Over the last 25 years, there has been a revolutionary change in the resistivity (and IP) surveying method. Until the early 1990's, the resistivity method has been used as a one-dimensional (1D) tool where quantitative modelling was confined to simple horizontal layers which are not sufficiently accurate for complex geological environments. However due to recent developments in field equipment design, interpretation software and microcomputer technology, two-dimensional (2D) and three-dimensional (3D) surveys are now practical geophysical exploration tools for environmental, engineering and mineral exploration studies. A recent development is 4-D time-lapse surveys.

Over the last 20 years, there has been an explosive growth in the number of commercial multi-electrode resistivity meter systems for electrical imaging surveys sold by companies in Europe, North America and Asia. A set of free lecture notes (Spanish version aso available) which cover a number of practical aspects of 2D and 3D electrical imaging surveys, including field methodology and data interpretation, is available in the 'Downloads' page of this website.

The second development that has made 2D and 3D electrical imaging surveys practical tools is fast interpretation software that can be used on commonly available Windows based microcomputers. At this site, you can download working demo versions of the RES2DINV and RES3DINV inversion software. The demo versions have some limitations, but you can use them to invert most common resistivity and IP data sets. For current RES2DINV and RES3DINV users, you can update the software by just downloading the same files.

RES2DINV is the 2D resistivity and IP inversion software. Besides normal land surface surveys, it also supports underwater and cross-borehole surveys. In addition to the standard Wenner (alpha, beta, gamma), Wenner-Schlumberger, pole-pole, pole-dipole, inline dipole-dipole, equatorial dipole-dipole arrays; it also supports non-conventional electrode arrangements. The program supports survey lines with up to 16000 electrodes and 27000 data points. Multicore CPU support is now available in RES2DINVx64.

RES3DINV is the 3D resistivity and IP inversion software, and it is probably the first widely available commercial software of this type. 3D surveys are more time-consuming and expensive to carry out, but could be useful for very complex geological situations. To reduce costs to the user, RES3DINV is sold as a combined package with RES2DINV which costs only about 25% more than the RES2DINV program alone. It supports surveys with up to about 10000 electrodes and 150000 data points. It is probably more than an order of magnitude faster than some other commercially available 3D inversion software. In addition to surveys with a traditional rectangular grid of electrodes, it also supports surveys with trapezoidal grids and even arbitrary electrodes arrangements which is common in rugged and/or forested areas. It now supports parallel calculations on multi-core CPUs that significantly reduces the inversion time for very large survey grids. On a modern quad-core based microcomputer, the data inversion takes less than a minute for small surveys with 200 electrodes in a flat area, to a day for extermely large surveys with with thousands of electrodes in rugged terrain. Support for mult-core CPUs is now available with RES3DINVx64.

Dr. M.H.Loke, the developer of the RES2DINV and RES3DINV software, obtained a P.hD. from the School of Earth Sciences, The University of Birmingham in 1994 under the supervision of Dr. R.D.Barker. He is the Director (Software Development and Technical Support) of Geotomo Software Sdn Bhd. The company has many clients worldwide in academic institutions, engineering and environmental survey, groundwater and mineral exploration companies. His present research interests are in fast 2D and 3D inversion methods for geoelectrical data, optimisation of electrode arrays for 2D and 3D surveys, time-lapse inversion techniques, fast numerical methods and applications of parallel programming techniques in geophysical modelling. He is a member of the editorial board of the Journal of Applied Geophysics and Near Surface Geophysics, and also an invited peer reviewer for the UK Times and QS World University Ranking systems. He received the SEG-EEGS Frank Frischknecht Leadership Award in March 2019 at the SAGEEP conference in Portland, Oregon, USA. For a more detailed biography, including a list of publications, please download the following pdf file. M.H Loke Biography



Company History and Personnel

Zero longitude, London, 2000

Almost zero latitude, Singapore, 2002


Manly, Down Under, 2003

Prehistoric Forest, WA, 2006

Company Guard Dog, Penang, 2009

A home away from home. Kardinya, WA, 2013 (M.H.Loke,Naoko,Tania,Thaddeus,Thomas,Y.Gan)

Transylvania, 2019


EEGS, FastTimes 2019, 24(1)

Some Workshops

Connecticut, 2001

Bangkok, 2004

Saskatoon, 2007

Yogyakarta, 2018

Kuala Lumpur, 2019


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