Processing stepped frequency continuous wave GPR systems to obtain maximum value from archaeological data sets

ABSTRACT Stepped frequency continuous wave ground penetrating radar (GPR) systems allow highly detailed data sets to be collected across a wide bandwidth using a multi‐element array antenna, such as the 3D‐radar GeoScope system. Although the final presentation of the results is similar to time‐domain systems, the correct processing of the initial frequency domain data acquired in the field is essential to obtain the maximum information from the site. Processing begins with the identification of a suitable frequency window for conversion to the time‐domain using an inverse Fourier transform and demonstrates how the use of a varying frequency window with depth can improve the final results. Various methods for background subtraction to minimize the loss of data quality and cope with the strong surface reflection experienced by an air‐launched antenna are also explored. The geometry of the air‐launched antenna is also considered with specific regard to developing a three‐dimensional migration model that accounts for the variation in a signal response expected from such a system. This paper explores these themes with relation to data from archaeological sites and also considers the data processing challenges presented by high density (e.g., 0.075 m x 0.075 m) multi‐hectare surveys.