William E. Carter

Airborne laser swath mapping shines new light on Earth's topography

Airborne Laser Swath Mapping (ALSM) now makes it possible to delineate the physical features of the surface of Earth on spatial scales as fine as a few decimeters horizontally and a few centimeters vertically As a result, Earth scientists may finally be able to answer long-standing scientific questions about such surficial processes as erosion, faulting, volcanism, and plate motion. Information on surface relief, drainage patterns, and vegetation, critical to understanding the evolution of ecologically sensitive areas, can be collected over hundreds of square kilometers in a period of days. Information collected by ALSM can also be used to address a wide variety of engineering issues, such as developing and managing natural resources7semi; mitigating the impacts of such natural disasters as floods, hurricanes, tornados, landslides, and sinkholes; and building and maintaining transportation infrastructure.

Geodetic laser scanning

Producing surface maps at submeter resolution, even over heavily forested terrain, GLS can reveal the fine structure of such features as faults, landslides, and drainage patterns.

Variations in the Rotation of the Earth

Variations in the earths rotation (UT1) and length of day have been tracked at the submillisecond level by astronomical radio interferometry and laser ranging to the LAGEOS satellite. Three years of regular measurements reveal complex patterns of variations including UT1 fluctuations as large as 5 milliseconds in a few weeks. Comparison of the observed changes in length of day with variations in the global atmospheric angular momentum indicates that the dominant cause of changes in the earths spin rate, on time scales from a week to several years, is the exchange of angular momentum between the atmosphere and the mantle. The unusually intense El Ni�o of 1982-1983 was marked by a strong peak in the length of day.

Ancient Maya Regional Settlement and Inter-Site Analysis: The 2013 West-Central Belize LiDAR Survey

During April and May 2013, a total of 1057 km2 of LiDAR was flown by NCALM for a consortium of archaeologists working in West-central Belize, making this the largest surveyed area within the Mayan lowlands. Encompassing the Belize Valley and the Vaca Plateau, West-central Belize is one of the most actively researched parts of the Maya lowlands; however, until this effort, no comprehensive survey connecting all settlement had been conducted. Archaeological projects have investigated at least 18 different sites within this region. Thus, a large body of archaeological research provides both the temporal and spatial parameters for the varied ancient Maya centers that once occupied this area; importantly, these data can be used to help interpret the collected LiDAR data. The goal of the 2013 LiDAR campaign was to gain information on the distribution of ancient Maya settlement and sites on the landscape and, particularly, to determine how the landscape was used between known centers. The data that were acquired through the 2013 LiDAR campaign have significance for interpreting both the composition and limits of ancient Maya political units. This paper presents the initial results of these new data and suggests a developmental model for ancient Maya polities.

Now You See It… Now You Don’t: Understanding Airborne Mapping LiDAR Collection and Data Product Generation for Archaeological Research in Mesoamerica

In this paper we provide a description of airborne mapping LiDAR, also known as airborne laser scanning (ALS), technology and its workflow from mission planning to final data product generation, with a specific emphasis on archaeological research. ALS observations are highly customizable, and can be tailored to meet specific research needs. Thus it is important for an archaeologist to fully understand the options available during planning, collection and data product generation before commissioning an ALS survey, to ensure the intended research questions can be answered with the resultant data products. Also this knowledge is of great use for the researcher trying to understand the quality and limitations of existing datasets collected for other purposes. Throughout the paper we use examples from archeological ALS projects to illustrate the key concepts of importance for the archaeology researcher.

Improvements in absolute gravity observations

In the absolute gravity instruments developed by the Joint Institute for Laboratory Astrophysics (JILA) (Zumberge et al., 1982; Niebauer et al., 1986), the release of the dropped object induces systematic vibrations in the floor-gravimeter system. These vibrations can cause significant errors in the observed time-distance values from which the gravitational acceleration is computed. Detailed study of the vibrations affecting the gravity observations shows them to contain random noise and site dependent systematic components, which can be modeled by decaying sinusoids in the range of 10 to 120 Hz. This paper discusses (1) a mathematical filtering method to correct the observed time-distance array by identifying and removing all non-random signals from each individual drop, (2) upgrades of the gravimeter controller, which allow the collection of the data required to implement the mathematical filtering, and (3) mechanical filtering experiments using shock dampening pads and braces to minimize the vibrations. The maximum correction to observed gravity has been 23 μGal using the mathematical filter; typical corrections are in the 2–7 μGal range. The use of the shock dampening devices alone resulted in a three-fold reduction in the amplitudes and decay times of the systematic vibrations.

SLEEP ELECTROENCEPHALOGRAPHIC‐ELECTROOCULOGRAPHIC CHARACTERISTICS OF CHRONIC MARIJUANA USERS: PART I

The sleep electroencephalogram-electrooculogram (EEG-EOG) is increasingly recognized as a particularly sensitive tool for evaluating the effects of drugs, especially drugs that affect the central nervous system. Use of the waking or sleep EEG is one of the few reasonably direct, nonintrusive methods of monitoring central nervous system activity in man. The sleep EEG-EOG has several advantages over the waking EEG in evaluations of drugs. First, there are at least two distinct states of consciousness during sleep, rapid eye movement (REM) sleep and non-REM (NREM) sleep, and they make possible the assessment of drug effects under a greater variety of natural conditions than is true during wakefulness. Second, the sleep EEG-EOG is more clearly organized than the waking EEG, and sleep brain wave patterns can be easily and reliably categorized as belonging to one of five distinct stages of sleep: NREM stages 1, 2, 3, and 4 and stage-1 REM. Again, the natural variety in the sleep EEGEOG permits a more extensive evaluation of drug effects on brain activity. Furthermore, the relatively clear organization of the characteristic sleep stage patterns allows easier detection of anomalies than does the mixed-frequency activity of the waking EEG. Third, the sleep EEG-EOG is characterized by the periodic occurrence of several distinct wave forms, such as a, ,ti. and 6 waves, sleep spindles, K complexes, and eye movements, that can be examined for subtle changes. Fortunately, there now exist automated methods for detailed quantitative description and analyses of these fundamental sleep EEG-EOG wave forms. Marijuana and its major active constituent tetrahydrocannabinol (THC) are presumed to affect the central nervous system because of their effects on certain physical and mental functions. Present knowledge concerning the shortand long-term effects of these agents in humans is incomplete and confusing. Studies

Predicting Small Target Detection Performance of Low-SNR Airborne Lidar

Recent technological advances in the performance of small micro-lasers and multi-channel multi-event photo-detectors have enabled the development of experimental airborne lidar (light detection and ranging) systems based on a low-SNR (LSNR) paradigm. Due to dense point spacing (tens of points per square meter) and sub-decimeter range resolution, LSNR lidar can likely enable detection of meter-scale targets that would go unnoticed by traditional lidar technology. Small vehicle obstructions and other similar targets in the beach and littoral zones are of particular interest, because of LSNR lidars applicability to the near-shore environment and the general desire to improve detection of antivehicle and antipersonnel obstacles in the coastal zone. A target detection procedure is presented that exploits the detailed information available from LSNR lidar data while diminishing the effect of spurious noise events. Consideration is given to detection in both topographic and bathymetric scenarios. Data sets for target detection analysis are supplied by a numerical sensor simulator developed at the University of Florida. Target detection performance is evaluated as a function of environmental characteristics, such as water clarity and depth, and system parameters, specifically transmitted pulse energy and laser pulse repetition frequency. Analysis of results with regards to consideration for future system design is discussed.

Capability Assessment and Performance Metrics for the Titan Multispectral Mapping Lidar

In this paper we present a description of a new multispectral airborne mapping light detection and ranging (lidar) along with performance results obtained from two years of data collection and test campaigns. The Titan multiwave lidar is manufactured by Teledyne Optech Inc. (Toronto, ON, Canada) and emits laser pulses in the 1550, 1064 and 532 nm wavelengths simultaneously through a single oscillating mirror scanner at pulse repetition frequencies (PRF) that range from 50 to 300 kHz per wavelength (max combined PRF of 900 kHz). The Titan system can perform simultaneous mapping in terrestrial and very shallow water environments and its multispectral capability enables new applications, such as the production of false color active imagery derived from the lidar return intensities and the automated classification of target and land covers. Field tests and mapping projects performed over the past two years demonstrate capabilities to classify five land covers in urban environments with an accuracy of 90%, map bathymetry under more than 15 m of water, and map thick vegetation canopies at sub-meter vertical resolutions. In addition to its multispectral and performance characteristics, the Titan system is designed with several redundancies and diversity schemes that have proven to be beneficial for both operations and the improvement of data quality.

Predicting Topographic and Bathymetric Measurement Performance for Low-SNR Airborne Lidar

Government and commercial airborne light detection and ranging (lidar) systems have enabled extensive measurements of the Earths surface and land cover over the past decade. There is much interest, however, in employing smaller lidar systems that require less power to enable sensing from small unmanned aerial vehicles or satellites. Technological advances in the performance of small microlasers and photodetector sensitivity have recently enabled the development of experimental airborne lidar systems with low signal-to-noise ratios (LSNRs). Recent government and academic prototypes have indicated that LSNR airborne lidars could significantly increase the fidelity of terrain reconstruction over what is possible with existing conventional lidars. Thus, there is a need to build up a modeling capability for such systems in order to aid in future system and mission design. A numerical sensor simulator has been developed to model the expected returns from LSNR microlaser altimeter systems and predict their performance. Both optical and signal processing system components are considered, along with other factors, including atmospheric effects and surface conditions. Topographic (solid Earth) and bathymetric (littoral zone) measurement scenarios are considered. The analysis of topographic simulation data focuses on the effect of solar noise on SNR and elevation accuracy while bathymetric performance is evaluated with regard to water depth and scan angle for different water clarities. The mission conditions chiefly responsible for limiting the performance of LSNR lidar are discussed in detail, along with suggestions for further algorithm development and system performance evaluation.