Geophysics HM

Translate This Page

For a successful completion of the survey campaign our professionals and technicians get prepared, trained and equipped with all necessary electronic instruments, ADC dataloggers and filed accessories for setting up the survey grids, testing the instrumentation and acquiring the required geophysical data. The field data acquisition follows the industry standards established for the practice of the geophysical profession at all times.

The equipment operators constantly adjust to the existing site conditions and project requirements in a safe and cautions matter while maintaining the accuracy of the measurements. Our management and professional staff encourage our field technicians and operators to adhere to the well stablished and approved mandates for all of our geoscientific projects. Common geophysical techniques used by Geophysics HM Ltd are Ground Penetrating Radar, Refraction Seismic, MASW, Induced Polarization, ERT.

Geophysics HM Ltd provide a wide variety of data acquisition for small-to-large scale geoscientific projects in Canada and internationally. The field data acquisition follows the industry standards established for the practice of the geophysical profession at all times.

Geophysical equipment are design and build for measuring the natural occurring physical fields and responses generated from the differences in the physical properties of the earth rock formations, subsurface conditions and manmade materials and phenomenon. The measured electric signal originated from the interface between two materials with different physical properties can be natural occurring, transmitted, induced, reflected and refracted. The geophysical techniques that measure the natural occurring physical fields (Magnetic, Magnetotelluric and Gravity) are named passive methods. The methodologies and instruments for measuring the subsurface responses generated or induced by man are called active techniques such electric, electromagnetic and seismic.

Collect the data in an organized and consistent manner;
Constantly check the data quality, errors, background noise and omissions;
Document the site conditions using photographs, videos, illustrations and sketches. This include notes of existing geological features, power sources, topography, location, grid and profile offsets, date, time, equipment, stationing, and operator remarks;
Check and dump the data from the equipment or data logger to a secondary digital device before leaving the site.

Electronic instrumentation, accessories (spreads, sensors, sources of signal excitation) and measuring tools are designed for deployment over different ground surfaces (topographic or man-made material surfaces) and underground conditions, environments and dimensions (1D, 2D and 3D). Most of the geophysical methods are non-intrusive, fast, inexpensive, and possess a great deal of detail when compared to other conventional exploration techniques deployed in or between boreholes. Different instruments and field accessories are brought to the site for any geophysical survey, including data loggers, communication cables, multi-wire spreads, power generators, wooden and steel stakes, measuring wheels, flags, GPS systems and radio communication equipment.

At Geophysics HM Ltd the geophysical electronics and transducers are well maintained and treated with extreme care and according to manufacturer technical specifications and recommendations to avoid bad data collection, instrumentation errors, costly repairs and survey delays.The electronic instruments and sensors are the most important parts of the geophysical data acquisition systems. They are built with delicate analog to digital converters, sensing devices, electric boards and precision moving parts. The instruments are required to perform effectively over extreme weather, terrain and working conditions.

The Structure Scan Mini XT is GSSI’s newest generation of our very popular all-in-one ground penetrating radar systems. The StructureScan Mini XT offers a 2.7 GHz antenna for superior target resolution and can reach depths up to 60 cm (24 in). This system is designed with the option for users to add accessories and tailor the unit to specific applications. With multiple modes of operation, the StructureScan Mini XT is ideal for locating rebar, conduits, post-tension cables, voids and real-time determination of concrete slab thickness.

GSSI GS Series, is a new generation of high-performance antennas targeting applications that require deeper penetration depths. The first antenna in the series is the 200 HS. This digital, wireless antenna features a 200 MHz center frequency and employs GSSI’s proprietary HyperStacking® technology. This technology improves signal to noise performance and increases depth penetration under all soil conditions. The GS Series is ideal for geophysical, geotechnical, and environmental applications that require high reliability under challenging survey conditions.

The RoadScan™ 30 system provides users with an effective tool for quickly determining pavement layers at high speeds. RoadScan is able to collect data densities not obtainable using other labor-intensive methods commonly used for pavement testing. BridgeScan™ is a complete, affordable GPR system that is an effective tool for quickly determining the condition of aging bridge decks, parking structures, balconies and other concrete structures. The system is also used to obtain accurate concrete cover depth on new structures.

The EM61-MK2A is a high sensitivity, high resolution, time domain metal detector suitable for the detection of both ferrous and non-ferrous metal. Typical target response is a single, sharply defined peak, facilitating quick and accurate determination of location. Achievable depth of detection will depend on several target characteristics, with the surface area and orientation of the target of particular importance. A single 200 litre (55 gal.) drum can be detected at depths greater than three meters.

The EM39 provides measurement of the electrical conductivity of the soil water matrix surrounding a borehole or monitoring well using the inductive electromagnetic technique. The unit employs coaxial coil geometry with an intercoil spacing of 50 cm to provide a substantial radius of exploration into the formation while maintaining excellent vertical resolution. Measurement is unaffected by conductive borehole fluid or the presence of plastic casing. The instrument operates to a maximum depth of 500 metres.

The Geode Exploration Seismograph is the most popular seismograph in the world, used by both academics and geophysical professionals. The Geode is a versatile and flexible seismograph, small and lightweight enough to pack into your suitcase, yet easily expandable if needed for full-scale 2D and 3D surveys via our intelligently designed distributed architecture. Use the Geode for reflection, refraction, MASW/MAM, or tomography surveys, as well as for more niche use cases such as earthquake, quarry blasts, or heavy equipment monitoring.

The SYSCAL R1 Plus resistivity meter is specifically designed for medium-depth exploration. It combines a power source, transmitter up to a 200W or 800Vpp output voltage, and a 2 channels receiver in a single unit; its compactness makes it an effective tool for intensive resistivity surveys. The measurement is fully automatic, controlled by a microprocessor: automatic self-potential correction, automatic ranging, digital stacking for signal enhancement, error display in case of procedure troubles.

GEM’s Overhauser Magnetometer system is a revolutionary geophysical instrument developed by GEM to offer a rugged, low power, and sensitive alternative to Proton Precession and some other alkali vapour magnetometers. GEM’s GSM-19 (Overhauser) magnetometer is a primary standard in mineral exploration and magnetic observatories. As a standard for magnetic observatories, this system has proven itself – for its high sensitivity, absolute accuracy and long life. Overhauser magnetometers are also used in archaeology, pipeline mapping, UXO detection, and other geological, geotechnical and environmental applications.

The NUMIS Poly device is a Magnetic Resonance Sounding (MRS) system for the direct detection of shallow groundwater down to 150 m of depth. NUMISPoly is a modular multi channel MRS equipment designed with units weighting 25 kg or less, making it man portable. The transmitter unit produces pulses at the Larmor frequency. The receiver units (up to 4) measure the MRS signal and the noise, after filtering, amplification and analog to digital conversion. The PC computer receives raw data, then processes, displays and stores them (including time series) for further interpretation.

The vLoc3-9800 from Vivax-Metrotech is a fully-automatic gain control, precision left/right guidance utility locator. The vLoc3-9800 is built on a new Triaxial 3D antenna architecture with highly configurable features. The vLoc3-9800 offers two passive modes and all available frequencies between 16Hz up to 200kHz. Audio and mechanical vibration alerts can also be configured by users providing warnings for shallow depth, overload, overhead cables and excessive swinging. The vLoc3-9800 can be equipped with optional Bluetooth module for GPS mapping and MLA (marker locator adapter) add-on for locating buried EM markers and TX Link for communications between receiver and transmitter. A few applications ideal for low-frequency locating is long-haul fiber lines, metropolitan loop networks, and pipeline transmission lines.

At Geophysics HM Ltd the geophysical professionals and technicians routinely perform and request the manufacturer of the field survey equipment. Instrument calibration logs and time-lapse performance tests are included in the geophysical operating procedures and provided to clients upon request.

Factory Tests, Calibration and Maintenance: To be done by the instrument manufacturer as normally stated in the equipment user manual.

Long Term Tests, Calibration and Maintenance: To be done at least once a year. The test site and instrument setup, data collection, processing and reporting should be supervised and approved by a certified Professional Senior Geophysicist. This test will be performed only in cases of equipment malfunctioning or concerns on data quality during field operations. This test will be voided if a factory test and calibration records are available for the instrument tested.

Routine Instrument Check and Maintenance: At the beginning of each month the geophysical instruments and survey systems will be checked, cleaned and maintained as required.

Pre-Survey Tests and Calibration Procedure: To be done prior survey commencement by a field technician at the survey site.

Troubleshooting: To be done routinely by a field technician during survey execution if technical problems arise from survey setup and data collection.

Calibration Report and Raw Data: The calibration reports, results and raw data acquired for the purpose of equipment calibration will be stored digitally for review and comparison. Calibrations logs will be in the form of word documents whereas the raw data and results will be presented in tables, cross-sections and plan maps. Results and recommendations derived from the calibration test should contain:

The collection of the geophysical data is carried in survey grids, profiles and stations previously established over the survey area. A variety of geophysical surveys require collecting data moving the instrument at equal intervals along straight lines above the surface (e.g. MAG, GPR). Other techniques use multi-wire lines with sensors attached at equal intervals spread in the surface along the survey path or boreholes (e.g. Seismic, ERT, Electromagnetics).

Local and geographic coordinates for the grids, profiles and stations are collected during the survey for later referencing and map creation. The grids are layout in the field using commercial measuring tapes, measuring wheels, theodolite and Global Positioning Systems.

Survey Lines

For acquiring the geophysical data it is required to have profile lines with stations positioned over the surface with paint, flags or stakes. A survey grid is formed by a combination of base lines and profile lines arranged in parallel and perpendicular pattern if required. The geophysical grid size, the number of lines and the interval between the lines will be selected based on the expected limits of investigated target along the strike direction perpendicular to the survey profiles.

For a successful survey, a few survey lines should cover the background response beyond the target extent. The grid line interval is dictated by the geophysical methodology used. In most of the cases for achieving a good survey resolution at least 2-3 lines should crosscut over the investigated target. For a proper target extent interpretation, depth and dimension estimates the survey profiles need to be positioned perpendicular to the longest axis of the expected target.

At Geophysics HM Ltd the quality of the geophysical data is the heart of our investigations. The control is done on all stages of the project execution, starting from the survey planning, data collection, processing, inversions and interpretation. Data quality is a top priority from the survey beginning until the end when thereport is completed.

Data is constantly monitored as a survey progresses to ensure that equipment is functional, the correct equipment and parameters are being used, and that the data is of sufficient quality to ensure meaningful processing and interpretation. Based on these preliminary observations, modifications can be made to the survey plan if the client wishes to focus on particular features that become apparent as data is collected. Quality assurance takes place before a survey begins. The geological and geophysical responses are considered and modelled prior to surveying if required. Based on the objective of the survey, the correct equipment and geophysical method will be selected to ensure optimal results are obtained.

Data Storage

At the end of each working day the acquired geophysical data is dumped to a field processing computer and reviewed for quality assessment. If the data is not of adequate quality for data inversion and interpretation a reacquisition or modification of the survey methodology is recommended.

Site Documentation

Site documentation is done by the means of written notes, audio and video records, photographs or sketching. Photographs showing the geophysical instrument layout and site conditions at the time of the survey should be included in the digital archive. Annotations of the geophysical parameters and site conditions should be available in the filed notes supplied along with the geophysical report. Documents and sketches illustrating the terrain conditions, weather, obstructions, survey grid layout, reference positioning, sources of noise and machinery within the survey area at the time of the survey should be provided

Geophysics HM

Geophysics HM Ltd

DATA ACQUISITION

Geophysical Instruments

Instrument Calibration

Survey Grid Setup

Survey Lines

Profile Stationing

Reconnaissance Geophysical Surveys

Detailed Geophysical Surveys

Quality Assurance & Control

Data Storage

Site Documentation

Geophysics HM Ltd