This article gives an overview of the various aspects of ground-penetrating radaras used in archaeology. Aftera short overview ofthe historicaldevelopment ofthe technique, the most important physical parameters and principles are explained. This includes relative dielectric constant, conductivity, attenuation, horizontal and vertical resolution, wavelength and footprint.The focus is on data processing and some ofthe pitfallsinvolved.Severalalgorithmsfrom seismic data processing are described, including migration. Stress is laid on the generation of time-or depth-slices as the basis for displaying the data. Using three-dimensional visualization techniques can enhance this, but interpretation in combination with other data, preferably within a geographical information system, remains the important last step.The advantages of modelling are explained and presented with the range of possible applications. Many the techniques and methods described are subsequently used in four case histories, ranging from a survey on a lake to a three-dimensional model of a part of a roman town.Finally some thoughts about the future development of the method are presented.

Excavations around the Prediger Church in Zurich (Switzerland) for a building project prompted interest in the region beneath the choir, which dates from the thirteenth century. To supplement archaeological information on the church, the hidden remains beneath the choir were investigated with ground-penetrating radar (GPR). An initial coarse GPR survey with shielded highfrequency antennae mapped the locations and dimensions of buried walls beneath the choir. The choir was determined to be rectangular and an altar was discovered. The rectangular ground plan of the historic choir is typical for a Cistercian church. To resolve the exact dimensions of structures, migration of the data was required. The most important parameter for this process is the velocity model of the ground, which was determined by different methods: constant velocity migration tests of the GPR data, common mid-point analyses, time-domain reflectometry in drill holes and network analyser measurements on samples. A second GPR survey with a very fine grid was carried out over a small area to test the resolution capabilities of this method. A threedimensional display of semi-automatic selected interfaces allowed the identification of single rocks. Such detail provided an insight into the construction and the state of destruction or preservation of the walls.

Among the different geophysical prospecting methods applied in archaeology, ground‐penetrating radar is one that still requires a lot of time to carry out field recordings. A duo‐antenna configuration is proposed that will halve the time needed in the field. Tests have shown that this can be done without any interference between the two antennae. The signals from different antennae do not have the same characteristics and the spectrum and amplitude of the traces are not the same. The use of spectral whitening and energy matching for adjacent traces or samples makes the data sets as similar as possible to allow for unperturbed time‐ or depth‐slices. As a side effect, spectral whitening enhances the vertical resolution and penetration depth of the method.