Remote Sensing Analysis
Remote sensing refers to technologies for gathering visual information or other data about a site from the air or from space. Remote sensing includes familiar techniques such as aerial photo analysis, as well as novel technologies such as synthetic aperture radar interferometry (InSAR). Aerial photography is available for most areas, with coverage often extending back to the 1920s; decades of satellite data is also available for most areas of the Earth at various wavelength bands and resolutions. Exponent has expertise in the selection and analysis of remote sensing data for a wide variety of real-world applications.
Many different portions of the electromagnetic spectrum have been exploited to image the Earth. Data collected in different wavelengths can provide complementary data about a site. Visual light, infrared wavelengths, and radar wavelengths have all been exploited for remote sensing purposes.
Data and images collected in visual wavelengths are among our most useful remote sensing tools. Historical aerial photos are invaluable for observing changes in land use and development over time. Aerial photos of historical floods and landslides are useful in delineating floodplains and in determining limits of slope instability. Satellite images permit the study of large areas, such as the Iraqi marshlands shown below. Aircraft-mounted laser technology (LiDAR) allows rapid digital terrain mapping over wide areas.
Because live vegetation reflects infrared wavelengths, aerial photos sensitive to infrared light are useful to delineate forest health, the limits of burn areas and the level of recovery from forest fires. They also show vegetation lineaments related to faults or buried utilities.
Radar wavelengths are very long relative to visible wavelengths. Imaging radar can “see” at night and through clouds. InSAR satellite radar technology provides high precision data on vertical ground movements. Archived data dating back to 1992 permit observation of subtle to severe changes in ground surface levels caused by land subsidence, landslides, or earthquakes.