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METHODS

This page provides quick links to the pages on this site describing methods we imploy in our consulting: electrical geophysical methods with our equipment and software, field data collections with various GPS units, analysing data with statistical and geostatistical techniques, building enterprise GIS with commercial and freeware. Those tutorials are provided free of charge and we encourage anyone (you will need to register) to post comment and clarify points described here. However, paid clients are the priority in providing support for our products and consulting services.

Seven-step approach for complete near-surface resistivity survey of farmland with LandMapper

Despite numerous EC-mapping case studies conducted in many countries, only a few studies have demonstrated a complex approach to electrical geophysical site survey. In most studies only one technique of EC-mapping, either EM, GPR or four-electrode method was employed. This is understandable since most commercially available EC/ER measuring equipment operate in limited range of resistivities and depths (1-2 manufacturer-set depths are typical).

Locations

Protvino, MOS
Russia
55° 44' 34.0548" N, 37° 36' 55.4436" E
United States
42° 52' 48.8676" N, 104° 45' 56.25" W

1D Vertical Electrical Sounding (VES) with LandMapper Procedure

standard big manual VES cable set by LandviserThe technique and procedure described here can be performed with LandMapper ERM-01 or ERM-02 (set in resistivity mode). The electrode spacings provided in this example are identical to Landviser's supplied "big manual VES" cable set made to measure 16 layers of topsoil down to approximately 9 m. The worksheet for pre-set electrode spacings in such cable re-calculating measured resistivities to 1D VES profile can be downloaded as Manual 1D VES workbook (MS Excel format).

Other electrode spacings are possible for custom-made cable arrays to reach deeper profiles. For example, we developed and tested with LandMapper a 60m-long cable, measuring down to ~ 20 m for one custom hydrology project

This manual VES technique is most convenient to use with three people. Follow step-by-step instructions below. If you need further help, do not hesitate to contact Landviser, LLC @ +1-609-412-0555 or info@landviser.com. Register on our site and download 7 related publications and software!

Locations

San Antonio 29° 25' 26.8392" N, 98° 29' 37.0608" W
Dmitrov 56° 20' 39.0192" N, 37° 31' 2.5716" E

2D Dipole-Dipole Electrical Tomography with LandMapper

Manual measuring of electrical resistivity 2D cross-section is possible with LandMapper with supplied (optional) or made by user cable set.

There are two modifications of 2D cable set offered and tested by Landviser, LLC:

  1. Mobile shallow (~2 m depth) set consisted of two T-style probes (AB and MN dipoles) similar to mapping probes. The dipoles are set at 1 m size with possible separation between dipoles (wire length) no more than 5 meters (n=5).
  2. Stationary set (~ 14 m depth) where electrodes are hammered on the soil surface along the straight line at one meter distance. Electrodes are simple metal spikes/nails and is sourced locally (are NOT provided by Landviser, LLC). We supply wires with banana-plug connections to LandMapper terminals on one end and alligator clips on the other end to connect with electrodes.

Principle of measurements with both sets is the same for both cable sets and is illustrated by figure below. You can also watch instructional videos on our YouTube Channel - LandviserLLC

Location

0° 34' 51.8304" N, 71° 51' 2.1096" W

ELECTRICAL POTENTIAL (Self-Potential) MEASUREMENTS with LandMapper ERM-02

Self-potential map to detect directions of water fluxes, KievThe self-potential (SP) method was used by Fox as early as 1830 on sulphide veins in a Cornish mine, but the systematic use of the SP and electrical resistivity methods in conventional geophysics dates from about 1920 (Parasnis, 1997). The SP method is based on measuring the natural potential differences, which generally exist between any two points on the ground. These potentials are associated with electrical currents in the soil. Large potentials are generally observed over sulphide and graphite ore bodies, graphitic shale, magnetite, galena, and other electronically highly conducting minerals (usually negative). However, SP anomalies are greatly affected by local geological and topographical conditions. These effects are considered in exploration geophysics as “noise”. The electrical potential anomalies over the highly conducting rock are usually overcome these environmental “noise”, thus, the natural electrical potentials existing in soils are usually not considered in conventional geophysics.

LandMapper ERM-02, equipped with proper non-polarizing electrodes, can be used to measure such “noise” electrical potentials created in soils due to soil-forming process and water/ion movements. The electrical potentials in soils, clays, marls, and other water-saturated and unsaturated sediments can be explained by such phenomena as ionic layers, electro-filtration, pH differences, and electro-osmosis.

Another possible environmental and engineering application of self-potential method is to study subsurface water movement. Measurements of electro-filtration potentials or streaming potentials have been used in USSR to detect water leakage spots on the submerged slopes of earth dams (Semenov, 1980). The application of self-potential method to outline water fluxes in shallow subsurface of urban soils is described in (Pozdnyakova et al., 2001). The detail description of self-potential method procedure is provided in LandMapper manual.

Another important application of LandMapper ERM-02 is measuring electrical potentials between soils and plants. Electrical balance between soil and plants is important for plant health and electrical potential gradient governs water and nutrient uptake by plants. Monitoring of electrical potentials in plants and soils is a cutting-edge research topic in the leading scientific centers around the world.

Locations

Zamboanga 7° 1' 27.3612" N, 122° 11' 20.0544" E
Kiev-Pechersk Lavra Kiev 50° 24' 59.1768" N, 30° 33' 55.836" E

Setting up RES2DINV/RES3DINV (DEMO ver.) for the first time

Download DEMO 32-bit version of RES2DINV and RES3DINV from attached files below this post or download DEMO versions of RES2DINV and RES3DINV. Supplemental publications and other versions of software (legacy or 64-bit) are available for registered users from the respective folders (RES2DINV and RES3DINV) under SUPPORT/Downloads section of this website. You have to login before you can acces the Downloads repository (see more here)

Note, that you can use RES2DINV without RES3DINV, but not other way around - RES2DINV have to be installed first. This demo software has decreased functionality, but it might be enough for your research and the DEMO versions never expire.
However, if you decide to purchase software, please request a formal quote from us ASAP before contacting GEOTOMO directly, as we will meet or beat price of other dealers, but we cannot guarantee it unless you secure order from us first.

Getting started with 2D resistivity interpretation using RES2DINV

Presentation, embedded below was developed to bring users up to speed in interpretation of their resistivity data. Class for end users was conducted in Indonesia and included training on field data collection with SibER-48 using ~ 900 m long profile in Wenner-Schlumberger and pole-dipole (remote electrode) 2D tomography. On the second day users received hands-on instructions on data import into RES2DINV software, quality assurance of the data based on visual approach as well as through RMS of the interpretation model. 

General discussion about non-uniquness of the subsurface interpretation modl for 1D, 2D, and 3D representations has followed this class. 

Slides can be viewed on http://www.slideshare.net/LarisaGolovko/training-on-res2dinv-and-siber48

Formatting Array Input Data File in RES2DINV: surface electrodes for any geometry

pseudosection for 2D resistivity surveys

Example of electrodes arrangement and measurement sequence that can be used for a 2-D electrical imaging survey is shown on the left. Many different multi-electrode systems have been developed over the past 15 years using different arrangements of the cables and measurement strategies (Loke, 2011). This program is designed to invert large data sets (with about 200 to 100000 data points) collected with a system with a large number of electrodes (about 25 to 16000 electrodes). The survey is usually carried out with a system where the electrodes are arranged along a line with a constant spacing between adjacent electrodes. However, the program can also handle data sets with a non-uniform electrode spacing. RES2DINV program can be used for surveys using the Wenner, pole-pole, dipole-dipole, pole-dipole, Wenner-Schlumberger, gradient and equatorial dipole-dipole (rectangular) arrays. In addition to these common arrays, the program even supports non-conventional arrays with an almost unlimited number of possible electrode configurations (Loke et al. 2010). You can process pseudo sections with up to 16000 electrode positions and 70000 data points at a single time on a computer with 4 gigabytes (GB) of RAM. Besides normal surveys carried out with the electrodes on the ground surface, the program also supports aquatic and cross-borehole surveys.

Locations

Los Angelos 34° 3' 8.0424" N, 118° 14' 37.266" W
5° 49' 22.6488" S, 34° 58' 49.6884" E

For prices and accessories, go to Current complete catalog of Landviser LLC. Send us email, call 609-412-0555, post a comment below and we will happily provide you with a custom quote.