Aerial and geophysical methods are widely used and valuable techniques for the detection, mapping and curation of the fragile archaeological resource.  However, the changing geophysical properties of the soil, which vary spatially, seasonally and throughout the day, and their effect on sensor responses are poorly understood.  A long term monitoring strategy to record the changing conductivity, permittivity and temperature, and the differences in these factors between an archaeological ditch feature and the surrounding soil matrix at different depths was thought to be of some benefit for informing future use of these technologies.  The use of geotechnical properties, such as moisture content, density and particle size distribution, along with local weather data collected on site can be linked and used as a proxy for the geophysical response and feature contrast, through the use of dielectric mixing models.

This paper aims to present a novel method for examining these contrast factors using Time Domain Reflectometry (TDR), a long standing electromagnetic technique used to monitor soil moisture in environmental, engineering and soil science research.  The design and development of a monitoring station, suitable for a long term data collection strategy, and the methodology for field installation will be discussed.  Particular attention will be given to the challenges faced, and the methods used to solve them.  The large raw waveform datasets collected by the stations also present a challenge for interpretation, requiring processing to produce geophysical properties.  Attention will also be given to the mathematical methods for interpreting these raw waveforms and the development of an automated script in MATLAB, capable of converting the waveforms to permittivity and conductivity values.  Finally, some preliminary data from the monitoring stations will be presented to highlight the type of information the project is producing, and its significance is briefly discussed.

This research forms part of the DART project (Detection of Archaeological residues using Remote sensing Techniques), a three year, multi-university and multi-disciplinary project.  It aims to enhance knowledge of the science behind the detection of archaeological features using aerial and geophysical methods, particularly on soils which are traditionally unresponsive, such as those with high clay content.