f Radar analysis applied to cultural heritage in northern Spain

The geo-radar (Ground Penetrating Radar, GPR) is a good prospective non-destructive tool for depths varying between some centimeters and a few meters. The GPR is a compact and portable system, with a great variety of antennas and a high resolution power, which make it very useful either in detecting and locating ground anomalies and surface structures or in detecting construction problems. Prospecting technique with GPR has improved fast in recent years due to a rising demand both in quantity and required quality. Important advantages of GPR systems are, among others, that antennas must not be necessarily contacting ground surface when working, and that they can be designed, at least theoretically, to work at a desired central frequency with appropriated band widths. Nevertheless good results will be only obtained when taking in consideration ground nature and geometry. The first studies involving electromagnetic waves are from the beginning of this century. Several works were made to find metal objects buried beneath ground’s surface, and some others trying to locate buried objects. Important work was done, during 1923 to 1928, by the Institute of Applied Geophysics of Moscow, studying the penetration of radio waves in salty soils. In the second half of this century, during the 50’s and the 60’s, Wait (1960,1962) proposed his theory of electromagnetic wave propagation. Three decades were needed to introduce the technique in Civil Engineering due, basically, to the necessity of a scale change. In this way, the usage of mono-impulses began and so did the design of georadars, appearing the Ground Penetrating Radar (GPR). In the last 25 years there has been a constant improvement of GPR. Its commercialization began in the 70’s and the First International Congress of GPR Applications was held in the U.S.A. in 1986. There have also appeared a lot of publications about GPR and its applicability has spread throughout geology, minery and civil engineering, and geotechnical and archaeological investigations as well (Ulriksen, 1982; Lorenzo, 1994; Canas et al. 1996; García, 1997).