Lidar Investigation of Knockdhu Promontory and its Environs, County Antrim, Northern Ireland

Abstract

A high-resolution aerial lidar survey (up to 40 points m -2 ) has been carried out in the environs of Knockdhu Promontory in the Antrim Uplands, which is recognized as one of Northern Ireland's most important relict multiperiod archaeological landscapes. This lidar survey was amongst the first such surveys commissioned specifically for archaeological purposes in Northern Ireland and has helped to re-evaluate the archaeological landscape character of a 9 km 2 study area and inform future conservation studies. Sampled ground observation was undertaken in an attempt to provide a higher degree of interpretive integrity. These field observation exercises also highlighted the importance of the high vertical resolution of the data (0.05 m at 2σ (95% confidence level)) in delineating extremely subtle upstanding earthwork features that had hitherto gone unnoticed. Much of the archaeological evidence identified can be broadly ascribed to the early post-medieval period (AD 1599-1750); this includes field boundaries, cultivation furrows, enclosures, transhumance huts, abandoned settlements and associated pathways, but the higher ground of the Antrim Plateau in this locality is also characterized by evidence of prehistoric activities and substantial earthworks survive such as the 'Linford Barrows' and 'Knockdhu Promontory Fort'. The lidar study has identified as many as 285 previously unrecorded potential archaeological sites and amended existing records within the Northern Ireland Sites and Monuments Record (NISMR) and has proved transformational as a technique to 'open up' the Ulster uplands for archaeological study.

Origin and Holocene geomorphological evolution of the landslide-dammed basin of la Narse de la Sauvetat (Massif Central, France)

“…Classified bare earth points were then interpolated using the natural neighbor method and converted into a raster DTM with a resolution of 0.5 m, considered optimal for geomorphological analysis (Lin et al, 2013;Mcneary, 2014;Tarolli, 2014). The slope raster and the Local Relief Model (Hesse, 2010) were calculated in a selected area of the resulting DTM (topographic threshold, see Fig.…”

The Highest Gradient Model: A New Method for Analytical Assessment of the Efficiency of LiDAR-Derived Visualization Techniques for Landform Detection and Mapping

“…Additionally, it is not dependent upon the illumination direction (unlike shading models) and interpretation is straightforward [35]. Local Relief Model or LRM [31] is an upgrade of the classical trend removal technique, considered especially useful for light relief in flat areas [30,34,35]. Both VTs are usually classified as DEM-manipulating methods.…”

“…A 0.50 m pixel size is considered to be sufficient to preserve all the detail of bare earth point clouds and so to detect geomorphological and archaeological features [2,30,41]. The resulting raster DTM of LiDAR data were acquired by airborne laser scanner in March 2014 with a minimum of 18 emitted laser pulses per square meter.…”

Automatic detection of complex archaeological grazing structures using airborne laser scanning data

“…In this study, MDOW, LRM, SKV and openness were calculated using the RVT software (Relief Visualization Toolbox, 2015;Zakšek et al, 2014;Zakšek et al, 2011;Kokalj et al, 2011). We chose LRM as the best candidate to test the success of the automatic detection algorithm because it's well suited in the case of slight relief and because it causes a negligible horizontal shift in the position of features (Bennett et al, 2012;Mcneary, 2014), which is important for the automatic localisation of the archaeological structures. The principle of the LRM computation is to apply a high pass filter to the DTM, so that only the highest frequencies component of dataset, corresponding to high altitude gradient dx dz or dy dz , which may be associated to anthropogenic landforms, are conserved.…”