Review of the development of laser fluorosensors for oil spill application

As laser fluorosensors provide their own source of excitation, they are known as active sensors. Being active sensors, laser fluorosensors can be employed around the clock, in daylight or in total darkness. Certain compounds, such as aromatic hydrocarbons, present in petroleum oils absorb ultraviolet laser light and become electronically excited. This excitation is quickly removed by the process of fluorescence emission, primarily in the visible region of the spectrum. By careful choice of the excitation laser wavelength and range-gated detection at selected emission wavelengths, petroleum oils can be detected and classified into three broad categories: light refined, crude or heavy refined.

This paper will review the development of laser fluorosensors for oil spill application, with emphasis on system components such as excitation laser source, and detection schemes that allow these unique sensors to be employed for the detection and classification of petroleum oils. There have been a number of laser fluorosensors developed in recent years, many of which are strictly research and development tools. Certain of these fluorosensors have been ship-borne instruments that have been mounted in aircraft for the occasional airborne mission. Other systems are mounted permanently on aircraft for use in either surveillance or spill response roles.     

Glonass Laser Ranging Accuracy With Satellite Signature Effect

GLONASS satellites have been tracked by the worldwide laser ranging networkas well as by the GLONASS-borne microwave-based technique. Owing to thelarge size of their corner cube reflector arrays, the amount of ranging data is enough to determine their orbits from laser ranging data alone. We found, however, that the large size of the array affected the accuracy of measurement to an extent that is dependent on the characteristics of the ranging systems. An azimuthal variation of the reflector array response was also detected in observations from single-photon laser ranging. Orbital analysis reveals that the effect makes the measured range on average 22 mm shorter than expected in the absence of the large array, which explains more than half of the offset of 39 mm previously discovered between microwave and laser orbits.     

A 100 m laser strainmeter system installed in a 1 km deep tunnel at Kamioka, Gifu, Japan

We have installed a laser strainmeter system in a deep tunnel about 1,000 m below the ground surface at Kamioka, Gifu, Japan. The system consists of three types of independent interferometers: (1) an EW linear strainmeter of the Michelson type with unequal arms, (2) an NS-EW differential strainmeter of the Michelson type with equal arms and (3) a NS absolute strainmeter of the Fabry–Perot type. These are configured in L-shaped vacuum pipes, each of which has a length of 100 m. (1) and (2) are highly sensitive (order of 10⁻¹³ strain) and have wide dynamical range (10⁻¹³–10⁻⁶). Observations with strainmeters (1) and (2) started on June 11, 2003. (3) is a new device for absolute-length measurements of the order of 10⁻⁹ of a long-baseline (100 m) Fabry–Perot cavity by the use of phase-modulated light. This third strainmeter will be ready for operation before the end of 2004. The laser source of strainmeters (1) and (2) is a frequency-doubled YAG laser with a wavelength of 532 nm. The laser frequency is locked onto an iodine absorption line and a stability of 2 × 10⁻¹³ is attained. The light paths of the laser strainmeter system are enclosed in SUS304 stainless steel pipes. The inside pressure is kept to be 10⁻⁴ Pa. Consequently, quantitative measurement of crustal strains of the order of 10⁻¹³ can be attained by employing the laser strainmeter system of (1) and (2) at Kamioka. This resolving power corresponds to that of a superconducting gravimeter. Using the laser strainmeter system, we expect to determine parameters related to fluid core resonance, core modes and core undertone as well as other geodynamic signals such as slow strain changes caused by silent earthquakes or slow earthquakes.     

Toroidal free oscillations of the Earth observed by a ring laser system: a comparative study

In this study, we explore the potential of measuring systematically the Earth's free oscillations using ring laser gyro (RLG) vertical axis rotational records. The RLG that we use is the vertical axis G-ring laser system of the Geodetic Observatory Wettzell (Germany). In 2009, its signal-to-noise ratio was considerably improved over the broadband frequency range of seismic measurements. Since then, three large magnitude earthquakes have occurred (Samoa Islands 2009; Maule, Chile, 2010; and Tohoku, Japan, 2011), leading to the first direct observations of rotational ground motions induced by toroidal free oscillations of the Earth. We compare these G-ring laser observations with synthetic seismograms computed by summing normal modes. We also analyse amplitude spectra of real and synthetic data to aid in the interpretation of the observations. We show that several toroidal modes are detected by the G-ring laser for earthquakes with a moment magnitude M _W????8.0 and that our observations are in reasonable agreement with the synthetic spectra. We also report evidence for mode coupling in both translation and rotation spectra.     

Snow measurement by GPS interferometric reflectometry: an evaluation at Niwot Ridge,Colorado

Snow is a critical storage component in the hydrologic cycle, but current measurement networks are sparse. In addition, the heterogeneity of snow requires surveying larger areas to measure the areal average. We presented snow measurements using GPS interferometric reflectometry (GPS‐IR). GPS‐IR measures a large area (~100 m²), and existing GPS installations around the world have the potential to expand existing snow measurement networks. GPS‐IR uses a standard, geodetic GPS installation to measure the snow surface via the reflected component of the signal. We reported GPS‐IR snow depth measurements made at Niwot Ridge, Colorado, from October 2009 through June 2010. This site is in a topographic saddle at 3500 m elevation with a peak snow depth of 1.7 m near the GPS antenna. GPS‐IR measurements are compared with biweekly snow surveys, a continuously operating scanning laser system and an airborne light detection and ranging (LIDAR) measurement. The GPS‐IR measurement of peak snowpack (1.36–1.76 m) matches manual measurements (0.95–1.7 m) and the scanning laser (1.16 m). GPS‐IR has RMS error of 13 cm (bias = 10 cm) compared with the laser, although differences between the measurement locations make comparison imprecise. Over the melt season, when the snowpack is more homogenous, the difference between the GPS‐IR and the laser is reduced (RMS = 9 cm, bias = 6 cm). In other locations, the GPS and the LIDAR agree on which areas have more or less snow, but the GPS estimates more snow on the ground on tracks to the west (1.58 m) than the LIDAR (1.14 m). Copyright © 2011 John Wiley & Sons, Ltd.     

Determination of polar motion from satellite observations

Doppler observations of U.S. Navy Navigation Satellites have been used to determine the Earth's pole position for the period 1967 to July 1972. Recent results are competitive in accuracy with astronomic results and exhibit about 0".02 agreement with astronomic pole positions. The differences are no larger than those between independent calculations of pole positions based on astronomic data (BIHvs. ILS). For a two-day span of observations made by 18 Doppler stations the uncertainty in computed pole position corresponding to random errors in observation is 0".002. However, the results have systematic errors with various frequencies which are primarily due to uncertainties in the gravity coefficients. Since these errors are independent of those producing systematic errors in astronomic results, the two techniques are complementary. Recent results of computation of polar motion based on laser observations of artificial Earth satellites have also produced results having accuracies comparable to Doppler and astronomic results. The analysis of the laser observations is based on the effect of pole position on the apparent inclination of satellite orbits; on the other hand, since the Doppler observations are made on polar orbiting satellites, they are more sensitive to errors in the component of pole position which lies in the orbit plane. As a result of this difference, biases in Doppler and laser results may be different in size or character.     

工程勘察中激光三维扫描和建模技术研究

激光三维扫描和三维地质建模技术的应用,使得工程地质体的变形、沉降、扭转、位移勘察工作变得更加高效、快速和经济.简要介绍了逆向工程的基本思想,探讨了逆向工程在工程勘察中的应用模式,基于激光三维扫描仪器Trimble GS200和三维数据处理软件CATIA,阐述了工程勘察过程中数字模型的建立方法和图像数据的处理流程,并通过对处理结果的分析来完成工程勘察的目标.通过对一个实体数据实例的分析和模拟,实现了对实体表面地质数据的全面分析和动态监控.分析发现,联合应用激光三维扫描和三维地质建模技术,能够在河道变形分析、大坝位移与变形监测、飞机跑道路面勘察、桥梁变形监测等工程勘察工作中发挥作用,其发展前景非常广阔.     

Meteotsunami Manifestations in Geospheres

Izvestiya, Physics of the Solid Earth - The results of processing synchronous records from two laser strainmeters, a broadband seismograph, a laser nanobarograph, and a laser meter of hydrospheric...     

Ground-based lidar and atmospheric studies

This review considers the requirements and possibilities for the development of a ground-based network for long-term observations of the atmosphere. This network would be specifically designed to provide early detection of changes in the composition and structure of the stratosphere. The species and parameters identified as being important and amenable to ground-based measurements are summarized, as are the currently available techniques capable of making the required measurements. Ultraviolet laser remote sensing is identified as the most promising technique for the measurement of ozone and temperature profiles which are considered to have the highest priority for network measurements. The laser techniques, and the research at JPL Table Mountain Observatory, to implement ozone and temperature measurements are discussed in greater detail.     

Strain rotation coupling and its implications on the measurement of rotational ground motions

Spatial derivatives of the seismic wave field are known to be sensitive to various site effects (e.g., cavity effects, topography, and geological inhomogeneities). In this study, the focus is on strain rotation coupling that can cause significant differences between point measurements compared to array-derived rotational motions. The strain rotation coupling constants are estimated based on finite element simulations for inhomogeneous media as well as for the 3D topography around Wettzell, Germany (the location of the G ring laser). Using collocated array and ring laser data, the coupling constants of the ring laser itself are shown to be small. Several examples are shown to illustrate the order of magnitude that strain-induced rotation might have on the seismograms in the near field of volcanoes as well as in the far field and in the low-frequency spectrum (free oscillations).     

钠多普勒激光雷达回波光子数仿真及大气参数反演

钠多普勒激光雷达利用中层顶区域的钠原子作为示踪物,探测中层顶区域大气风场和温度剖面.本文主要分析钠多普勒激光雷达的探测原理和大气参数反演算法.利用MSISE和HWM93等大气模型给出背景大气温度、密度及风场,并给定钠原子数密度剖面,从激光雷达方程出发,模拟计算了激光雷达的瑞利散射和钠共振荧光散射回波光子数.利用模拟的回波光子数剖面数据,反演得到大气温度、视线风速和钠原子数密度剖面,反演结果与模拟计算用的背景参数符合很好,验证了这一反演方法的正确性.分析了激光频率偏移和激光线宽变化对反演精度的影响.     

数字化地震记录分析软件PITSA简介及使用说明

“九五”期间我们将建立一批数字化地震台站，紧接着就是数字化记录的常规处理和数字化资料的开发利用问题。这两方面的工作都离不开数字化记录的常规处理软件。由国际地震学和地球内部物理学协会（ＩＡＳＰＥＩ）和联合国科教文组织（ＵＮＥＳＣＯ）以及美国地震学会（ＳＳＡ）联合推荐的由Ｆ．ＳｃｈｅｒｂａｕｍａｎｄＪ．Ｊｏｈｎｓｏｎ完成的一套优秀的数字化分析处理软件ＰＩＴＳＡ（ＰｒｏｇｒａｍｍａｂｌｅＩｎｔｅｒａｃｔｉｖｅＴｏｏｌｂｏｘｆｏｒＳｅｉｓｍｏｌｏｇｉｃａｌＡｎａｌｙｓｉｓ）是一套比较适合我国广大地震工作者使用的软件。ＰＩＴＳＡ的特点是：①在普通微机（ＰＣ机）上安装使用，要求的微机和外部环境都很低，容易安装，占据的硬盘空间小（约２Ｍ）字节；②功能很强，如部分放大，震相拾取、求震级、定震中、分量旋转等常规分析工作它都能很好完成，进一步的分析处理工作如数值微分、积分、基线校正、谱分析、滤波、相关、Ｈｉｌｂｅｒｔ变换，旋转分量、偏振滤波、交义谱、相关谱、画质点运动图、各种模拟地震图的仿真等，它都能方便地实现；③它是菜单操作式软件，易学易用；④我们已有现成的软件，并已被一些地震工作者开发利用。鉴于以上优点，故我们特出版此专辑     

Ultra‐rapid topographic surveying for complex environments: the hand‐held mobile laser scanner (HMLS)

Terrestrial laser scanning is the current technique of choice for acquiring high resolution topographic data at the site scale (i.e. over tens to hundreds of metres), for accurate volume measurements or process modelling. However, in regions of complex topography with multiple local horizons, restricted lines of sight significantly hinder use of such tripod‐based instruments by requiring multiple setups to achieve full coverage of the area. We demonstrate a novel hand‐held mobile laser scanning technique that offers particular promise for site‐scale topographic surveys of complex environments. To carry out a survey, the hand‐held mobile laser scanner (HMLS) is walked across a site, mapping around the surveyor continuously en route. We assess the accuracy of HMLS data by comparing survey results from an eroding coastal cliff site with those acquired by a state‐of‐the‐art terrestrial laser scanner (TLS) and also with the results of a photo‐survey, processed by structure from motion and multi‐view stereo (SfM‐MVS) algorithms. HMLS data are shown to have a root mean square (RMS) difference to the benchmark TLS data of 20 mm, not dissimilar to that of the SfM‐MVS survey (18 mm). The efficiency of the HMLS system in complex terrain is demonstrated by acquiring topographic data covering ~780 m² of salt‐marsh gullies, with a mean point spacing of 4.4 cm, in approximately six minutes. We estimate that HMLS surveying of gullies is approximately 40 times faster than using a TLS and six times faster than using SfM‐MVS. © 2013 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd.     

青海湟水盆地活动断裂构造格架激光散斑模拟试验研究

将最新研究的湟水盆地断裂构造格架设置于合理的试验材料之上，进行激光散斑模型模拟试验，取得了断裂活动特征的量化显示结果，并用于评价区域地壳稳定性．     

High-frequency noise caused by wind in large ring laser gyroscope data

The large ring laser gyroscope at the Geodetic Observatory Wettzell provides unique data of the rotational component of seismic waves. Wind has been identified as a major source of noise at short periods below 5?min. Strong winds increase the level of detected background noise either through surface friction or through wind load on hill slopes. Since our G ring laser demonstrated a routinely achieved sensitivity for rotations of 10?picorad/s when averaged over 30?s, very small effects become detectable. Using a local finite element model and applying a digital terrain model with 25?m spatial resolution, the effect of local wind forces on tilt and horizontal rotations at the ring laser site was calculated. The transfer of forces by wind ram pressure or surface friction is strongly controlled by the resolution of the terrain model or the land use, respectively. The maximum deformation caused by real wind fields reaches a few tenths of nanorads for both tilt and horizontal rotation. While the tilts are too small to affect the ring laser measurements by a change in its inclination, the horizontal rotations can be detected by the ring laser if the signal builds up within a few seconds or tens of seconds. The comparison of the modelled rotation rate time series with measured ring laser data shows a reasonable agreement in amplitude and waveform, however the correction of the ring laser time series is limited by the crude sampling of the wind measurements.     

Horizontal rotation signals detected by “G-Pisa” ring laser for the M w = 9.0, March 2011, Japan earthquake

We report the observation of the ground rotation induced by the M _w = 9.0, 11th of March 2011, Japan earthquake. The rotation measurements have been conducted with a ring laser gyroscope operating in a vertical plane, thus detecting rotations around the horizontal axis. Comparison of ground rotations with vertical accelerations from a co-located force balance accelerometer shows excellent ring laser coupling at periods longer than 100?s. Under the plane wave assumption, we derive a theoretical relationship between horizontal rotation and vertical acceleration for Rayleigh waves. Due to the oblique mounting of the gyroscope with respect to the wave direction of arrival, apparent velocities derived from the acceleration/rotation rate ratio are expected to be always larger than or equal to the true wave propagation velocity. This hypothesis is confirmed through comparison with fundamental mode, Rayleigh-wave phase velocities predicted for a standard Earth model.     

Application of laser strainmenters to the study of earthquake physics

The paper considers possibilities of applying laser strainmeters for the study of earthquake physics. One of laser strainmeters is described. A high efficiency of using the laser strainmeters for the study of earthquakes and their precursors is shown. In records of the spaced laser strainmeters, anomalous deformations propagating from the east to the west with the speed comparable with that of migration of earthquakes were found.     

10-12秒精度激光测距问题的理论研究

随着空间大地测量技术观测精度的提高 ,需要激光测距理论模型适应目前和未来可预见的精度要求 .本文基于激光测距的基本原理 ,给出了太阳系质心参考系 (BRS)和地球质心参考系 (GRS)中的相对论激光测距的理论模型 ,对两种激光测距模型中有关引力时延的量级进行了估计 ,并给出了完整而自洽的时间尺度和时空坐标变换的理论公式 .根据最新的BRS和GRS系之间的时空坐标变换关系 ,在皮秒 (10 - 1 2 s)的精度下 ,推导出了在GRS中适合于所有激光测距问题的相对论模型 ,同时扩展了IERS推荐的激光测距模型的适用范围     

Assessing the performance of structure‐from‐motion photogrammetry and terrestrial LiDAR for reconstructing soil surface microtopography of naturally vegetated plots

Soil microtopography is a property of critical importance in many earth surface processes but is often difficult to quantify. Advances in computer vision technologies have made image‐based three‐dimensional (3D) reconstruction or Structure‐from‐Motion (SfM) available to many scientists as a low cost alternative to laser‐based systems such as terrestrial laser scanning (TLS). While the performance of SfM at acquiring soil surface microtopography has been extensively compared to that of TLS on bare surfaces, little is known about the impact of vegetation on reconstruction performance. This article evaluates the performance of SfM and TLS technologies at reconstructing soil microtopography on 6 m × 2 m erosion plots with vegetation cover ranging from 0% to 77%. Results show that soil surface occlusion by vegetation was more pronounced with TLS compared to SfM, a consequence of the single viewpoint laser scanning strategy adopted in this study. On the bare soil surface, elevation values estimated with SfM were within 5 mm of those from TLS although long distance deformations were observed with the former technology. As vegetation cover increased, agreement between SfM and TLS slightly degraded but was significantly affected beyond 53% of ground cover. Detailed semivariogram analysis on meter‐square‐scale surface patches showed that TLS and SfM surfaces were very similar even on highly vegetated plots but with fine scale details and the dynamic elevation range smoothed out with SfM. Errors in the TLS data were mainly caused by the distance measurement function of the instrument especially at the fringe of occlusion regions where the laser beam intersected foreground and background features simultaneously. From this study, we conclude that a realistic approach to digitizing soil surface microtopography in field conditions can be implemented by combining strengths of the image‐based method (simplicity and effectiveness at reconstructing soil surface under sparse vegetation) with the high accuracy of TLS‐like technologies. Copyright © 2015 John Wiley & Sons, Ltd.