ATV-mode GPR and EM Surveys
ATV-mode GPR and EM Surveys are designed to acquire as much high quality data as possible in the least amount of time and with the least amount of effort. The GPR instrument typically operates at 100 MHz whereas the EM34-3 instrument is usually high powered and set at 20-metres inter-coil spacing. Where the walking-mode would require two operators, ATV-mode surveys are done with one. The method also allows the surveys to be carried out over ground that might be too difficult or dangerous to traverse by foot.
Snowmobile-mode Cesium Magnetometer Surveys:
We pre-program navigation track-lines – no existing grid is needed.
Readings are positionally or time triggered, typically 3-metre stations or 10 times per second.
‘Ruggedized’ navigation computer also records GPS and geophysical data – seamless.
Survey speeds 2 m to 5 m per second in rough terrain – faster over fields and flat areas.
GPS antenna located at front of sleigh or cart, magnetometer located at back of sled/cart.
We post-process for Layback and Latency using in-house software.
Operational in exceptionally rough terrain, boulder fields, etc. and in severe cold.
Capable of collecting gradient magnetics data by adding sensors.
Snowmobile-mode ground-based data are technically superior to any form of airborne data.
Base Station Magnetometer System:
Magnetometer readings at 0.5s or 1s intervals.
At least 2 base stations running for quality control and duplication in case one fails.
Base stations are ‘leap-frogged’ along the survey area to keep as close to survey area as possible – important for best precision in the arctic.
Magnetometer readings linked to GPS time.
Snowmobile-mode GPR Surveys
GPR setup is mounted in a standard plastic snowmobile sleigh.
A large counter wheel extends from behind to trigger readings.
Snowmobile-mode IMAGEM Surveys
The IMAGEM system is a state-of-the-art high resolution time-domain system that is capable of recording 200 channels of on- and off-time EM measurements.
Approximately 700 amps are transmitted through a single-turn and highly portable platform. This system, which is based on airborne survey designs, replaces 50-m and less inter-coil MaxMin/Promis readings. The fixed receiver and transmitter configuration provides data that are easier to interpet particularly in variable/rough topography. Readings are collected at less than 1-second intervals for much higher resolution than MaxMin or Promis surveys.
Time constants can be calculated and the data can be imported to modeling software such as Maxwell.
The IMAGEM system is in high demand for gold exploration where high precision is required. ClearView continues to apply it for walking-mode surveys and dual cesium-magnetics & electromagnetic snowmobile-mode surveys in the arctic.
All data are processed and plotted in the field using Geosoft and proprietary in-house software.
Sometimes its required to scan the wall-faces using various methods such as GPR and Radiodetection to image the concrete. Instruments such as Sensors & Software Conquest 100 can map minor features such as rebar to around 1 metre depth. Higher frequencies can ‘see’ even deeper with lower resolution.
At other times several instruments are pulled behind a boat or kayak to scan for submerged objects and bathymetry.
Large diameter tunnels need to be scanned from inside to determine their integrity and to locate features such as drill holes meant to intersect the tunnel at regular intervals such as for outfall projects. GPR instruments can be operated by certified divers and for large outfall projects using man-lifts and portable hydraulic lifts.