ABSTRACT
Earth-based remote sensing involves the collection of information regarding land, water, and atmospheric properties from above the Earth’s surface with cameras and other recording instruments. Airborne and satellite imagery are major data sources that are used to classify the Earth’s land and water resources. When mapping wetland extent, the purpose of using these data is to identify, delineate, classify, and display the boundaries of wetlands and calculate their distribution across the landscape. Aerial photography has its origins in the late 1800s when pictures of Petit Bicêtre, France, and Boston, Massachusetts, were taken from hot air balloons (Colwell 1997). Images were rst captured by cameras on black-and-white (BW) lm, then on true color or color infrared (CIR) lm, and later from satellites or aircraft armed with sensors that detect electromagnetic wavelengths beyond the visible and infrared spectra (e.g., thermal) or sensors that transmit and detect their own energy (e.g., radar and LiDAR). Since the rest of the book addresses recent applications of remote sensing using the latter sensors, this chapter will briey discuss the early uses of remote sensing for mapping wetlands generally prior to the 1990s. Although current applications of remote sensing for wetland mapping in the United States were generally described in Chapter 3 when discussing the need for wetland mapping, an overview of historic uses of remote sensing for such purposes provides background for readers that are new to this topic before delving into more advanced applications of the technology. This chapter therefore presents an introduction to the uses of remote sensing for wetland detection prior to the 1990s and as such is intentionally brief with numerous references cited for further examination. Most early wetland mapping was conducted with aerial photos and less with satellite-derived imagery, hence the focus for this brief review.
