Buffer for 5 models. Resistivity and IP data quality control, denoising and editing data module, EM removing. A set of tools for mathematical modeling of geoelectrical section. Additional tools for gravity, magnetic and self potential forward modeling and joint inversion. Number of the resistivity and IP inversion algorithms : smooth, focusing, robust, block. Setting the reference model for the inversion.
Suppressing of the noise component during inversion robust reweighting. Setting of limits for models parameters, inserting of a priori geological boundaries and borehole data to inversion. Assignment of weights for datum records. Editor of measurements.
Estimation of results quality based on sensitivity matrix analysis. Calculation of sensitivity, quality and DOI index. Cutting of the model edges : by angle or sensitivity level. Number of variants for data, model and apriori information visualization.
Ability to set a semi transparent background for the resistivity section geological, seismic sections. Three-dimensional visualization of the geoelectric sections along arbitrary system profiles. Maps slices of parameters for various depths. Geological sections editor and borehole columns editor. Titled boreholes. Inversion results are output into tabular ASCII files, which can be contoured and displayed with general purpose plotting packages.
Two plotting program drivers are included. One for creating GeoSoft plots of inversion results and one for creating plots using Golden Software's Surfer for Windows. Array type options are either Dipole-Dipole or Pole-Dipole.
Dipole lengths are shown both in terms of station numbers and length units of m or ft. Station numbers represent distance along line, but may not be scaled to directly indicate length units. One to three dispersions may be used in the inversion model, although one is usually sufficient, particularly when using the Zonge model.
Two Cole-Cole dispersions may be required to fit double peak spectra, but the Zonge model can match double peak spectra with a single dispersion. On rare occasions it may take three Cole-Cole dispersions to fit some spectral curves.
Screen plots may be exported to the Windows Print Manager, to Windows metafiles wmf , to portable network graphics png raster image files, to Surfer script and data files or to Oasis montaj control and data files. Output files are given the same filename stem as the source inversion model file, plus a suffix characterizing the plot number, 1 or 2.
By default resistivity inversion results are shown on plot 1 and IP results on plot 2, but resistivity and IP plot panels can be combined within a single plot. Plots may be viewed on screen or exported for hardcopy. Modsect can generate script and data files for use with Surfer v6 or v7. GX will turn into finished plots. Modsect also exports plots directly to the Windows Printer Manger, windows metafiles wmf or portable network graphics png raster image files.
A Geometrics OhmMappaer is a capacitance coupled resistivity instrument that is dragged across the ground. There is picture above of the capacitance coupled array. The spacing between the transmitter and the receiver and the lengths of the transmitter and receiver arrays are varied to obtain different depths of penetration. This equipment can be pulled behind a vehicle and integrated with DGPS to make maps. You may also want to consider using a Geonics EM, the EM38 is an electromagnetic terrain conductivity meter that measures apparent conductivity.
Apparent conductivity is the inverse of apparent resistivity. Geonics data acquisition software is also able to record DGPS. The time of year can make a difference, especially if there are noticeable variations in the moisture of the soil. Heavy rains and spring thaws may saturate the soil. This is not necessarily a bad thing. Generally, the deeper you penetrate the less effect the near surface material has on your apparent resistivity measurements. Contact resistance plays an important part in measuring soil resistivity or rock resistivity.
Others state that the contact resistance should be less than , , or 10, ohms. These are all good suggestions, unless the soil or rock has a unit resistivity greater than these resistivity values. In any case, if the instrument is working properly I think it is best to keep the contact resistance as low as possible.
Geophysicists often use water, saltwater, and other electrically conductive liquids to reduce the resistance between the electrode and the ground. One manufacture states that laying temporary electrodes like metal ground mats or coiled chains with water poured over them may yield desirable results.
The idea is that there is more surface area in contact with the ground, than with a spike. This may not be a bad idea for electrodes spaced far apart. One may need to do some preliminary testing to determine how far the electrodes need to be spaced to avoid acquiring erroneous values. Megger makes many different products and earth resistivity testers.
They point out that the actual electrode voltage depends on transmitted current and ground resistivity. The total output power is W. While the two markets overlap, the SuperSting earth resistivity system can provide a substantially greater amount of power, when needed. Could you recommend your most suitable electrical resistivity system.
We need the gear to be shipped to Labrador, Canada to arrive ….. In the geophysical market, many of the multi-electrode earth resistivity systems utilize 56 electrodes. I believe that to get approximately 50 m of penetration over approximately half the length of a 56 electrode dipole-dipole resistivity array one would likely need to use a 10 m electrode spacing. In contrast, I believe that an 84 electrode AGI SuperSting 8 channel earth resistivity system with a dipole-dipole array and 5.
Both systems provide less coverage at depth when a Wenner array is used. However, the 84 electrode system with 5. This detail can be used to better map lateral and vertical variations that are beneficial to the inversion process. In my opinion, the more detail you have from above your target depth the more likely the earth resistivity model will reflect known conditions at depth. As with any geophysical survey certain factors determine whether or not you will get desirable results.
In this case, earth resistivity methods or soil resistivity methods do not yield unique results and the depth of penetration is dependent on the true unit resistivities and thickness. Earth Image is easy to use and is useful for correcting the geometry, splicing data, editing the data, and creating models.
Res2DInv is an excellent software package. The SuperSting administration software, which is used to program the SuperSting, would assist you with designing your multi-electrode resistivity survey and confirming my above comments. Geophysical electrical resistivity methods work well for finding sand and gravel. Please tell me more about the geology and where is the water table? Electrical resistivity methods often work well for mapping sand and gravel.
You need a large enough deposit to detect and it must have an unit resistivity that is different from the adjacent clay. If the sand and gravel is saturated it will be less resistive than if the sand and gravel was unsaturated. If the water table is below the top of rock, the overburden generally a constant thickness, and the rock is more or less homogeneous then decreases in apparent conductivity may correlate well to areas with less clay minerals. Areas with lower apparent conductivity would likely be of interest.
Multi-electrode electrical resistivity survey lines over areas of interest would provide greater detail. A SuperSting 84 electrode system could assist with determining variability within the sand and gravel deposit, the thickness, and the lateral extent.
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