Selective Visual Attention: Computational Models and Applications

7.3 Object Detection and Recognition in Satellite Imagery

Remote sensing is a technique that observes the earth and its surface from platforms far from the earth such as satellites or space shuttles. Man-made satellites are one kind of platform which takes digital images of the earth's surface through cameras, video cameras, multispectral scanners, hyperspectral sensors, pupil diameter radar and so on. Multispectral scanners can simultaneously record the reflecting spectral signals at the same scene and form several images with different spectral bands (400–1000 nm) from visible light to invisible light (near infrared), and the technique has been extended to hyperspectral imagery with higher spectral resolution for a scene. Since optical spectral imagery includes more geological information in spectral and spatial domains, and it can be used to study earth materials and detect hidden objects. However, optical spectral imagery is often disturbed by cloud cover or by changes of sunlight, and thus it cannot work in cloudy or rainy conditions or on a dark night. The electromagnetic wave signals with lower frequency range can pass through the cloud layer and this is independent of changes of visible light intensity (it works in almost all weather conditions, day or night), so a satellite with synthetic aperture radar (SAR for short), by transmitting and receiving electromagnetic wave signals, has been developed. SAR can directly generate two-dimensional imagery with orthogonal dimensions ...