Michael J. Olsen

Terrestrial Laser Scanning-Based Structural Damage Assessment

Terrestrial laser scanning (TLS) provides a rapid, remote sensing technique to model 3D objects. Previous work applying TLS to structural analysis has demonstrated its effectiveness in capturing simple beam deflections and modeling existing structures. This paper extends TLS to the application of damage detection and volumetric change analysis for a full-scale structural test specimen. Importantly, it provides a framework necessary for such applications, in combination with an analysis approach that does not require tedious development of complex surfaces. Intuitive slicing analysis methods are presented, which can be automated for rapid generation of results. In comparison with conventional photographic and surface analysis methods, the proposed approach proved consistent. Furthermore, the TLS data provided additional insight into geometric change not apparent using conventional methods. As with any digital record, a key benefit to the proposed approach is the resulting virtual test specimen, which is available for posttest analysis long after the original specimen is demolished. Uncertainties that can be introduced from large TLS data sets, mixed pixels and parallax in the TLS analysis are also discussed.

Synthesis of Transportation Applications of Mobile LIDAR

A thorough review of available literature was conducted to inform of advancements in mobile LIDAR technology, techniques, and current and emerging applications in transportation. The literature review touches briefly on the basics of LIDAR technology followed by a more in depth description of current mobile LIDAR trends, including system components and software. An overview of existing quality control procedures used to verify the accuracy of the collected data is presented. A collection of case studies provides a clear description of the advantages of mobile LIDAR, including an increase in safety and efficiency. The final sections of the review identify current challenges the industry is facing, the guidelines that currently exist, and what else is needed to streamline the adoption of mobile LIDAR by transportation agencies. Unfortunately, many of these guidelines do not cover the specific challenges and concerns of mobile LIDAR use as many have been developed for airborne LIDAR acquisition and processing. From this review, there is a lot of discussion on “what” is being done in practice, but not a lot on “how” and “how well” it is being done. A willingness to share information going forward will be important for the successful use of mobile LIDAR.

A Review of LIDAR Radiometric Processing: From Ad Hoc Intensity Correction to Rigorous Radiometric Calibration

In addition to precise 3D coordinates, most light detection and ranging (LIDAR) systems also record “intensity”, loosely defined as the strength of the backscattered echo for each measured point. To date, LIDAR intensity data have proven beneficial in a wide range of applications because they are related to surface parameters, such as reflectance. While numerous procedures have been introduced in the scientific literature, and even commercial software, to enhance the utility of intensity data through a variety of “normalization”, “correction”, or “calibration” techniques, the current situation is complicated by a lack of standardization, as well as confusing, inconsistent use of terminology. In this paper, we first provide an overview of basic principles of LIDAR intensity measurements and applications utilizing intensity information from terrestrial, airborne topographic, and airborne bathymetric LIDAR. Next, we review effective parameters on intensity measurements, basic theory, and current intensity processing methods. We define terminology adopted from the most commonly-used conventions based on a review of current literature. Finally, we identify topics in need of further research. Ultimately, the presented information helps lay the foundation for future standards and specifications for LIDAR radiometric calibration.

Comparison of airborne and terrestrial lidar estimates of seacliff erosion in Southern California.

Seacliff changes evaluated using both terrestrial and airborne lidar are compared along a 400 m length of coast in Del Mar, California. The many large slides occurring during the rainy, six-month study period (September 2004 to April 2005) were captured by both systems, and the alongshore variation of cliff face volume changes estimated with the airborne and terrestrial systems are strongly correlated (r 2 = 0.95). How- ever, relatively small changes in the cliff face are reliably detected only with the more accurate terrestrial lidar, and the total eroded volume estimated with the terrestrial system was 30 percent larger than the corresponding airborne estimate. Although relatively small cliff changes are not detected, the airborne system can rapidly survey long cliff lengths and provides coverage on the cliff top and beach at the cliff base.

New Automated Point-Cloud Alignment for Ground-Based Light Detection and Ranging Data of Long Coastal Sections

This paper presents new techniques with corresponding algorithms to automate three-dimensional point-cloud georeferencing for large-scale data sets collected in dynamic environments where typical controls cannot be efficiently employed. Beam distortion occurs at the scan window edges of long-range scans on near-linear surfaces from oblique laser reflections. Coregistration of adjacent scans relies on these overlapping edges, so alignment errors quickly propagate through the data set unless constraints (origin and leveling information) are incorporated throughout the alignment process. This new methodology implements these constraints with a multineighbor least-squares approach to simultaneously improve alignment accuracy between adjacent scans in a survey and between time-series surveys, which need to be aligned separately for quantitative change analysis. A 1.4-km test survey was aligned without the aforementioned constraints using global alignment techniques, and the modified scan origins showed poor ag...

Tohoku Tsunami-Induced Building Failure Analysis with Implications for U.S. Tsunami and Seismic Design Codes

The structural details of numerous damaged buildings in the Tohoku region were documented soon after the 11 March 2011 Tohoku-oki earthquake and tsunami by a reconnaissance team sponsored by the American Society of Civil Engineers. Tsunami flow depths and velocities were determined based on analysis of video records and the observed effects on simple benchmark structures in the flow. Equations for various conditions of fluid loading were then validated through failure analyses completed for several buildings, using finite element modeling and LiDAR scans. These analysis tools were applied full-scale to buildings with clearly identified failure mechanisms to validate methodologies to be included in a new chapter on “Tsunami Loads and Effects” in the ASCE 7-2016 Standard, Minimum Design Loads for Buildings and Other Structures. These findings, together with an analysis of the inherent seismic inelastic capacities of mid-rise buildings, are relevant for establishing the loadings and performance objectives proposed for the new chapter on “Tsunami Loads and Effects” in the ASCE 7 Standard.

Optical techniques for multiscale damage assessment

Remotely sensed optical images coupled with advanced analysis techniques provide critical information for pre-disaster hazard and post-disaster damage assessment. Utilizing optical techniques, such as Light Detection and Ranging (LIDAR) and satellite imagery, this paper presents several geohazard studies with a broad range of scales, from regional to local component. In this analysis, a common workflow emerges, namely: (i) site survey, (ii) data acquisition, (iii) post-processing and (iv) analysis and interpretation. The end result will depend largely on the scale and type of hazards, degree and extent of damage, and acquisition method. Results from several case studies are presented that reflect this diverse dependency. These case studies include damaged structures from the Indonesia and American Samoa tsunamis, San Diego coastal erosion, and cracking of a historical building in Italy. The results show that recently developed change detection algorithms can quickly provide regional damage information if optical imagery is available. The development of a rich database of baseline information is critical for geohazard analysis. Frequent monitoring provides valuable data for hazard assessment, evaluation of building conditions, and full-scale testing.

Damage Assessment of the 2010 Chile Earthquake and Tsunami Using Terrestrial Laser Scanning

In the wake of the 2010 Chile earthquake and tsunami, a reconnaissance survey recorded earthquake and tsunami damage using terrestrial laser scanning (TLS), which is capable of detecting details that most traditional reconnaissance methods cannot. TLS enables precise measurements of structural deformations and damage (including shear cracking of concrete walls, concrete spalling, and damage of rebars), as well as soil deformations and damage (including erosion, scour, liquefaction, lateral spread, slope failure, and ground displacement). Advanced measurements such as minute structural rotations, spatial distribution of cracks, volumetric and positional change calculations can also be obtained. Herein, we present various types of detailed measurements and analyses using TLS data obtained at several sites that were damaged by the earthquake and/or tsunami in Concepción, Constitución, Dichato, and Talcahuano. Moreover, this high-resolution data has enabled a unique avenue for virtual, post-visit analysis, providing additional insights that were not readily observable during the field visit.

Evaluation of landslide susceptibility mapping techniques using lidar-derived conditioning factors (Oregon case study)

ABSTRACT Landslides are a significant geohazard, which frequently result in significant human, infrastructure, and economic losses. Landslide susceptibility mapping using GIS and remote sensing can help communities prepare for these damaging events. Current mapping efforts utilize a wide variety of techniques and consider multiple factors. Unfortunately, each study is relatively independent of others in the applied technique and factors considered, resulting in inconsistencies. Further, input data quality often varies in terms of source, data collection, and generation, leading to uncertainty. This paper investigates if lidar-derived data-sets (slope, slope roughness, terrain roughness, stream power index, and compound topographic index) can be used for predictive mapping without other landslide conditioning factors. This paper also assesses the differences in landslide susceptibility mapping using several, widely used statistical techniques. Landslide susceptibility maps were produced from the aforementioned lidar-derived data-sets for a small study area in Oregon using six representative statistical techniques. Most notably, results show that only a few factors were necessary to produce satisfactory maps with high predictive capability (area under the curve >0.7). The sole use of lidar digital elevation models and their derivatives can be used for landslide mapping using most statistical techniques without requiring additional detailed data-sets that are often difficult to obtain or of lower quality.

Post-earthquake and tsunami 3D laser scanning forensic investigations

The recent Japanese earthquake and tsunami is one of several recent, destructive events that has provided critical engineering information regarding the performance of buildings, bridges, walls, roadways, etc. during intense loading. 3D laser scanning technology provides a valuable tool to acquire perishable information and preserve the scene digitally for post-disaster assessment. This paper discusses the challenges and benefits for use of 3D laser scanning on post-disaster reconnaissance efforts. This paper also focuses on special considerations when performing scanning work in post-disaster environments. Because of the limited time available to make critical decisions, it is important for personnel to know optimal procedures during planning, field reconnaissance, collaboration, data acquisition, processing, and analysis. Examples from recent events illustrate the power of this revolutionary tool in forensic investigations.