Survey Techniques

This year’s introductions to techniques include:

  • field survey & metal detection
  • magnetics
  • ground-penetrating radar (GPR)
  • drone photogrammetry
  • structure from motion (SfM)
  • Visualizing and interpreting LiDAR imagery of the surrounding landscape

Field survey / Metal detection

A metal detector is a survey method to provide quick information of potential cultural activity. The wire coil transmits an electro-magnetic field into the soil. This induces a secondary electromagnetic field in a small conductive mass (ferrous metal objects, e.g. scrap iron, but also nonferrous metals), which the instrument can measure.


The smallest disturbances of the earth's magnetic field can be detected by magnetometers. The applied probes measure these variations, e.g. be caused by scrap iron, material burned under great heat, or by magnetotactic bacteria in order to create a 2-dimensional map of the magnetic disturbances, to  draw conclusions about the cultural use of a landscape.

Groundpenetrating Radar (GPR)

GPR is probably the most versatile geophysical instrument applied in archaeological prospection. In the process, transmitted electromagnetic waves are reflected by layer boundaries which, as a sum, provide a profile of the background. This enables a 3-dimensional mapping of foundations and other archaeological traces, as well as a detailed structural analysis of buildings.

Structure from Motion/ drone photogrammetry

Structure from Motion (SfM) uses the principle that movement through a scene allows an understanding of the shape of the scene in three dimensions. Images can be captured from the ground or by using drones or UAVs (Unmanned Aerial Vehicles). SfM requires at least 3 images of each part of the object. Specialised software automatically selects distinctive points in the photographs, and thousands of these points are matched together. The result is a detailed metric and coloured dataset that is similar to the 3D point clouds produced by laser scanning.

LiDAR (Light Detection and Ranging)

In order to analyze the collected data sets in terms of the castles cultural history and geographic environment, LiDAR (Light Detection and Ranging) data will serve to generate and visualize a digital terrain model, to compare and interpret it with visible structures in the field.