Requirements
Resistivity
Resistivity meters measure the electrical resistance in the soil.
Results from these surveys can be affected by both arid and water-logged soils and therefore a project of long duration may be interrupted until the soil conditions return to an acceptable condition. Resistivity can also be affected by power cables that are ‘leaking’ a charge into the soil.
This resulting in the readings of the
survey needing to be filtered which takes longer to process thus extending the time required to perform the survey, which would
result in additional costs to the client. The typical maximum depth of detection for a survey using this technique is 1.5m.
Magnetometery
Magnetometery detects fluctuations in the Earths magnetic field, but results are dependent on the amount that the soil of a site has been magnetically enhanced and also what depth the features/anomalies are situated. Typically data is retrieved on features/anomalies situated at a
maximum depth of 1.5m to 2.0m. However features with strong magnetic properties can be detected to adepth of 2.0m to 3.0m.
Magnetometer surveys are dependent on site having suitable soil composition, i.e. soils with magnetic properties. Also features/anomalies
are required to have suitably differing magnetic signatures from that of the surrounding soil.
Sites with metal fences, power cables (overhead or underground), iron pipelines will have an adverse effect on the data retrieved. Adverse weather conditions may prohibit undertaking a survey using this technique.
