THE THEORY AND APPLICATION OF THE STRUCTURE LIGHT ENGINEERING SURVEYING BASED ON A LASER THEODOLITE WITH THREE FREEDOMS OF ROTATION

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The theory and application of the structure light engineering surveying based on a laser theodolite with three freedoms of rotation

The concepts of “confining structure” and structure light are illuminated in this paper. A laser theodolite with three freedoms of rotation, which is aimed at “confining structure”, is developed. Various scanning modes and their mathematical models based on laser theodolite with three freedoms of rotation are discussed. According to the features of a huge object the structure light engineering surveying based on laser theodolite with three freedoms of rotation is determined as the main method in an actual application. The observation of four sound concrete posts and forced centering plates. Subsequently, it is transformed into the huge object coordinate system. The scanning mode with plumb plane is selected as the main mode in the whole work. And other assistant methods, such as close range photogrammetry and the method of using reflection sheet, are applied to the work of “scanning dead angle”. At last, a surveying accuracy estimation of this method is done and a surveying accuracy test is finished. It can be concluded that the structure light engineering surveying based on laser theodolite with three freedoms of rotation is considered to be an effective and applied method, and has many superiority to some other surveying methods in the work of surveying “confining structure”.     

Lasers and satellites: A geodetic application

Experiments photographing satellite reflected laser pulses have been made to demonstrate the feasibility of using an earth-based light source to illuminate satellites. The reflection was also recorded photoelectrically for range information. The reflections are photographed against stellar backgrounds from which the angular positions of the satellites relative to the laser site can be determined. With the angular information and the range data from the laser-illuminator, the position of the satellite in space is uniquely determined. When other widely separated laser-camera sites make simultaneous observations, the location of these sites relative to the “control” site can be found.     

Polarization of reflected light as a function in remote sensing of sea state

Polarizaton characteristics of completely diffuse light reflected from a wind roughened sea surface and its total reflectance are studied for various wind speeds on the assumption that distribution of wave slopes around their mean is Gaussian. The angular distribution of diffuse reflectance and polarization status of reflected light are also estimated with a view to exploring possibilities of using these parameters for remote sensing of sea state from a satellite, aircraft or an observation tower. The efficiency of Brewster’s angle technique in eliminating reflected light from the sea surface radiance for remote sensing of subsurface material is examined for non flat sea surface in the light of these results. the results show that the diffuse light reflected from the sea surface contains information on the sea state in the form of its status of polarization and can be used as an observational tool in remote sensing of sea state. The scope and limitations of the method proposed are discussed.     

Mapping for Cycle Touring in Britain; Past,Present, and a Possible Future

Abstract

The Lack hitherto of studies of cycle-touring mapping in Britain is noted, and some basic attributes of cycle touring, including speed, daily distance, gradients and wind, are described. Essential and desirable qualities for a cycle-touring map are enumerated, including the need to depict all rural routes available to cyclists; it is concluded that the optimum scale is in the range 1:100 000–1:126 720, and that relief should by contours at an interval not greater than 30 metres. National mapping in the optimum scale range which were published after 1945 are then reviewed, and reasons suggested as to why none has been kept in print. The mapping available for cycle touring in Britain in 2001 is Ordnance Survey (OS) 1:50 000 Landranger series contains all the necessary information, it is too bulky to be suitable; and that most of the other maps published in the optimum scale range have inadequate relief information and all offer very limited geographical cover. The potential competition for the OS 1:50 000 from a national map series in the optimum scale range is acknowledged, and an outline specification for a 1:125 000 series is described, which seeks to minimize that competiton whilst providing all the necessary information for cycle touring.     

Statistical analysis of refractive index through the troposphere and the stratosphere

The main environmental problem in tracking a satellite through the atmosphere is in finding the most probable value of the mean refractive index. In this paper, the mean refractive index is computed as a four-part model. The troposphere is treated as one altitude range from sea level to 9 kilometers, and the stratosphere is divided into three altitude ranges, 9 to 18, 18 to 27, and 27 to 36 kilometers. At 36 kilometers, the N-value is approximately equal to two and reduces rapidly to zero. By the use of theEssen formula in radio wave application and the modifiedKohlrausch formula in light wave application, point-to-point values of the refractive index are computed through these altitude ranges. The polynomial expansion of second order from the basic exponential function is selected as the model, and the curve-fitting adjustments of the computed values are established separately to each altitude range to obtain coefficients A, B, and C. A model based on the U. S. Standard Atmosphere, 1962, is used as the reference to which four sets of actual soundings made in Lihue, Hawaii and Fairbanks, Alaska on February 3 and July 2, 1966, are compared. The results show that the parabolic adjustment has a very high reliability. In the use of standard atmosphere, the standard error of the refractive index through the total altitude range of 0 to 36 kilometers, and at the 70° zenith distance, equal only ±7 millimeters when radio waves are utilized, and ±3 millimeters when light waves are utilized. Paper presented at Conference on Refraction Effects in Geodesy and Electronic Distance Measurement, University of New South Wales, 5–8 November 1968. Hawaii Institute of Geophysics Contribution No. 239.     

Measuring tree stem diameters using intensity profiles from ground-based scanning lidar from a fixed viewpoint

This paper presents a method for using the intensity of returns from a scanning light detection and ranging (lidar) system from a single viewing point to identify the location and measure the diameter of tree stems within a forest. Such instruments are being used for rapid forest inventory and to provide consistent supporting information for airborne lidars. The intensity transect across a tree stem is found to be consistent with a simple model parameterised by the range and diameter of the trunk. The stem diameter is calculated by fitting the model to transect data. The angular span of the stem can also be estimated by using a simple threshold where intensity values are tested against the expected intensity for a stem of given diameter. This is useful when data are insufficient to fit the model or the stem is partially obscured. The process of identifying tree positions and trunk diameters is fully automated and is shown to be successful in identifying a high proportion of trees, including some that are partially obscured from view. The range and bearing to trees are in excellent agreement with field data. Trunk angular span and diameter estimations are well correlated with field measurements at the plot scale. The accuracy of diameter estimation is found to decrease with range from the scanning position and is also reduced for stems subtending small angles (less than twice the scanning resolution) to the instrument. A method for adjusting survey results to compensate for trees missed due to obscuration from the scanning point and the use of angle count methods is found to improve basal area estimates and achieve agreement within 4% of field measurements.     

New interferometric techniques for measuring horizontal earth crustal movements

An interferometer using modern interferometric techniques has been developed at ZIPE, which allows the measurement of distances of more than 1 km. The interferometric equipment was designed for comparing distances of different lengths and directions and is appropriate for testing horizontal earth crustal movements. The new interferometer is based on Michelson’s interferometer using collimated light. The interference fringes are received by means of photoelectric detectors and can be observed visually by an oscilloscope. The duration of an interference signal need be only 1 ms and the corresponding path difference is registered by printing. In order to get such interferograms, the path difference of the two beams is periodically changed within an effective range of 8 mm, whilst the total difference between the beams can reach an amount of 1 m. The interferometer has been tested on the Potsdam International Standard Base Line up to a distance of 2.7 km.     

The design and the development of a hyperspectral and multispectral airborne mapping system

Flexible and cost-effective tools for rapid image acquisition and natural resource mapping are needed by land managers. This paper describes the hardware and software architecture of a low-cost system that can be deployed on a light aircraft for rapid data acquisition. The Hyperspectral and Multispectral Cameras for Airborne Mapping (HAMCAM) was designed and developed in the Geospatial Laboratory for Environmental Dynamics at the University of Idaho as a student-learning tool, and to enhance the existing curriculum currently offered. The system integrates a hyperspectral sensor with four multispectral cameras, an Inertial Navigation System (INS), a Wide Area Augmentation System (WAAS)-capable Global Positioning System (GPS), a data acquisition computer, and custom software for running the sensors in a variety of different modes. The outputs include very high resolution imagery obtained in four adjustable visible and near-infrared bands from the multispectral imager. The hyperspectral sensor acquires 240 spectral bands along 2.7 nm intervals within the 445–900 nm range. The INS provides aircraft pitch, roll and yaw information for rapid geo-registration of the imagery. This paper will discuss the challenges associated with the development of the system and the integration of components and software for implementation of this system for natural resource management applications. In addition, sample imagery acquired by the sensor will be presented.     

A geopotential error analysis for a non planar satellite to satellite tracking mission

This study is concerned with gravity field recovery from low-low satellite to satellite range rate data. Compared against a coplanar mission an improvement is predicted in errors associated with certain parts of the geopotential by the separation of the orbital planes of the two satellites. Using Hill's equations an analytical scheme is developed to model the range rate residuals. It is flexible enough to model the residuals between pairs of satellites in the same orbital plane or whose planes are separated in right ascension. This scheme should allow the possibility of larger planar separations than previously since no small angle approximation is made. The effects of such an orientation on gravity field recovery can therefore be analysed by means of an extensive error analysis. The results of this analysis indicate that a significant improvement in the errors of the near sectorial coefficients are obtained when the satellite's orbital planes are separated. Received: 9 April 1996; Accepted: 26 September 1996     

Effect of the SRTM global DEM on the determination of a high-resolution geoid model: a case study in Iran

Any errors in digital elevation models (DEMs) will introduce errors directly in gravity anomalies and geoid models when used in interpolating Bouguer gravity anomalies. Errors are also propagated into the geoid model by the topographic and downward continuation (DWC) corrections in the application of Stokes’s formula. The effects of these errors are assessed by the evaluation of the absolute accuracy of nine independent DEMs for the Iran region. It is shown that the improvement in using the high-resolution Shuttle Radar Topography Mission (SRTM) data versus previously available DEMs in gridding of gravity anomalies, terrain corrections and DWC effects for the geoid model are significant. Based on the Iranian GPS/levelling network data, we estimate the absolute vertical accuracy of the SRTM in Iran to be 6.5 m, which is much better than the estimated global accuracy of the SRTM (say 16 m). Hence, this DEM has a comparable accuracy to a current photogrammetric high-resolution DEM of Iran under development. We also found very large differences between the GLOBE and SRTM models on the range of −750 to 550 m. This difference causes an error in the range of −160 to 140 mGal in interpolating surface gravity anomalies and −60 to 60 mGal in simple Bouguer anomaly correction terms. In the view of geoid heights, we found large differences between the use of GLOBE and SRTM DEMs, in the range of −1.1 to 1 m for the study area. The terrain correction of the geoid model at selected GPS/levelling points only differs by 3 cm for these two DEMs.     

Precise position determination using a Galileo E5 single-frequency receiver

The European Galileo system offers one dedicated signal that is superior to all other signals currently available in space, namely the broadband signal E5. This signal has a bandwidth of at least 51 MHz using an AltBOC modulation. It features a code range noise at centimeter level. Additionally, the impact of multipath effects on this signal is significantly lower compared to all other available GNSS signals. These unique features of Galileo E5 drastically improve the precision of code range measurements and hence enable precise single-frequency positioning. Certain scientific and non-scientific applications in the positioning domain could likely benefit from the exploitation of E5 measurements. A positioning approach based on an additive combination of code range and carrier phase measurements (CPC—“code-plus-carrier”) to eliminate the ionospheric delay could be used to perform precise positioning over long distances. Unfortunately, this derived observable contains the ambiguity term as an additional unknown what normally requires longer observation windows in order to allow sufficient convergence of the ambiguity parameters. For this reason, a rapid convergence algorithm based on Kalman filtering was implemented in addition to the conventional CPC approach that is also discussed. The CPC-based results yield a positioning precision of 2–5 cm after a convergence time of about 3 h. The rapid convergence filter allows fixing the ambiguity terms within a few minutes, and the obtained position results are at the sub-decimeter level. Regarding one selected test, real data from Galileo experimental satellite GIOVE A were used in order to confirm our assumptions. However, since the current Galileo constellation is not sufficient for real-world positioning trials yet, all major results are based on simulated data.     

北斗B1C、B2a信号非理想性分析及接收约束建议

卫星导航信号的非理想性会导致不同接收机之间出现测距偏差,是影响卫星导航系统服务精度和完好性的重要因素。首先,针对北斗系统B1C、B2a新体制信号的非理想性进行分析,利用大口径天线采集了全部北斗三号在轨卫星播发的B1C、B2a信号（共27颗卫星）,评估了不同接收带宽、码鉴相间距下测距偏差的大小与变化特点;然后,以双频多星座星基增强服务应用为例,分析了两个信号在相应接收机中的设计约束条件。研究结果发现,在接收机常用的参数范围内,B1C、B2a信号非理想性引入的测距偏差分别不超过0.68 m、0.44 m;在测距偏差小于0.1 m的性能约束下,B1C、B2a信号可用的约束条件参数范围优于国际民航标准草案中的相关要求。     

Performance analysis of a stand-alone high-sensitivity receiver

The use of GPS for personal location using wireless devices requires satellite signal measurements both outdoors and indoors. In the outdoor environment propagation paths may range from line-of-sight to shaded or blocked. The indoor environment may range from single-floor wooden constructions to high-rise buildings and underground facilities. In this paper, a high-sensitivity receiver which operates in unaided stand-alone mode is tested under a range of shaded and blocked signal environments, ranging from residential outdoor areas to urban canyons and residential houses. The measurement analysis is performed in both the observation and position domains. The results show that the receiver tested is able to yield measurements with C/N₀ degradations in excess of 20 dB-Hz, as compared to line-of-sight measurements. Position results are a function of the geometry of the remaining satellites, which in turn is a function of the environment. Electronic Publication     

SMALL FORMAT AERIAL SURVEYS FROM LIGHT AND MICROLIGHT AIRCRAFT

Small format (SF) cameras, fitted to light or microlight aircraft, can provide an economic and convenient alternative to the more expensive conventional mapping systems. Further advantages accrue from the use of wider aperture lenses, an extensive range of easily available films and simplijed processing. These advantages can be exploited by employing light aircraft for small survey missions, such as map revision, and desktop photogrammetric systems dedicated to handling SF imagery. In this paper, an account is given of a research study involving SF map revision survey photography, using a modern microlight aircraft and a 70 mm metric camera.     

On the path curvature of electromagnetic waves

To facilitate the calculation of atmospheric refraction from radiometeorological sounding observations, the coefficients of refraction for light and microwaves have been expressed in the general form k=A.p+B.U+(C·p+D·U) dt/dz+E·dU/dz where p is total pressure, U is relative humidity and A, B, C, D and E are tabulated functions of temperature t. Three-place tables are given in metric units for the temperature range −10°C to +30°C. The paper includes a general discussion of the variation of refraction with weather, and outlines computation procedures for electromagnetic measurement of long lines on the basis of radiosonde data.     

DMSP-OLS与NPP-VIIRS夜间灯光数据测算统计指标能力评估——以京津冀地区县域GDP、人口及能源消耗为例

夜间灯光数据记录了地球表面的人造灯光强度,是估计社会统计指标的有效手段之一。为了评估DMSP-OLS和NPP-VIIRS 2种夜间灯光数据对社会统计指标的模拟潜力,采用4种常用的灯光校正方法分别对2种夜间灯光数据进行灯光饱和性校正,根据校正后的夜间灯光数据分别建立与京津冀地区县域GDP、人口和能源消耗3种社会统计指标间的线性回归模型,从模型拟合的相关系数、F统计量值与概率p值中分析并评价了2种夜间灯光数据对GDP、人口和能源消耗3种社会统计指标的测算能力。本文研究结果表明：EANTLI法是2种夜间灯光数据的最佳校正方式,而HSI法不适用于夜间灯光数据校正后与县域社会统计指标的线性关系拟合2种夜间灯光数据对GDP的拟合效果都较好,NPP-VIIRS夜间灯光数据估算社会统计指标的拟合能力要优于DMSP-OLS数据。     

Multiple reference consistency check for LAAS: a novel position domain approach

Since the traditional Maximum Likelihood-based range domain multiple reference consistency check (MRCC) has limitations in satisfying the integrity requirement of CAT II/III for civil aviation, a Kalman filter-based position domain method has been developed for fault detection and exclusion in the Local Area Augmentation System MRCC process. The position domain method developed in this paper seeks to address the limitations of range domain-based MRCC by focusing not only on improving the performance of the fault detection but also on the integrity risk requirement for MRCC. In addition, the issue of the stability of the Kalman filter in relation to the position domain approach is considered. GPS range corrections from multiple reference receivers are fused by the adaptive Kalman filter at the master station for detecting and excluding the single reference receiver’ failure. The performance of the developed Kalman filter-based MRCC has been compared with the traditional method using experimental data. The results reveal that the vertical protection level is slightly better in the traditional method compared with the developed Kalman filter-based approach under the fault-free case. However, the availability can be improved to over 97% in the proposed method relative to the traditional method under the single-fault case. Furthermore, the fault-tolerant positioning result with an accuracy improvement of more than 32% can be achieved even if different fault types are considered under the single-fault case. In particular, the algorithm can be a candidate option as an augmentable complement for the traditional MRCC and can be implemented in a master station element of the LAAS integrity monitoring architecture.     

A six-camera digital video imaging system sensitive to visible,red edge,near-infrared,and mid-infrared wavelengths

This paper describes a six-camera multispectral digital video imaging system designed for natural resource assessment and shows its potential as a research tool. It has five visible to near-infrared light sensitive cameras, one near-infrared to mid-infrared light sensitive camera, a monitor, a computer with a multichannel digitizing board, a keyboard, a power distributor, an amplifier, and a mouse. Each camera is fitted with a narrowband interference filter, allowing the system to obtain imagery in the blue (447 – 455 nm), green (555 – 565 nm), red (625 – 635 nm), red edge (704 – 716 nm), near-infrared (814–826 nm), and mid-infrared (1631 – 1676 nm) regions of the electromagnetic spectrum. Analogue video acquired by this system is converted to digital format. Radiometric resolution of the imagery is 8-bit (pixel values range 0 – 255). Images obtained by the system can be evaluated individually and/or in combination with each other to assess natural resources.     

Measurement of distances by high frequency light signalling

Summary A source of light emils light, the intensity of which varies with a frequency which is kept constant by means of an oscillating quartz crystal. A plane mirror is placed at a distance of 10–30 km from the source of light. The mirror reflects the light back to a phototube placed in the neighbourhood of the source of light. The above-mentioned crystal controls the sensitivity of the tube, which thus varies with the same frequency as the source of light. Thereby, the electrical currents from the tube will vary with the distance, depending on whether the incoming light impulses are more or less timed to the cycles of sensitivity of the phototube. Thus the variation of the current is periodic with the distance. With the actual rate of crystal frequency, the same strength of current is repeated every 18th meter that the mirror is moved. When measuring distances the periodical change with the distance is employed as a scale. The size of the scale is once and for all determined from a known distance. A special arrangement causes the currents to reverse every 9th meter of change in distance. Thus the currents pass through zero and have their greatest rate of change in relation to a change in distance. The 0-points represent the division-lines of the scale of distance used. The constancy of the distance between the division-lines is directly dependent on the constancy of the frequency. The determination of a distance is accurate to about one in one million.