geotechnical parameters; the optimization of sensors and sources (arrays, permanent sensor deployment, embedded sensors in natural and built environments, sensor reliability, calibration, communication, power requirements, control, and data transmission); and adequate processing algorithms that reveal the inherent high gradients in stiffness, porosity, and saturation conditions in the near surface. These new techniques must address the need for high resolution compatible with engineering applications, the complementary nature of multiple geophysical methods, and the need for ground truth provided by invasive techniques.


3.5.1 Background

Remote sensing techniques involve noncontact observation, measurement, and recording from an airborne or space platform of electromagnetic energy reflected by or emitted from a target. Passive systems measure energy that is reflected or transmitted from an object on Earth’s surface back to the sensor (e.g., satellites that record visible, near-infrared and thermal infrared wavelengths), whereas active systems generate energy and record the reflection from the body that it strikes (e.g., radar). The digital images captured by remote sensing systems can be manipulated and enhanced to highlight subtle features, such as vegetation type and density, water turbidity or pollutants, lithology and mineralogy, soil type and moisture, and many more features.

Space-based remote sensing systems deployed by governments or commercial enterprises are designed to make measurements of the land, atmosphere, and oceans. Starting with the Landsat series in 1973, a variety of space-based remote sensing systems have been deployed by the United States, Russia, India, Japan, and Canada. Numerous commercial remote sensing systems are now available.

The oil exploration industry offers an example of the potential for broader application of remote sensing in solving geoengineering problems. The demand for better petroleum reservoir characterization and manage-

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