Active Systems

Active systems are those that generate their own source of radiation. The systems then record the amount of energy that is reflected back to their sensors. The advantage of active systems is that they can be used both day and night. Moreover, these systems can be used to investigate wavelengths that are supplied in small quantities by the sun (e.g. microwaves). The most common active system used for geological exploration is the synthetic aperture radar (SAR), such as RADARSAT-1.

An important feature of active radar systems is that they are sensitive to longer wavelengths than conventional optical passive systems. The microwave pulses emitted by RADARSAT-1 are capable of penetrating thick cloud covers. As a result imagery can be acquired both day and night, and irrespective of the weather conditions. Radar intensity is mainly affected by surface roughness, and is very sensitive to topographic variations. In addition to being an excellent tool for mapping exposed geological structures, RADARSAT-1 can also detect structures obscured by vegetation by mapping the topographic surface created by the treetops (“treetop geology”). Another advantage of RADARSAT-1 imagery is the availability of variable resolution and incidence angles with stereo capabilities. Future radar missions, such as RADARSAT-2, will have increased spatial resolution and polarimetric capabilities.

Example 1 – Terrain mapping and treetop geology; Canadian Foothills, Alberta
Example 2 – Lithological and structural mapping; Papua New Guinea
Example 3 – Structural mapping; Magdalena Basin, Colombia