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he investigated, Reisner also developed formal typologies of pottery and other artifacts. Finally, his introduction of the use of standard grave-recording forms has already been mentioned. He was fond of saying that a well-conducted excavation should be recorded in such a way that future scholars could reconstruct every detail of the conditions found by the original diggers. His British colleague, Herbert Winlock, asserted that Reisner was the greatest excavator of Egyptian antiquities then alive, while walter b. emery went so far as to assert that he was the greatest archaeologist America had ever produced.

Although from 1910 onward Reisner held appointments both as professor of Egyptology at Harvard and as curator of Egyptian Art at the Boston Museum, he was quintessentially a field man. He spent nearly the whole of every year in the Nile Valley, digging in Egypt in the summer and in the Sudan in the winter, and returned only intermittently to give courses at Harvard and to attend to his curatorial duties at the museum. His later years were plagued by poor health and failing eyesight, which eventually forced him to give up his university appointment, but he remained active as director of the Harvard-Boston excavations until the end of his life. He died in his field camp on the Giza Plateau on 6 June 1942.

Because of his almost single-minded dedication to fieldwork, Reisner published final reports on only a few of his excavations. After his death, final reports on most of his Sudan excavations were published by his longtime assistant and colleague, Dows Dunham, and William Kelly Simpson published individual reports on many of the Giza tombs.

William Y. Adams

Remote Sensing

Remote sensing has been defined as the science and art of obtaining information about an object, area, or phenomenon through the analysis of data procured by indirect means. In other words, information is obtained by the use of a device that is not in direct contact with the subject under investigation. In the broadest sense, different techniques can be considered as remote sensing. These range from subsurface sensing methods, such as ground-penetrating radar, seismometer, and soil resistivity, to the analysis and interpretation of the electromagnetic energy radiated from the surface of the earth, recorded on air- and spaceborne platforms in the form of aerial photography, and satellite and radar imagery. This article deals only with the latter forms.

Basic Principles of Electromagnetic Energy

In simple terms, electromagnetic energy is the energy that is emitted or reflected from all objects. The emission of this energy is picked up by special airborne or spaceborne sensors and is processed in photographic or digital form. In reality, only the sun emits strong enough electromagnetic energy to be picked up by the sensors; the remaining objects on the earth’s surface will reflect the energy they receive from the sun. Visible light is the most common form of electromagnetic energy, but other familiar forms of electromagnetic energy are heat, ultraviolet rays, radio waves, microwaves, and X-rays.

Electromagnetic energy radiates in waves that travel in harmonic sinusoidal movements. The length of the waves varies, and in the process gives place to a range of wavelength variation known as the electromagnetic spectrum. The part of this spectrum that we are more familiar with is the optical wavelength, which is divided into several bands for remote sensing purposes. The visible light that can be perceived by the human eye forms a fraction of the optical wavelengths. It comprises the blue, green, and red bands with a wavelength range that goes from about 0.4 to 0.5 μm, 0.5 to 0.6 μm, and 0.6 to 0.7 μm, respectively. Outside the visible range adjoining the blue band is the ultraviolet band (UV), which has a wavelength