John S. Oldow

Shrub characterization using terrestrial laser scanning and implications for airborne LiDAR assessment

Sagebrush-steppe ecosystems across the United States Intermountain West are experiencing major structural and functional changes. Scientists and managers need effective technologies to understand such dynamic changes across broad spatial scales. We tested the capacity of terrestrial laser scanning (TLS) to automatically determine structural information of individual shrubs (principally Artemisia tridentata) and shrub canopies in eastern Washington, USA. Because current airborne LiDAR systems have technological constraints that may limit their utility in shrub-dominated ecosystems, we used the TLS data both in their basic form and to simulate high resolution discrete-return airborne LiDAR data with sample densities of 4 and 16 points m−2. Through spatial wavelet analysis we automatically detected the locations of up to 78% of all individual shrubs identified in the field and up to 88% of shrubs with a crown diameter > 1.5 m. Shrub height and canopy cover derived from TLS data were significantly correlated with field measurements (respectively, r2 = 0.94 and 0.51, p < 0.001, α = 0.05). Automated detection of individual shrub crown area using the high resolution simulated airborne LiDAR dataset was also significantly correlated with field measurements (r2 = 0.47, p ≤ 0.01). Our results indicate that TLS data are useful for automatic quantification of shrub structure and provide a glimpse to the utility of the next generation of small-footprint airborne LiDAR instruments in quantifying shrub biophysical parameters across broad areas.

Applications of airborne and terrestrial laser scanning to paleoseismology

Paleoseismic investigations aim to document past earthquake characteristics such as rupture location, frequency, distribution of slip, and ground shaking intensity—critical parameters for improved understanding of earthquake processes and refined earthquake forecasts. These investigations increasingly rely on high-resolution ( 2 /m. This situation refines interpretations of PBR exhumation rates and thus their effectiveness as paleoseismometers. Given that earthquakes disrupt Earth9s surface at centimeter to meter scales and that depositional and erosional responses typically operate on similar scales, ALS and TLS provide the absolute measurement capability sufficient to characterize these changes in challenging geometric arrangements, and thus demonstrate their value as effective analytical tools in paleoseismology.

Assessment of the uncertainty budget and image resolution of terrestrial laser scans of geomorphic surfaces

Terrestrial laser scanner (TLS) images provide assessment of geomorphic surfaces at a centimeter scale, but for quantitative analysis require an understanding of the uncertainty budget and the limit of image resolution. We conducted two experiments to assess contributions of instrumental, georeferencing, and surface modeling methods to the uncertainty budget and to establish the relation between reference network uncertainty and the repeatability and resolution of imaged natural surfaces. Combinations of Riegl LMS-Z620 and LPM-800HA instruments were used to image fault scarps and erosional ravines in Panamint Valley and the San Gabriel Mountains of California (USA), respectively. In both experiments, a control network of reflectors was surveyed using total station (TS) and georeferenced with the Global Navigation Satellite System (GNSS) in real time kinematic (RTK) and static (S) modes in the first and second experiment, respectively. For successive scans, we tested the impact of using a fixed network of control reflectors and scan positions versus using variable scan positions in a fixed reflector network and variable scan and reflector network configurations. The geometry of the reflector network in both experiments was established using a TS to within ±0.005 m and in addition to ±0.006 m using S-GNSS occupations during the second experiment. TLS repeatability in a local frame is ±0.028 m, with uncertainty increasing to ±0.032 m and ±0.038 m using S-GNSS and RTK-GNSS, respectively. Point-cloud interpolation, where vegetation effects were mitigated, contributed ±0.01 m to the total error budget. We document that the combined uncertainty for the reference network and surface interpolation represents the repeatability of an imaged natural surface.

Outlining a strategic vision for terrestrial geodetic imaging

Charting the Future of Terrestrial Laser Scanning in the Earth Sciences and Related Fields; Boulder, Colorado, 17–19 October 2011 A workshop hosted by UNAVCO and funded by the U.S. National Science Foundation (NSF) brought together 80 participants representing a spectrum of research fields with the objective of outlining a strategic vision for the future of terrestrial geodetic imaging as applied to a broad range of research activities at all levels of the community. Earth science investigations increasingly require accurate representation of the Earth surface using three-dimensional data capture, display, and analysis at a centimeter scale to quantitatively characterize and model complex processes. Recognizing this community need, researchers at several universities and UNAVCO established the NSF-funded Interdisciplinary Alliance for Digital Field Data Acquisition and Exploration (INTERFACE) project to support a terrestrial laser scanning (TLS) instrument pool and data collection expertise now based at UNAVCO

Late Cenozoic displacement transfer in the eastern Sylvania Mountain fault system and Lida Valley pull-apart basin, southwestern Nevada, based on three-dimensional gravity depth inversion and forward models

The Sylvania Mountain fault system is a major left-oblique structure that extends east from the Furnace Creek–Fish Lake Valley fault in southwestern Nevada (USA). The system interacts with a series of north-northeast–striking structures that bound a rectilinear pull-apart basin, Lida Valley, and serve as part of a displacement transfer system relaying slip from the eastern California shear zone to the Walker Lane. On the basis of gravity analysis, the Lida Valley basin is internally dissected by a complex system of faults. The subsurface basin morphology differs from north to south. Major extensional faults localized displacement in the north and formed deep basins, but in the south, displacement was distributed on widely spaced structures with modest displacement. Localized extension in the north is separated from the southern domain of distributed deformation by a west-northwest oblique-slip fault. The subsurface geometry of the basin was determined from a gravity survey with measurements depth inverted in three dimensions. Geologic cross sections were constructed and their gravity signatures forward modeled for compatibility with observations. Projections of mapped faults together with structures determined from gravity modeling were combined to construct the subsurface geometry of the Lida Valley fault system and to evaluate a fault displacement budget. By conserving fault slip on the array of structures, restoration of the pre-Neogene basement to a reference datum indicates a cumulative vertical displacement of 2.3–2.5 km since the onset of basin formation. Vertical displacement estimates were used to compute the horizontal component of extension, which ranges from 1.3 to 1.4 km.