THE DEFLECTION PRISM

Abstract

The optical principle of the deflection prism may not be known to all readers. Though there is nothing of very modern origin in the optics of a prism, as a wedge of very acute angle it possesses special powers which admit of useful adaptation to certain types of instrument. This application is a development of comparatively recent times. It will not be out of place, therefore, to make some reference to it in this Review.     

Error analysis of exterior orientation elements on geolocation for a Moon-based Earth observation optical sensor

ABSTRACT

The Moon is a potential new platform for Earth observation. The advantages of its large-scale observational scope, long temporal duration, and multi-layer detecting of the Earth will undoubtedly advance our understanding of the Earth system. To carry out the observations from a Moon-based optical sensor, the geolocation error caused by exterior orientation elements need to be investigated. This paper analyses the error effects of exterior orientation elements on geolocation for an optical sensor. To estimate the error, we present a geometric image model and utilise some parameters to measure the image offsets. Through a large number of numerical simulations, the results demonstrate that the image offsets are not obvious influenced by the distance and observation angle at mid-high latitude of the Moon and have linear correlation with the increasing errors of the exterior orientation elements. Further, the relationship between the spatial resolution and errors of exterior orientation elements are revealed. Finally, the error characteristics for Moon-based Earth observation are discussed. It is expected that the conclusion drawn in this paper could support the study of a Moon-based Earth observation optical sensor.     

A CHANCE CORRECTION OF A TRAVERSE

Abstract

It sometimes happens that from a point on a line of theodolite traverse two fixed points are visible. In the absence of a visit to at least one of these points, B or C, or a precise knowledge of a bearing, it is not possible to fix absolutely the station, say A, of the traverse. Nevertheless, the fact remains that if the angle subtended by the fixed points is measured and found to be α, say, the station A must lie on an arc of a circle through BC “capable of” this angle α. Is there any assumption which is justifiable under these circumstances?     

自动全站仪的棱镜光斑图像识别算法研究

自动全站仪发射一束红外光,经棱镜反射返回全站仪,由全站仪内置相机采集回光图像,通过获取回光光斑中心的图像坐标,求解全站仪照准棱镜时的偏移值,依据偏移值驱动全站仪自动瞄准棱镜目标。棱镜回光光斑的自动识别与中心定位是实现自动全站仪精确瞄准目标的关键技术之一。提出一种棱镜回光光斑图像的自动识别与中心定位算法,分析了光斑图像的亮度、边界形状等特征,设计了光斑识别与中心定位算法。实验结果表明,所提出的算法准确、有效。     

测量机器人系统构成与精度研究

对测量机器人的特点进行了详细分析 ,对其自动化的工作原理进行了研究 ,其核心技术是用CCD摄像机获取目标图像 ,用计算机软件对数字图像进行分析和匹配 ,提取所需要的特征点 ,再配以精密马达伺服机构控制经纬仪系统的水平和垂直旋转 ,从而实现观测自动化。同时还简要介绍了与测量机器人配套使用的软件 ,并给出了试验结果。     

THE IDEAL DISTANCE FOR PRECISE LEVELLING

Abstract

In order to minimize errors in Precise Levelling it is usual to stipulate a maximum distance at which a staff shall be held from the instrument. The determination of such a distance must result from a compromise between the demands of accuracy and economy, and this distance must of course fall between the lower limit, when because of nearness the instrument cannot be focussed on the staff, and the upper limit, above which the staff cannot be read distinctly.     

遥感数据的分形测量

用分形几何学方法对遥感数据进行了分析,从而定量解释遥感影像。共编制了３种分数维测量方法,它们是分线方法（或等值线方法）,方差方法和三角棱柱方法。用分线方法计算了腾冲地区陆地卫星ＴＭ数据的分数维。图像数据的等值线长度分别按行,按列和按行－列方法处理记取以便能发现图像的模式变化。当图像有明显的走向模式时,按行方法所测量的Ｄ值与按列方法测得的Ｄ值是不同的。按行－列方法测量的Ｄ值几乎不受定向模式的影响。当Ｒ（相关系数）＞０．９时,按３种方式记取等值线所得到的Ｄ值的变化趋势是一致的,都能给出图像数据中的空间相互关系。通过分维测量,不但能描述图像数据的整体特征而且能描述图像数据中的每个值的特征,揭示遥感数据表观的无序性和内在的规律性,更重要的是可把这些Ｄ值与地面物体之间建立联系来探讨各种自然现象中的有用信息。     

THE YEARS 1935–6 AND 1936–7 IN THE GOLD COAST

Abstract

THE Gold Coast can now be said to have recovered from the slump which caused such disastrous consequences in 1931–2 and resulted in a heavy reduction in the establishment of the Survey Department. So far there has been no increase in staff, but more badly needed money for buying stores and increasing the labour staff has been available, and authority has now been given for an increase of 12 in the establishment of African Surveyors; this will result in the re-opening of the Survey School in 1937.     

Detecting repetitive structures on building footprints for the purposes of 3D modeling and reconstruction

ABSTRACT

Repetitive structures of a building share features in terms of geometries and appearance and, therefore, the 3D information for these structures can be transferred from one specification to another for the purpose of 3D modeling and reconstruction once they are identified as repetitive structures. In this paper, a novel approach is proposed for the detection of the repetitive structures specified by the polygons of a building’s footprints. Instead of directly operating on the polygon in 2D space, the polygon is converted into a bend angle function representation in 1D space, whereby an extrusion is represented as a closed polygon intersected by the x-axis and located above it, while an intrusion is represented as a closed polygon below the x-axis. In this way, a polygon of a footprint is decomposed into a number of extrusions and intrusions which can in turn be processed. The task of detecting any repetitive structures specified in a building’s footprints then becomes the task of clustering the intersected polygons in the bend angle function space. The extrusions/intrusions which can be placed in the same clusters can be regarded as repetitive structures. Experiments show that this proposed approach can detect repetitive structures with different sizes, orientations and complexities.     

线阵推扫式相机高精度在轨几何标定

基于偏置矩阵和探元指向角构建了线阵推扫式相机的在轨几何标定模型,并给出了相应的参数求解方法。分析了线阵推扫式相机物理内参数模型与指向角内参数模型的区别与联系,对物理模型到指向角模型的演化过程进行了推导,分析了偏视场相机与正视场相机在使用指向角模型时的不同,并分别给出了两者的具体计算公式。利用嵩山检校场高精度控制数据和天绘一号高分影像验证了本文的模型和解法。实验结果表明,本文的标定模型和求解方法可解算出稳健可靠的内参数;两次标定结果相比,95%的样本探元沿轨方向的指向差异小于0.1像元,93%的样本探元垂轨方向的指向差异小于0.2像元。经在轨几何标定,影像定位精度显著提升。     

THE ADJUSTMENT OFA BLOCK OF AERIAL TRIANGULATION EVALUATED WITH THE WILD A5

Abstract

The procedure for aerotriangulation on the Wild A5 and similar plotting instruments is well known. The first overlap is set up in absolute orientation on well spaced plan and height control and successive overlaps are set up relatively, each to the previous overlap, by eliminating want of correspondence and preserving the height agreement of points falling in the common portion of successive overlaps. When each overlap is correctly set, the co-ordinates of selected points are measured on the instrument (machine co-ordinates). These co-ordinates differ from true ground co-ordinates only in origin, azimuth and scale, provided the settings and measurements are precisely done on error-free models, precisely connected together. However, such ideal conditions are never obtained, and the errors in azimp.th, scale and height datum increase with the number of overlaps added along a strip.     

OBSERVING POLARIS IN DAYLIGHT

Abstract

For azimuth and latitude it is a great advantage to observe Polaris in daylight as it eliminates torches and lamps. The following describes a rule of thumb method of finding the hour angle and a diagram to find the, altitude from the R.A. The altitude is then set on the vertical circle and, by moving the telescope a few degrees about the meridian (by compass), Polaris can easily be spotted near the centre of the field. The telescope must be focussed at infinity. After finding the star, the rigorous observations must be carriéd out.     

场分立体显示系统的硬件实现

根据双摄像机的几何模型,提出了一套双眼立体显示系统的设计方案——场分立体视觉系统。硬件采用流行的ＰＣＩ总线与计算机相连,能够实时获取２个摄像机图像,并能按双眼成像要求的频率工作,产生一个增强的三维世界。     

用激光点光源干涉法检测棱镜的角度误差

用激光点光源干涉法可以有效地检测光学平板的平行差，精度极高。本文详细讨论了如何将这一方法用于检测棱镜角度误差     

Estimation and improvement in the geolocation accuracy of rational polynomial coefficients with minimum GCPs using KOMPSAT-3A

ABSTRACT

In this paper, we propose a method to regenerate Rational Polynomial Coefficients (RPCs) using KOMPSAT-3A imagery and to reduce the geolocation error using minimum ground control points (GCPs). To estimate the new RPCs, the physical sensor model fitted to KOMPSAT-3A imagery was utilized and virtual GCPs over the study area were created. The size of the virtual grid used was 20x20x20. To remove the sensor-related errors in physical sensor model, three different image correction models (image coordinate translation model, shift and drift model, and affine transformation model) were additionally applied. We evaluated our proposed method in two areas within Korea, one in urban (Seoul) and one in rural (Goheung) areas. The results showed that there was a significant improvement after applying the suggested approach in the two areas. The image coordinate translation model is suggested in terms of GCP requirement and expected errors estimated from the error propagation analysis using Gauss–Markov Model (GMM).     

Satellite image analysis using crowdsourcing data for collaborative mapping: current and opportunities

ABSTRACT

Researchers are continually finding new applications of satellite images because of the growing number of high-resolution images with wide spatial coverage. However, the cost of these images is sometimes high, and their temporal resolution is relatively coarse. Crowdsourcing is an increasingly common source of data that takes advantage of local stakeholder knowledge and that provides a higher frequency of data. The complementarity of these two data sources suggests there is great potential for mutually beneficial integration. Unfortunately, there are still important gaps in crowdsourced satellite image analysis by means of crowdsourcing in areas such as land cover classification and emergency management. In this paper, we summarize recent efforts, and discuss the challenges and prospects of satellite image analysis for geospatial applications using crowdsourcing. Crowdsourcing can be used to improve satellite image analysis and satellite images can be used to organize crowdsourced efforts for collaborative mapping.     

‘Video Strip Mapping (VSM)’ for Time‐sequential Monitoring of Revegetation of a Pipeline Route

Abstract

A frequent requirement in post‐construction management of a land pipeline route is to detect revegetation status on a time-sequential basis (usually 5‐10 years). The principal advantage of video is the capacity to provide, in a cost‐effective manner, information required for such a very narrow and long strip target utilising the narrow view angle and dynamic stereo coverage. This paper reports that a video strip monitoring technique requiring solely end lap has been specifically developed with focus on such a narrow and long strip target (e.g. 20‐30m wide and several hundred km long). Such large‐scale video systems are often discussed as being inadequate for a change‐detection application due to geometric and radiometric calibration problems. In spite of such limitations, changes of major thematic land cover classes, particularly for the rapidly recovered target of a pipeline corridor, could be detected successfully by visual or quantitative methods and through further ‘patch dynamics’ analysis in a GIS environment. The results of this study indicate that such calibration problems are generally not a major drawback in acquiring change‐detection information in a practical operational application which requires mostly generalized thematic mapping of relatively simple classes. The results also indicate that Video Strip Mapping (VSM) could be extensively used for other examples of linear thematic mapping.     

Radar Polarization Orientation Shifts in Built-Up Areas

Polarization orientation angle shifts can be seen not only in rugged terrain areas but also in urban areas. The latter is explained by backscatter from a wall of a building or house, which is equivalent to a tilted ground-surface patch. From the scattering model of built-up areas, the polarization orientation angle shift in the built-up areas is given as , where is the wall or street orientation angle, and is the radar incidence angle. Japan Aerospace Exploration Agency Pi-SAR L-band polarimetric data of Gifu, Japan, show a good agreement with the theory. The phase difference between VH and HH polarizations is used to demonstrate the contribution of double-bounce scattering ground-wall and wall-ground over a wide range of wall orientation angles.     

PRACTICAL SAG CORRECTION IN CATENARY TAPING

Abstract

When a line is being measured with a steel tape suspended in catenary but standardized on the flat, the correction for sag is usually computed from the weight of the tape. It can, of course, be determined by actual measurements on the ground, if these are made both on the flat and in catenary, but this is not usually done as it is a tedious process in the absence of a proper standardizing base.     

AAC算法的大气校正复合改进算法

利用模拟数据,评价Autonomous Atmospheric Compensation(AAC)算法的抗噪性,认为AAC算法的抗噪性较弱。基于TASI实测数据,利用AAC算法开展反演计算时,计算结果呈现出多样性问题。结合In-scene Atmospheric Compensation(ISAC)算法中黑体像元的标定方法,提出了一种复合改进算法。首先,利用ISAC算法反演的大气透过率和路径辐射,重新计算AAC算法中大气透过率之比(Tr)和相邻两强弱吸收通道的路径辐射之差(Pd),再次,运用经验公式获得稳定的大气反演结果(大气透过率和路径辐射),有效解决了计算结果多样性的问题。利用复合改进算法,开展的温度与发射率分离实验,证明反演得到的发射率波谱更接近野外实测波谱。