Full geological surveys and resources assessments – by GEO Resources
GEO Resources utilise high resolution panchromatic, multi-spectral stereo or tri-stereo satellite imagery with various resolutions. These include imagery sourced from Worldview, Quickbird, Geo-Eye, Ikinos and Pleiades Satellites.
In a similar fashion to the UAV survey, ortho-mosaics can be produced that enable DTM (terrain model without objects) or DSM to be created, delivering an absolute resolution and accuracy of between 2 and 8 m (depending on model suite and satellite images used). Satellite images have the advantage of providing information over hundreds of square kilometres.
- Project supervision
- Exploration programmes
- HSE audits & inspections
- Training and development
- Expert data quality control
GEO Resources can provide topographic surveys and geographic control for a range of purposes, utilising drones or unmanned aerial vehicles (UAV) for data acquisition. The area under survey, individual resolution requirements, client budget and operational purpose all determine survey accuracy requirements. Accuracy parameters range from 10 millimetres to 8 metres, and are provided using GEO Resources specialist equipment and expert surveying methods. The UAV method is becoming increasingly popular for stockpile surveys.
A pre-programmed flight is made by the UAV over the stockpile, during which the drone captures photographs, with overlapping fields of view.
The photographic data is then processed and converted to a 3D graphic interpretation. The software then conducts analysis of the stockpile volume, delivering accurate details for the client.
This is a highly accurate survey method as the UAV sees the stockpile surface in its entirety – incorporating all of the terrain features, including complex 3D shapes and slopes. This type of survey can deliver better accuracy than a terrestrial survey in many cases, simply because the entire surface is viewed and captured from above. Undulating terrain surveys will very often call for a UAV-based survey.
Use of a UAV negated the need for surveyors to enter the stockpile. As well as giving a boost to a project’s HSE credentials by separating staff from any potential risk, the data is gathered more quickly than with a ‘boots-on-the-ground’ approach.
The Phantom 3 Professional is a white copter, with four pylons (each with a rotor), a bottom-mounted camera, and landing struts. The drone measures about 23 inches from wingtip to wingtip and weighs just under 3 pounds.
LED lights at the bottom of each wing help to keep track of it in the air. Data is collected and measurement recorded using best industry practice and standards.
Magnetometers are used in geophysical surveys to detect and locate subsurface ferromagnetic (iron-bearing) mineral deposits.
GEO Resources use a Scintrex high precision cesium magnetometer (ENVI PRO), which ensures rapid collection of high quality ground magnetic data. Using the latest processing techniques, we are able to extract and interpret the maximum amount of information from the data set, giving the best results.
A combination of contouring and color shading maps (2D & 3D) are generated, using specialist interactive software, to highlight targeted anomaly patterns. These surveys have found to be useful to help delineate chromite ore bodies.
The Leica TC1202 Total Station boasts 2” angle accuracy, with a dual compensator on a V&H axis, compensating for tilt error in any direction. Leica uses the latest distance technology to take advantage of a powerful suite of on-board programs and many sensor and accuracy options, delivering optimised data reliability. This total station is used by GEO Resources across a range of surveying, engineering and construction work.
Data transfer to laptop or any data collection method is made easy with the RS-232C interface, with its on-board memory storing up to 8000 points, eliminating additional data collector costs. The unit has a detachable tribrach, making it easily and quickly manoeuvrable – meaning faster results for the client.
The resistivity of the subsurface, a material constant, is then a function of the magnitude of the current, the recorded potential difference, and the geometry of the electrode array. Depending upon the survey geometry, the data are plotted as 1-D sounding or profiling curves or in 2-D cross-sections in order to look for anomalous regions.
Resistivity measurements are associated with varying depths relative to the distance between the current and potential electrodes in the survey, and can be interpreted qualitatively and quantitatively in terms of a lithologic model of the subsurface.
Utilised across a range of environments and depths, the electrical resistivity technique of geophysical exploration is suitable for both soundings and profiling. This method is used to explore:
- Geologic structure
- Thickness of overburden
- Location of sinkholes and cavities
- Depth to freshwater-saltwater interface
- Groundwater depth
- Contamination of groundwater
- Lithology favourable for groundwater
- Detection of fractures and dikes
- Qualitative interpretation of the data is efficient and straightforward
- Multi-purpose – can be used for various purposes and depths of investigation
- Shallow investigations are fast and accurate
- Minimises field expenses
For further information on our full geological surveys and resources assessments, or to speak to a member of our expert team,
call or email GEO Resources today.
Resistivity Imaging (Tomography)
Resistivity geophysical surveys measure variations in the electrical resistivity of the ground, by applying small electric currents across arrays of ground electrodes. This technology can be used by GEO Resources to obtain images of relatively static subsurface site conditions.
The survey data is processed to produce electrical resistivity tomographs using inversion algorithms. The resistivity sections are correlated with ground interfaces such as soil and fill layers or soil-bedrock interfaces, to provide engineers with detailed information on subsurface ground conditions.
Resistivity imaging, also known as electrical resistivity tomography (ERT) is a particularly useful survey method in clayey ground, where techniques such as Ground Penetrating Radar (GPR) are less effective. The method can also help to identify transitional boundaries in subsurface layers that can be difficult to detect using other geophysical methods and is a useful tool for locating deep seated sinkholes, mine workings and detection of metallic ore bodies.
Resistivity soundings, profiles and ERT are also used to assess the geometry of aquifers and their likely water quality. These tools are particularly useful in
locating water supplies.
TOMOGRAPHY by GEO RESOURCES – Detecting the parts other geophysical methods cannot reach
- Rapid collection of data
- Ascertains likely water quality of aquifers
- Locates metallic ore sources, disused mines and sinkholes
- Advanced method of exploration – 2D and 3D surveys available
Time-Domain Electromagnetic (TDEM) Soundings
Time-Domain Electromagnetic (TDEM) soundings are widely used by GEO Resources in exploration geophysics for mapping subsurface layers. TDEM is a relatively low cost, rapid, and noninvasive reconnaissance tool to locate potential water resources.
The TDEM method is well suited to near-surface hydrological studies as it can be used to differentiate between fresh, brackish, and saline water. It is used to investigate the electrical conductivity of the subsurface through measurements of electromagnetic field over time.
The characteristics of the TDEM responses of the earth due to a pulsed primary signal from a large wire square-loop laid on the ground surface yields information about the variations of the electrical conductivity with depth.
The conductivity of soils and rocks are controlled by mineralogy, clay content, water content, salinity, and porosity. Changes in the conductivity of soils and rocks produce variations in the electromagnetic signature.
A combination of existing well water quality measurements borehole data and surface TDEM can be used to accurately map the subsurface water resources with one caveat: a signal from clay can sometimes produce a response similar to water.
TDEM surveys – conducted by GEO Resources
- Thermal : Extent of hydrothermal alteration mineralogy may be inferred
- Hydrological information such as depth to groundwater table may be determined
- Structural/Stratigraphic : Structural information gathered from TDEM data
- Lithology : Detection of rock units or geological features with contrasting apparent resistivity.
- Ore explorations
- Environmental studies
- Hydrogeological investigations
- Magnetotelluric (MT) static shift corrections
- In geothermal areas – conductive clay cap reconstructions
- Engineering studies – water sourcing, Earth layering, bedrock delineation