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?     

确定地理网络中心服务范围的一种算法

地理网络的中心服务范围在实际生活中应用广泛,传统方法一般用等时区或等距区表示。本文给出基于地理网络的中心服务范围的概念,并在邻接结点矩阵的基础上,应用广度优先搜索算法确定一个中心的服务范围。     

基于微机的数字修测系统

本文介绍了一种基于微机的数字修测系统。利用现势性较好的像片和已有的地图，通过扫描仪扫描后，借助计算机实现矢量、栅格数据的叠置，进行地图的修测或地图数据库的更新。     

A FIFTY-YEARS RETROSPECT

Abstract

On returning from India I was posted to the command of a depot company at Chatham, a kind of employment which has the advantage of giving one who has been serving in the East a complete change of ideas. The life was pleasant enough, though the duties were mainly of a routine nature. I was not sorry after a year of this agreeable enough life to be given a further change in the shape of special employment on the West Coast of Africa.     

A FIFTY-YEARS RETROSPECT

Abstract

Early in 1902 I accepted with some misgivings the post of Instructor in Surveying at the School of Military Engineering, Chatham, in succession to Major A. C. MacDonnell. I had hardly joined at Chatham when Sir Thomas Holdich offered me the post of second in command of the Chile-Argentina Boundary Commission. However, my new chief, the Commandant, would not let me go, so I settled down to a few years of very pleasant work at Chatham. The first thing to do was to introduce a correct method of computing the geographical coordinates of the trigonometrical stations of a topographical survey, a matter over which my predecessor had suffered a rebuff. Now, however, the War Office personnel had changed; no opposition arose, and the thing was done.     

A FIFTY-YEARS RETROSPECT

Abstract

The Ordnance Survey after the War.—I might class the four years after the War, during which I remained at the head of the Ordnance Survey, as interesting but troublesome. As is well known, an entirely unreasonable impression was spread about that, now that the War was over, there would be a period of great prosperity, and that we should all live like fighting cocks. Well, things did not work out like that. There was a Select Committee on National Expenditure (1918), and this Committee recommended a lengthening of the period of revision of the large-scale maps of the United Kingdom and a consequent, ultimate, reduction of establishment by 500 men. The Treasury later on insisted on a reduction by 600, including Ireland.     

A geoprivacy manifesto

As location‐enabled technologies are becoming ubiquitous, our location is being shared with an ever‐growing number of external services. Issues revolving around location privacy—or geoprivacy—therefore concern the vast majority of the population, largely without knowing how the underlying technologies work and what can be inferred from an individual's location (especially if recorded over longer periods of time). Research, on the other hand, has largely treated this topic from isolated standpoints, most prominently from the technological and ethical points of view. This article therefore reflects upon the current state of geoprivacy from a broader perspective. It integrates technological, ethical, legal, and educational aspects and clarifies how they interact and shape how we deal with the corresponding technology, both individually and as a society. It does so in the form of a manifesto, consisting of 21 theses that summarize the main arguments made in the article. These theses argue that location information is different from other kinds of personal information and, in combination, show why geoprivacy (and privacy in general) needs to be protected and should not become a mere illusion. The fictional couple of Jane and Tom is used as a running example to illustrate how common it has become to share our location information, and how it can be used—both for good and for worse.     

A FIFTY-YEARS RETROSPECT

Abstract

The International Map of the World.—Officially known as the Carte du Monde au Millionième, this undertaking has the following history. At the International Geographical Congress which was held at Bern in 1891, Professor Dr. Albrecht Penck proposed the construction, by all the nations of the world, of an International Map on the scale of 1 to 1 million. This idea was unanimously approved, and a very sketchy outline was roughed out for its prosecution. Of this outline the chief item that has survived is the size of the sheets, which were to be six degrees in longitude by four in latitude. Well, time passed and nothing much happened. Year after year there were a few murmurs at congresses about the map, and a few, a very few, sheets were printed, some by Section “F” of the British War Office. There was no general organization to look after the prosecution of the map, and there were no adequate regulations for its construction. Generally speaking, the official map-making institutions were out of touch with the scheme, and geographical societies and congresses had no money and no power to carry it out.     

A NEW METHOD FOR THE ADJUSTMENT OF A NETWORK OF TRIANGULATION

Abstract

A problem frequently encountered by surveyors in carrying out a system of triangulation, is the adjustment of a network of lower order triangulation to make it geometrically consistent with an existing triangulation of a higher order. For example, in Fig. 1 it will be assumed that the positions of the stations A, B, and C have already been determined and that it is now required to determine the positions of the stations a, b, c, d, e and f from the measured values of the internal angles of the network of triangulation shown. In practice, several different solutions have been suggested, ranging from rigorous least squares methods to semi-graphical solutions. The method described in this article is believed to be original and may prove of interest to surveyors.     

A FIFTY-YEARS RETROSPECT

Abstract

In 1911 Lord Carrington, then President of the Board of Agriculture and Fisheries, offered me the appointment of Director-General of the Ordnance Survey of the (then) United Kingdom, and I need not say that I accepted the appointment. I took over from my predecessor, Colonel S. C. N. Grant, on the 22nd August. The Ordnance Survey was a single department charged with the mapping, on a great variety of scales, of England and Wales, Scotland, and Ireland. Officers and men were freely interchangeable between the different countries.     

A FIFTY-YEARS RETROSPECT

Abstract

On returning from Central Africa I was posted, for ordinary duty, to Edinburgh, and after a short time I found myself again on the Ordnance Survey. Late in 1899 the South African War broke out, and early in 1900 I was sent out to South Africa in command of a very small Field Survey Section. But before describing the limited activities of this Section it may be as well to give some idea of the attitude of the higher civil and financial authorities towards the proposition that it is desirable to be prepared with maps of possible theatres of war.     

A TRIGONOMETRICAL UPSET

Abstract

If the geographical co-ordinates, Φ₀, L 0, and the azimuth A ₀ at a station O of a triangulation undergo corrections, ?Φ₀, ?L ₀ and ?A ₀, the geographical co-ordinates, Φ, L, and the azimuth A have to be re-computed for all the vertices throughout the whole triangulation. This is a tedious operation. It may be vastly simplified, however, by the employment of differential formulae. The derivation of these formulae would consume considerable space, so that the results alone are given here.     

A RESECTION METHOD

Abstract

This is a variation of the well-known device of successive approximations. It was first used by the writer about 15 years ago on a Seismic (Geophysical) Survey when resections were continually employed to locate Shot Points and Geophonestations set on arcs of 10 to 15 miles radius. Speed was an important factor, and the normal text book methods of resection were very tedious. As far as is known the method is original. It is now used by many surveyors, and the writer trusts it will be of use to others. The method is easy to remember as it has no set formula and does not involve any elaborate geometrical construction.     

DEVELOPMENT OF A LOW-COST MOBILE MAPPING SYSTEM: A SOUTH AMERICAN EXPERIENCE

This paper presents the prototype of a low-cost terrestrial mobile mapping system (MMS) composed of a van, two digital video cameras, two GPS receivers, a notebook computer, and a sound frame synchronisation system. The imaging sensors are mounted as a stereo video camera on top of the vehicle together with the GPS antennae. The GPS receivers and the notebook computer are configured to record data referred to the vehicle position at a planned time interval. This position is subsequently transferred to the road images. This set of equipment and methods provide the opportunity to merge distinct techniques to make topographic maps and also to build georeferenced road image databases. Both vector maps and raster image databases, when integrated appropriately, can give spatial researchers and engineers a new technique whose application may realise better planning and analysis related to the road environment. The experimental results proved that the MMS developed at the São Paulo State University is an effective approach to inspecting road pavements, to map road marks and traffic signs, electric power poles, telephone booths, drain pipes, and many other applications important to people's safety and welfare. A small number of road images have already been captured by the prototype as a consequence of its application in distinct projects. An efficient organisation of those images and the prompt access to them justify the need for building a georeferenced image database. By expanding it, both at the hardware and software levels, it is possible for engineers to analyse the entire road environment on their office computers.     

环境星CCD数据大气校正研究

利用6S模型和同步气象资料,对国产环境与灾害监测预报小卫星HJ-1 A的CCD1传感器数据进行了大气校正和反射率反演。同时对CCD1传感器1～4波段大气校正前后的反射率变化进行了对比研究,发现大气校正后的1～3波段的地面反射率明显降低,4波段的地面反射率升高;利用同步野外实测地面数据对大气校正后的反射率数据进行了检验,两者结果基本一致;此外,还进行了定量化误差分析,以同步野外实测地面数据作为标准,将大气校正后的反射率数据与之对比,分析了可能带来误差的原因。结果表明,利用6S大气校正方法能够有效去除HJ-1 A星CCD图像的大气影响,获取地物绝对反射率。     

A SAR conjugate mirror

A radar transponder was constructed, which modifies the received signal such that its complex conjugate is returned to the radar, qualities of the conjugate mirror used in optics and acoustics. For a monostatic synthetic aperture radar (SAR), a perfect conjugate mirror will reflect a signal back to the radar with no phase shift due to the propagation path. The signal received by the transponder is also decorrelated from other targets, enhancing the transponder signal in the SAR image. This letter describes a transponder operated as a SAR conjugate mirror and an experiment with the European Remote Sensing 1 satellite, demonstrating the feasibility and characteristics. The significance for transponder design is addressed and possible applications discussed.     

A COMBINED PROJECTION

Abstract

The projection in question is a mean between the Cylindrical Equivalent (Equal-Area) Projection and its Transverse Projection. The position of any point on the earth's surface is defined by the mean x and the mean y of the two constituent projections.     

A CASE OF COUNTERSECTION

Abstract

Countersection is a jointure of intersection and resection. In addition to the elementary problem of a single triangle, whereof one angle is intersecting and one resecting—sometimes known as the problem of “lining in”—, there are many others of a nature somewhat more complex.