the Transmitter platform. System output data are fully compatible with the Aarhus Workbench tTEM modules for data processing and inversion.
 

The following table lists key parameters of the system in 50 Hz operation. Slight modifications to the measurement cycle are made when operating in a 60 Hz environment.

 

Parameters marked by * depend on the system design. It can be changed by the user

 

System software and computer

The system comes with a GIS based navigation system supporting all ordinary GIS formats. Data are stored in binary data file formats. GPS and auxiliary data are stored in ASCII files.

 

The system computer runs Windows 10 and has an SSD disk, 4 cores and 8 Gbyte of memory. The system has WiFi access point and support for 4G network (SIM card not supplied)

 

Data are off-loaded either using a cloud service or by Wi-Fi.

A field tablet is delivered with the system. Charger for standard 12 V power from the ATV is also provided.

 

System calibration

System calibration factors and results of field-testing at the Aarhus Test site are provided with the system.

Low pass filters rejecting 50 Hz and 60 Hz powerline harmonic and vibration noise are delivered in Aarhus Workbench import format. Other filters can be designed upon request.

 

 

Delivery and training

The system is delivered disassembled, in sturdy, reusable crates suitable for repeated domestic and international shipping.

 

3 days of hands-on training are provided and cover system assembly, disassembly, field operation, and data processing and inversion at a location selected by buyer. Expenses for hotel, airfare, and land transport is covered by buyer.

 

Optional item

Current ramp suitcase
 

A current ramp suitcase is used for measuring and monitoring the transmitter waveform, ramps, and calibration of the tTEM system. The suitcase includes a Matlab program for visualization and integration of the waveforms, and calibration to test site models.

The specifications for the current ramp suitcase are the following:

  • PC with Win10, WiFi, remote desktop, SSD drive

  • 2 channels Picoscop, 16 bit

  • 30 kHz current probe and > 1MHz pickup coil

  • Trigger booster for trig on the front gate TTL signal

  • 12 V TIB battery and charger

  • Specifications for the Matlab program for calibration of the tTEM system and calculation of the current turn-on and turn-off ramps.

  • Integration of current time derivative from the pickup coil

  • Calibration to test-site model. Includes a limited version of the AarhusInv inversion code.

Prices for rental of buying a tTEM system

 

Contact us for quotes at sales@aarhusgeosoftware.dk

 
 
 
 
 
 

© 2019 by Aarhus GeoSoftware

Skolegade 21, 1

8000 Aarhus C, Denmark

VAT: DK37108472

Bank: Jutlander Bank. Reg. no.:8139

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