LiDAR Surveys Research Articles

Ancient lowland Maya complexity as revealed by airborne laser scanning of northern Guatemala.

Lowland Maya civilization flourished in the tropical region of the Yucatan peninsula and environs for more than 2500 years (~1000 BCE to 1500 CE). Known for its sophistication in writing, art, architecture, astronomy, and mathematics, Maya civilization still poses questions about the nature of its cities and surrounding populations because of its location in an inaccessible forest. In 2016, an aerial lidar survey across 2144 square kilometers of northern Guatemala mapped natural terrain and archaeological features over several distinct areas. We present results from these data, revealing interconnected urban settlement and landscapes with extensive infrastructural development. Studied through a joint international effort of interdisciplinary teams sharing protocols, this lidar survey compels a reevaluation of Maya demography, agriculture, and political economy and suggests future avenues of field research.

Lidar Uncovers Thousands of New Maya Structures

Jungle-piercing lidar surveys over ancient Maya sites give scientists the most extensive maps of lowland Maya civilization to date.

Spatial Discrimination of Complex, Low-Relief Quaternary Siliciclastic Strata Using Airborne Lidar and Near-Surface Geophysics: An Example from the Texas Coastal Plain, USA

Depositional units preserved on coastal plains worldwide control lithologic distribution in the shallow subsurface that is critical to infrastructure design and construction, and are also an important repository of information about the large-scale climate change that has occurred during many Quaternary glacial-interglacial cycles. The lateral and vertical lithologic and stratigraphic complexity of these depositional units and their response to climatic and sea-level change are poorly understood, making it difficult to predict lithologic distribution and to place historical and future climate and sea-level change within a natural geologic context. Mapping Quaternary siliciclastic depositional units on low-relief coastal plains traditionally has been based on their expression in aerial photographs and low-resolution topographic maps. Accuracy and detail have been hindered by low relief and lack of exposure. High-resolution airborne lidar surveys, along with surface and borehole geophysical measurements, are being used to identify subtle lateral and vertical boundaries of lithologic units on the Texas Coastal Plain within Quaternary strata. Ground and borehole conductivity measurements discriminate sandy barrier island and fluvial and deltaic channel deposits from muddy floodplain, delta-plain, and estuarine deposits. Borehole conductivity and natural gamma logs similarly distinguish distinct lithologic units in the subsurface and identify erosional unconformities that likely separate units deposited during different glacial-interglacial stages. High-resolution digital elevation models obtained from airborne lidar surveys reveal previously unrecognized topographic detail that aids identification of surface features such as sandy channels, clay-rich interchannel deposits, and accretionary features on Pleistocene barrier islands. An optimal approach to identify lithologic and stratigraphic distribution in low-relief coastal-plain environments employs ① an initial lidar survey to produce a detailed elevation model; ② selective surface sampling and geophysical measurements based on preliminary mapping derived from lidar data and aerial imagery; and ③ borehole sampling, logging, and analysis at key sites selected after lidar and surface measurements are complete.

Point bar sedimentation and erosion produced by an extreme flood in a sand and gravel-bed meandering river

In fluvial environments, extreme floods are often catalysts for substantial geomorphologic planform change. Despite the significant sediment erosion and deposition associated with high-magnitude, low-frequency floods, their sedimentological products often lack distinctive characteristics. However, the sedimentological expression of extreme floods in sand and gravel-bed meandering rivers has yet to be fully described. The sedimentological characteristics of a 1 in 100 year flood on a point bar of the South Saskatchewan River in Alberta, Canada, are investigated. Digital elevation models from multitemporal LiDAR surveys, field sediment sampling, measured sections, shallow boreholes, and aerial photographs were used to identify regions of sediment deposition and erosion, quantify the amount of vertical elevation change, and describe the sedimentology, stratigraphy and grain-size distribution of the flood deposit. The upstream portion of the point bar was dominated by high-velocity flow and erosion. The majority of sedimentation occurred at the meander-bend apex in lee and scroll bars composed of medium- to coarse-grained sand. Downstream of the bend apex, very fine- to fine-grained sand beds accumulated on ridges and lee bars. Silt, <10 cm thick, was deposited in the point bar interior. No single grain size or sedimentary structure typifies the flood deposit. Sedimentological evidence of extreme floods on point bars are likely best preserved in floodplain strata (rather than in-channel strata) and consist of beds with a coarser texture than what is normally dominant at that position on the point bar. In particular, the presence of gravel beds at high stratigraphic elevations appears indicative of an extreme-flood event. These criteria have been used to identify extreme-flood sediments in other coarse-grained point-bar deposits and may be applicable to the deposits of braided and wandering rivers, or lower-competence meandering rivers.

OUTCROP EXPLORER: A POINT-BASED SYSTEM FOR VISUALIZATION AND INTERPRETATION OF LiDAR DIGITAL MODELS

The use of LiDAR-based models for natural outcrops and surfaces studies has increased in the last few years. This technique has been found to be potential to represent digitally tridimensional data, thus it increases the quality and amount of data available for interpretation by geoscientists. Researchers, in computations, face difficulties in handling the huge amount of the data acquired by LiDAR systems. It is difficult to visualize efficiently the point cloud and convert it to high-quality digital models (DMs) with specific interpretation tools. Some in-house and commercial software solutions have been developed by some research groups and industries, respectively. However, all solutions must consider the large database as the pain point of the project. Outcrop Explorer has been developed to manage large point clouds, to provide interpretation tools, and to allow integration with other applications through data exporting. In terms of software architecture, view-dependent level of detail (LOD) and a hierarchical space-partitioning structure in the form of octree are integrated in order to optimize the data access and to promote a proper visualization and navigation in the DM. This paper presents a system developed for visualization, handling and interpretation of digital models obtained from point clouds of LiDAR surveys. This system was developed considering the free graphic resources, the necessities of the geoscientists and the limitations of the commercial tools for interpretation purposes. It provides an editing tool to remove noise or unnecessary portions of the point cloud and interpretation tools to identify lines and planes, as well as their orientations, and it has different exporting formats. However, being an open source project much more collaborative development is necessary.

3-D reconstruction of an abandoned montane reservoir using UAV photogrammetry, aerial LiDAR and field survey

The small reservoirs in the European montane landscape, which were built in past centuries for various purposes, represent specific cultural and technical heritage but also feature retention potential for mitigating the emerging impacts of climate change, namely, the course of flooding or droughts. However, the frequent lack of technical data on these historical structures, including their storage volume and flooded areas, prevents their consideration in water management planning.In this study, we used unmanned aerial vehicles (UAVs) to produce a detailed 3-D reconstruction of an abandoned montane reservoir that was built for timber flowing in the beginning of 19th century and that has not recently been used for any purpose. The UAV imaging and photogrammetric processing provided an ultra-high-resolution 3-D model of the reservoir basin (5 cm per pixel). Bathymetric analyses were performed based on this basin model to calculate the reservoir volume and flooded area for different water levels. The reliability of the UAV-based model was tested by comparing the results with those of elevation models derived from geodetic field survey using a total station and from conventional data sources based on available aerial LiDAR data. The data were compared to the historical estimates of the reservoir parameters found in the literature.Bathymetric reconstruction of the reservoir properties based on high-resolution UAV data revealed significant retention potential of the structure and historical underestimation of its capacity. The highly detailed UAV-based model helped to eliminate inaccuracies, resulting from the use of the generalized conventional elevation data, that affect the volumetric estimates in the flat topography of the reservoir basin. The study demonstrated the potential applicability of UAV technology for rapid and reliable reconstruction of landscape structures, which is significant for water management.

Underwater archaeology and submerged landscapes in western Australia

This research aims to explore the submerged landscapes of the Pilbara of western Australia, using predictive archaeological modelling, airborne LiDAR, marine acoustics, coring and diver survey. It includes excavation and geophysical investigation of a submerged shell midden in Denmark to establish guidelines for the underwater discovery of such sites elsewhere.

The influence of groundwater depth on coastal dune development at sand flats close to inlets

A cellular automata model is used to analyze the effects of groundwater levels and sediment supply on aeolian dune development occurring on sand flats close to inlets. The model considers, in a schematized and probabilistic way, aeolian transport processes, groundwater influence, vegetation development, and combined effects of waves and tides that can both erode and accrete the sand flat. Next to three idealized cases, a sand flat adjoining the barrier island of Texel, the Netherlands, was chosen as a case study. Elevation data from 18 annual LIDAR surveys was used to characterize sand flat and dune development. Additionally, a field survey was carried out to map the spatial variation in capillary fringe depth across the sand flat. Results show that for high groundwater situations, sediment supply became limited inducing formation of Coppice-like dunes, even though aeolian losses were regularly replenished by marine import during sand flat flooding. Long dune rows developed for high sediment supply scenarios which occurred for deep groundwater levels. Furthermore, a threshold depth appears to exist at which the groundwater level starts to affect dune development on the inlet sand flat. The threshold can vary spatially depending on external conditions such as topography. On sand flats close to inlets, groundwater is capable of introducing spatial variability in dune growth, which is consistent with dune development patterns found on the Texel sand flat.

Connectivity assessment in Mediterranean vineyards using improved stock unearthing method, LiDAR and soil erosion field surveys

AbstractThe interaction between processes and landforms is accelerated in vineyards due to bare tilled soils that enhance splash, runoff, and erosion. Traditionally, in order to assess these processes, the stock unearthing method (SUM) is considered a useful methodology that uses the graft union of the vine plant as passive bio‐indicator of the topsoil level changes. However, SUM assumes that the topography between the rows is planar when development of a model of the current micro‐topography is performed. Thus, we consider that there is a need to develop a new methodology (ISUM: improved SUM) that, by adding new measurements in the inter‐row areas (at least 3), allows inclusion of the absent micro‐topographical information of SUM. In this way, the main aim of this research was to estimate the micro‐topographical changes and soil transport at three different slope positions (upper, middle and lower parts) in a 25‐years‐old vineyard in eastern Spain. LiDAR data were used to compare the connectivity processes at the catchment with the pedon scale. We obtained maps that showed topsoil level changes and detected soil depletion and accumulation signals. We estimated soil displacement rates of –1.6 Mg ha yr‐1 (depletion), +2.8 Mg ha yr‐1 and +13.3 Mg ha yr‐1 (accumulation) at upper, middle and lower slope positions, respectively. The total average soil erosion rates in the inter‐rows were –5.7 Mg ha‐1 yr‐1. In the row areas, deposition of +10.5 Mg ha yr‐1 was measured. Field erosion marks surveyed after each rainfall event gave insights to the connectivity at the inter‐row and the slope scale. It was found that at the row scale there were sinks of sediments underneath the vines and sources in the inter‐row parts, although they are the highest and lowest local topographical terrain, respectively. This is due to tillage erosion that redistributed the sediments. At the slope scale, the lower part of the slope collected sediments from the upper slope positions, which were transported along the middle part of the slope, as the measurement of ISUM and the field survey after intense rainfall events demonstrated. Connectivity of the flows along the whole slope were rare (twice), and along individual slope parts connectivity was found eight times, and 19 at the inter‐row scale after 8 years of field observations. Copyright © 2018 John Wiley &amp; Sons, Ltd.

Automatically Generated Vegetation Density Maps with LiDAR Survey for Orienteering Purpose

Abstract. The focus of our research was to automatically generate the most adequate vegetation density maps for orienteering purpose. Application Karttapullatuin was used for automated generation of vegetation density maps, which requires LiDAR data to process an automatically generated map. A part of the orienteering map in the area of Kazlje-Tomaj was used to compare the graphical display of vegetation density. With different settings of parameters in the Karttapullautin application we changed the way how vegetation density of automatically generated map was presented, and tried to match it as much as possible with the orienteering map of Kazlje-Tomaj. Comparing more created maps of vegetation density the most suitable parameter settings to automatically generate maps on other areas were proposed, too.

Recent Trends and Long-standing Problems in Archaeological Remote Sensing

The variety and sophistication of data sources, sensors, and platforms employed in archaeological remote sensing have increased significantly over the past decade. Projects incorporating data from UAV surveys, regional and research-driven lidar surveys, the uptake of hyperspectral imaging, the launch of high-temporal revisit satellites, the advent of multi-sensor rigs for geophysical survey, and increased use of structure from motion mean that more archaeologists are engaging with remote sensing than ever. These technological advances continue to drive research in the specialist community and provide reasons for optimism about future applications, but many social and technical obstacles to the integration of remote sensing into archaeological research and heritage management remain. This article addresses the challenges of contemporary archaeological remote sensing by briefly reviewing trends and then focusing on providing a critical overview of the main structural problems. The discussion here concentrates on topics that have dominated the discourse in recent archaeological literature and featured prominently in ongoing fieldwork for the past decade across three broad segments of landscape archaeology: data collection in the field, the current state of data access and archives, and processing and interpretation.

Bar Migrations on a Macrotidal Ebb Delta over a Period of Six Years Using Lidar Survey

Pellerin Le Bas, X. and Levoy, F., 2018. Bar migrations on a macrotidal ebb delta over a period of six years using LiDAR survey. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 146–150. Coconut Creek (Florida), ISSN 0749-0208.The migration rates of two swash bars on an ebb delta are studied in a macrotidal environment. A dataset of 12 LiDAR surveys, from 2011 to 2017 is used to compute the movement of the swash bar crests using Digital Shoreline Analysis System (DSAS) version 4.3. Hydrodynamic data are acquired near the ebb-tidal delta during the same period. The relationship between bar migration rate and wave energy flux is analyzed. The correlation is high (r2 = 0.71), but a specific migration rate of the two bars weaken this result. Furthermore, the two swash bars have two different behaviors under the same hydrodynamic conditions. Other analyses are conducted concerning the relationships between the migration of the bar and its volume or the water depth. The correlations are too weak to explain the different behaviors of the bars. Another parameter is highlighted, the number of swash bars in the immediate vicinity of the two bars.

Cliff Retreat Induced by Series of Storms at Międzyzdroje (Poland)

ABSTRACT Terefenko, P.; Giza, A.; Paprotny, D.; Kubicki, A., and Winowski, M., 2018. Cliff Retreat Induced by Series of Storms at Miedzyzdroje (Poland). In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 181–185. Coconut Creek (Florida), ISSN 0749-0208. In Miedzyzdroje, a coastal town in Poland, significant cliff retreat has been observed in recent times. It used to be considered mainly a response to storm events with particularly high water levels and wave energy. However, morphology of cliff coasts is shaped not only by the most extreme storm surges or by a number of accompanying processes such as precipitation. Much wider effects are now being linked to the occurrence of series of subsequent storms. This research uses a set of five terrestrial LiDAR surveys carried out between November 2016 and April 2017 to determine short-term cliff erosion associated with t...

Effect of Tree Phenology on LiDAR Measurement of Mediterranean Forest Structure

Retrieval of forest biophysical properties using airborne LiDAR is known to differ between leaf-on and leaf-off states of deciduous trees, but much less is understood about the within-season effects of leafing phenology. Here, we compare two LiDAR surveys separated by just six weeks in spring, in order to assess whether LiDAR variables were influenced by canopy changes in Mediterranean mixed-oak woodlands at this time of year. Maximum and, to a slightly lesser extent, mean heights were consistently measured, whether for the evergreen cork oak (Quercus suber) or semi-deciduous Algerian oak (Q. canariensis) woodlands. Estimates of the standard deviation and skewness of height differed more strongly, especially for Algerian oaks which experienced considerable leaf expansion in the time period covered. Our demonstration of which variables are more or less affected by spring-time leafing phenology has important implications for analyses of both canopy and sub-canopy vegetation layers from LiDAR surveys.

A Generalized Lidar-Based Model for Predicting the Merchantable Volume of Balsam Fir of Sites Located along a Bioclimatic Gradient in Quebec, Canada

Lidar-based models rely on an optimal relationship between the field and the lidar data for accurate predictions of forest attributes. This relationship may be altered by the variability in the stand growth conditions or by the temporal discrepancy between the field inventory and the lidar survey. In this study, we used lidar data to predict the timber merchantable volume (MV) of five sites located along a bioclimatic gradient of temperature and elevation. The temporal discrepancies were up to three years. We adjusted a random canopy height coefficient (accounting for the variability amongst sites), and a growth function (accounting for the growth during the temporal discrepancy), to the predictive model. The MV could be predicted with a pseudo-R2 of 0.86 and a residual standard deviation of 24.3 m3 ha−1. The average biases between the field-measured and the predicted MVs were small. The variability of MV predictions was related to the bioclimatic gradient. Fixed-effect models that included a bioclimatic variable provided similar prediction accuracies. This study suggests that the variability amongst sites, the occurrence of a bioclimatic gradient and temporal discrepancies are essential in building a generalized lidar-based model for timber volume.

LANDSLIDE MONITORING AND ASSESSMENT FOR HIGHWAY RETAININGWALL: THE CASE STUDY OF TAŞKENT(TURKEY) LANDSLIDE

Abstract. Landslide monitoring and assessment of the highways retaining walls are a crucial task. Because there exist a risk and danger with regard to the movement of the wall to the highway by landslide force that may spread further. To evaluate the changing, movements have to be monitored. For this reason, we practised mobile LiDAR surveys on the landslide effected wall on the highway. The usage of the mobile LiDAR systems have significantly increased in recent years, especially for road management. Currently, mobile LiDAR technology is capable of measuring the earth surface with high precision and density as a 3D point clouds. As stated in this study, the point cloud data processing have been analysed further and the wall surface points fitted to a plane object for monitoring of the landslide effects. This study focuses on different plane fitting algorithms which represents the retaining wall, a performance assessment and evaluation of the deformation between two plane models. The analysis indicates that the uncertainty of the measurements between the two epochs on stable areas survey was within ±2 cm. According to the experimental results, the proposed methods performed promising results that can be used for monitoring of retaining walls for fast processing and assessment.

Probabilistic liquefaction-induced lateral spread hazard mapping and its application to Utah County, Utah

Earthquake-induced liquefaction may result in the lateral spread displacement of soil down gently sloping ground or towards a free-face, causing severe and costly damage to various facilities, bridges, buildings and other critical infrastructure. Despite the availability of analytical methods, most engineers currently use empirical or semi-empirical regression models to estimate liquefaction-induced lateral spread displacements at specific sites. However, the application of these regression models for regional mapping over a large geographic areas can be difficult because of challenges associated with the adequate characterization of subsurface soil and groundwater conditions, geotechnical properties, regional topography, and uncertainties associated with the causative seismic loading. To address these challenges, this paper presents a new and fully probabilistic procedure for regional hazard mapping of liquefaction-induced lateral spread displacement. The mapping process is demonstrated through an implementation in Utah County, Utah. To demonstrate the type of lateral spread displacement hazard maps possible, maps corresponding to return periods of 1033 and 2475years are developed for Utah County, Utah. The proposed procedure incorporates topographical data from airborne lidar surveys and geotechnical and geological data from available maps and subsurface explorations. It accounts for uncertainties in the soil properties, seismic loading, and the empirical models for predicting lateral spread displacement using Monte Carlo simulations.

A mathematical framework to describe the effect of beam incidence angle on metrics derived from airborne LiDAR: The case of forest canopies approaching turbid medium behaviour

Airborne laser scanning (LiDAR) is used in forest inventories to quantify stand structure with three-dimensional point clouds. However, the 3D distribution of the point clouds depends not only on stand structure, but also on scan angle, because the probability for an oblique beam to be reflected by the canopy increases with the distance it must travel through the canopy. Thus, the canopy appears to increase in density as the incidence angle increases, all else being equal. The resulting variation between and within datasets can induce bias in LiDAR metrics derived from the vertical distribution of points. In this study, we modelled the effect of scan angle on the vertical structure of the point clouds to predict the bias of metrics derived from points sampled off-nadir. Comparison with paired observations from different flightlines (off- and at-nadir observations of the same point) demonstrated that the model accurately reproduced the bias of metrics calculated for a northern hardwood forest with relatively continuous canopy. Thus, the model could be used to correct the bias of LiDAR metrics, and provides a mathematical framework that could be used to inform the selection of maximum incidence angle in LiDAR surveys, considering the trade-off between decreasing acquisition costs and obtaining unbiased measurements.

Geomorphic impact and assessment of flexible barriers using multi-temporal LiDAR data: The Portainé mountain catchment (Pyrenees)

Multi-temporal digital elevation models (DEMs) obtained from airborne LiDAR surveys are widely used to detect geomorphic changes in time and quantify sediment budgets. However, they have been rarely applied to study the geomorphic impact of engineering structures in mountain settings. In this study, we assessed the influence and behavior of flexible sediment retention barriers in the Portainé catchment (Spanish Pyrenees), using three LiDAR data sets (2009, 2011 and 2016) that covered a 7-year period. Densely forested mountainous areas present some limitations for reliable DEM analysis due to spatial variabilities in data precision, accuracy and point density. A new methodological approach for robust uncertainty analysis along channels, based on changes in cross-sectional elevations, was used to discriminate noise from real geomorphic changes. The obtained results indicated that erosion occurs along most reaches covering a large area, whereas deposition is localized in specific areas such as those upstream of sediment retention barriers and in the debris cone. Despite the presence of 15 flexible sediment retention barriers, the channels presented net degradation during both 2009–2011 and 2011–2016, with 2838 and 147 m3 of material exported from the basin, respectively. For the same periods, the barriers retained 33% and 25% of the total deposition (up to 1300 m3 per barrier), respectively, but also induced lateral and downstream incision, the latter reaching 703 m3 for a single barrier. We detected a horizontal displacement of the net of up to 1.2 m in filled barriers, resulting from net flexion. The interference of the natural river evolution by defense measures has resulted in a complex erosion-deposition pattern. The presented methods show high potential for the hydrogeomorphic study of mountain catchments, especially for a high-resolution assessment of flexible barriers or other engineering structures in remote areas.

Damage Assessment by Laser Could Focus Postearthquake Response

Airborne lidar surveys taken before and after a powerful 2016 earthquake in Japan revealed the potential for such surveys to identify hard-hit buildings quickly.