Geophysics Services


Electrical methods measure subsurface electrical resistivity (inverse of conductivity). This is a function of soil and rock physical and mineralogical properties and chemistry of pore fluids. Electrical resistivity measurements are completed when electrical current is induced into the ground through an array of electrodes. The electrode rays are expended to increase depth and the electrical readings are recorded using an electrical resistivity instrument. PUMA uses electrical resistivity tomography (ERT) which used arrays of multiple electrodes to produce 2D and 3D tomographic images of the subsurface. Additionally Collier utilizes other electrical methods such as inverse polarization (IP) and spontaneous (SP) to characterize subsurface conditions.




Example Electrical Resistivity Tomographic Profile



Typical Applications of Electrical Methods
  • Soil & bedrock lithology

  • Contaminant plumes

  • Lateral & vertical variations

  • Aquifer characterization

  • Water table depth

  • Bedrock topography

  • Fractures, fault, & karst mapping

  • Dam and levee assessment

  • Corrosion Assessment

  • Grounding Surveys

  • Marine applications

  • 2D and 3D Imaging




Magnetic methods measure the earth’s magnetic field and anomalies caused by naturally occurring and manmade ferrous materials. Theoretical models can be used to approximate size, depth, shape, and composition of various targets. Collier utilizes magnetic methods on a variety of engineering and environmental applications including drone-based magnetometer systems.



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Drone-based magnetometer system mapping detection Iron-Ore Reserve



Typical Applications of Magnetic Methods
  • Mineral Mining Reserves

  • Buried metal objects

  • Ordnance UXO

  • Utility mapping and detection

  • Clearing of borehole locations

  • Abandoned wells

  • Faults and structure

  • Archeology



Ground Penetrating Radar (GPR)

GPR methods measure the changes in the propagation of electromagnetic energy in the ground to produce an image of subsurface conditions. The GPR signal is reflected when the electrical properties of the subsurface changes. A transmitting and receiving antenna are used to induce the signal and record the reflected data. The GPR antenna is pulled by hand or vehicle and can be viewed in real time. Data is collected digitally and be collected and processed to produce 2-D and 3-D images of the subsurface. Collier utilizes GPR on a variety of engineering and environmental applications.




Example Section of a GPR Line with Interpretations



Typical Applications of GPR Methods
  • Buried objects (drums, USTs)

  • Utility mapping and detection

  • Clearing of boring locations

  • Concrete and rebar assessment

  • Voids

  • Subsurface structures

  • Waste pits, trenches

  • Fractures, faults, & karst

  • Archeology

  • Forensics