Drone Magnetic Surveys

SURVEYS TO SUPPORT GEOLOGICAL MAPPING PROJECTS

Decoors offers drone mag surveys as a powerful and efficient tool to support geological mapping projects. The next mines will be discovered in areas under cover. Large areas of the central Cordillera are hidden under glacial cover where bedrock outcrop is often scarce, and although magnetite-bearing glacial deposits and fluvial deposits may produce distinct magnetic anomalies, they are generally small, recognizable for what they are, and of little concern in mapping bedrock. Drone magnetic data can image the internal fabrics of bedrock buried beneath tens - and even hundreds - of meters of bedrock, providing crucial aid to geological mapping.

Our drone-based magnetic surveys record the intensity of the Earth's total magnetic field, measured at a magnetometer sensor attached to the drone. The results are used to produce drone magnetic maps that show the spatial distribution and relative abundance of magnetic minerals in the upper levels of the Earth's crust.

Our experienced team can fly approximately 50-100 line-kms of drone magnetics per day, depending on the terrain and access. The drone magnetic surveys can be flown at anywhere from 15 m - 100 m above ground level (AGL). An accurate Digital Surface Model (DSM) allows for lower elevation flying. If no DSM is available from the client, the Canadian Digital Elevation Model (CDEM) is used. This model often has a vertical accuracy between 4 - 30 m.

Test flights are flown in the survey areas in order to decide on the flying height of the drone. For example, with CDEM and tall (25 m) trees, a height of 60 m will likely be decided on. If there is steep topography (ravines / cliffs) as well, a height of 75 - 100 m may be used.

We provide daily updates on all surveys with preliminary results processed nightly while in the field. The team is experienced with >1,500 line-km flown within B.C. Final results include maps of the total magnetics (TMI), residual magnetics (RMI), first vertical derivative (FVD), tilt derivative (TDR), and analytic signal (AS).

Magnetic Maps

The images and other characteristics of the magnetic field are used to map basement units beneath Tertiary volcanic cover, revise contacts, identify the lithological subunits of geological units, suggest internal subdivision of units, discriminate between successions of volcanic rocks, extend the distribution of basement units, outline unmapped intrusions, map faults and highlight magnetic horizons within sedimentary, volcanic, and metamorphic assemblages.

Faults in aeromagnetic maps are commonly expressed as linear negative anomalies, linear belts of steep gradients, or by offsets of anomalies. The negative anomalies are related to oxidization of magnetite to hematite in the fault zone, and resultant significant reduction in magnetic susceptibility. Faults based on magnetic images significantly amplify the extent of faulting across the entire survey area compared with the more limited picture of faulting derived from basement bedrock windows through volcanic and glacial cover.

Geological framework revealed through images of various derivatives of the magnetic field provides an enhanced 'road map' that can lead to more effective mineral exploration.

  • The line spacing should be greater than the distance between the drone and the ground - otherwise you’re over sampling.

  • Short answer: Deep.

  • We fly our drone at 10 m/s. At this rate, we can easily cover 50 line-km in one day of flying. With same day turnaround on results, there’s nothing quicker.