Similar to airborne magnetic surveys, land magnetic methods are a cost-effective technique for measuring the strength of the Earth’s magnetic field, when a high level of detail is required.
While airborne magnetic data provides superb quality and is faster to acquire, the shorter distance to the source and tighter line spacing of ground magnetic surveys provides more resolution when it is required. This is especially important for detection of shallow faulting, bedding, and other subsurface discontinuities where the presence of magnetic minerals and their associated rock types, in contrast with surrounding sedimentary rock, produces a measurable signal.
Ground gravity methods effectively measure very subtle subsurface density changes in rocks, providing very detailed information on complex settings where other methods might not satisfactorily resolve the problem. From structures containing hydrocarbons, to metal deposits, iron ore, salt domes, sediment thicknesses and hydrogeological aquifers, the size and location of a number of geological structures can be determined using this method. The fact that the gravity field intensity rapidly decreases with distance from the source means that ground methods can provide unrivalled resolution to address complex and shallow objectives, where the use of airborne is not advisable due the small size of the area of interest, or other logistic reasons. The ground gravity method also allows several configurations, geometries, and line spacings, that can be tailored to suit the needs of the survey.
GPR is a non-intrusive survey method that uses high frequency electromagnetic pulses to acquire very high-resolution data in a short time. The data can be used to rapidly produce 2D profiles (that can be integrated and presented as 3D blocks) with an appearance similar to seismic profiles, providing very detailed shallow information where the contrast of permittivity of the material allows it. It can be used to map bedrock, soils, groundwater and ice, the transition between sedimentary and metamorphic/igneous rocks, alluvial gravel beds, buried tunnels, etc; all at shallow levels (up to 200m).
