Optical and Radar sensor complement each other so combined analysis of optical and radar data can provide unique information not visible in the separate images.
PLAN offers imagery from the world leaders, such as Airbus TerraSAR, in providing radar imagery data solutions from space. Images provided by optical sensors contain information about the surface layer of the imaged objects (i.e. color), while microwave images provide information about the geometric and dielectric properties of the surface (i.e. roughness) or volume (i.e. chemical composition, moisture) studied, allowing unique properties of the target to be revealed. With an active system like a SAR, images can be acquired day and night, completely independent of solar illumination.
Radar Microwaves can therefore easily penetrate clouds, and images of the surface acquired irrespective of local weather conditions. Because of their long wavelength, microwaves are able to penetrate not only clouds but also features such as soil, sand, snow (in very dry conditions) or the canopy of a forest, thus providing information about hidden features. Data acquired from slightly different orbits can be combined to produce stereo images. SAR stereo-pairs can be used to view a scene in three dimensions, very useful for geological applications, or monitoring ice movement.
SAR interferometry, a new technique that has emerged in recent years, under suitable conditions, makes possible to generate three-dimensional relief maps of the Earth’s surface. In addition, an extension of the basic technique allows the detection of very small (order of centimeters) movement of land surface features, such as Landslides and Earthquakes. Radar imagery provides powerful and rich information to both researchers and operational users working in fields such as agriculture, cartography, hydrology, forestry, oceanography and the military for ice studies, crop management, maritime surveillance and coastal and pollution monitoring.
Today, commercial radar imagery is available with resolution better than 1m and interferometric measurement (by combination of TerraSAR with Tandem-X) can achieve accuracies better than 10cm.