Remote Sensing

Lidar, Radar and Geophysics

Services

AMS offers a range of remote sensing services that utilise the most advanced technologies and state-of-the-art equipment to locate and map subsurface archaeological remains. Typically deployed at pre-planning and design stage, remote sensing helps our clients to minimise archaeological risk to project schedules and enhance confidence in the successful delivery of development projects.

Operating across Ireland and the UK, our dedicated survey team provides magnetometry, earth resistance, electromagnetic induction, ground penetrating radar and metal detection surveys, as well as Lidar capture and analysis.

LiDAR

Lidar (Light Detection and Ranging) is a remote sensing technique used to generate high-resolution 3D models of the ground surface which can help archaeologists identify and record various aspects of the historic environment.

The processed data can be manipulated by a range of techniques and software that can aid in the discovery of low-profile archaeological features, including those hidden beneath woodland canopy.

Some of the main visualisation techniques for Lidar data include:

Analytical hill-shading: artificial illumination is used to highlight surface changes such as upstanding features (mounds, walls etc.) and sunken features (ditches etc.). Greater illumination can be achieved by calculating analytical hill-shading in multiple directions equally distributed between 0° and 360°.
Principal Components Analysis: a mathematical model that ‘summarises’ the information of hill-shade models from different directions.
Sky-view factor: measures the portion of the sky visible above a certain point. In this way, flat terrain, ridges and earthworks which receive more illumination are highlighted and appear in light, while depressions appear dark because they receive less illumination.
Slope gradient: represents the maximum rate of change between each data cell and its neighbours and can be calculated either as degree of slope or as percentage of slope. This technique works especially well in combination with hill-shading and also works well on most types of terrain.
Openness: is a proxy for diffuse illumination. Positive Openness is similar to sky-view factor but with a more ‘flattened feel’, while Negative Openness provides additional information on convex features.

Geophysics

Our surveyors have a wealth of geophysical expertise and can advise on the most appropriate geophysical methods and survey strategies to meet the requirements of any project.

Central to our approach is the implementation of high-resolution survey instruments that are capable of mapping extensive areas in the most rapid and cost-effective manner. Data are collected using both hand-pushed and ATV-pulled systems that combine geophysical survey technology with centimetre-precision GPS. This strategy produces a highly detailed dataset that gives the utmost clarity to any archaeological features detected. The survey results can complement and inform other investigative techniques such as test excavation to fully evaluate the archaeological potential of any site.

Drone Imaging

UAV/UAS Drone Imaging

Unmanned aerial vehicles or systems (UAV/UAS) are commonly referred to as drones. These are used to record conventional aerial photographs and video footage of each specified place, building or monument and its landscape setting. Images captured include vertical overhead and oblique views from different aspects (north, south, east and west) and at different elevations.

AMS employs two qualified drone pilots:

Liamóg Roche
Dr James Bonsall

Both have completed the Irish Aviation Authority and European Union Aviation Safety Agency mandated training. Both also hold a Remote Pilot Certificate of Competency.

Electromagnetic Induction (EMI)

EMI simultaneously measures the quadrature (conductivity) and in-phase (magnetic susceptibility) components of a soil volume, allowing for the detection of infilled features such as ditches and pits, as well as structural remains such as buried foundations. This technique can detect archaeological features to a depth of 3.2m.

Earth Resistance

This technique measures variations in the moisture content of the soil and can identify and map buried stone features (such as walls and roadways) and silted-up ditches.

Ground-Penetrating Radar (GPR)

GPR is generally used for the detection of building foundations and burial remains and records the two-way travel time of electromagnetic energy transmitted from the surface through the underlying soil.

Metal Detection

Deployed as part of initial site assessments, metal detection is an effective method of investigation used to identify and map metallic objects in the topsoil, including archaeological artefacts. Our experienced detectorists use advanced equipment and operate under special licences from the Irish Government in line with legal requirements.