Determining a Vertical Scale for Graphical Representations of Three-Dimensional Surfaces

Abstract

The selection of a vertical scale in the production of block diagrams or three-dimensional views is a decision which can have a great effect on the map reader's perception of the information presented. Advice available in the cartographic literature is extremely subjective and refers mainly to physical data. In the absence of suitable guidelines for statistical mapping, an experimental technique is presented which utilises the power of automated cartography in determining a scale which can be applied to all types of three-dimensional surfaces.     

Books

Abstract

This is a summary of the problems which are involved in the apparently trivial task of measuring the length of a sinuous line on a map. It represents an extended review of the publication Cartometric Measurements, by H. Kishimoto. It is concerned with three basic problems: (1) the sorts of errors which may result from using different instruments and methods of measurement and how these may be corrected: (2) the sorts of errors which may occur in the map and how these may be corrected: 3) the fundamental problem of what is 'length'. Extensive use is made of East European literature on these subjects.     

Pictorial Navigation Displays

Abstract

A pictorial navigation display for aircraft is described, in which the aircraft's ground position and track are continuously displayed, superimposed on the projected image in colour of a topographical map stored on microfilm. The microphotographic technique developed for preparation of the map films is also described. A navigation display of this type will be incorporated in the prototype Concorde supersonic airliner.     

THE ANTI-SHIMMER LEVEL AND LEVELLING STAFF

Abstract

The object of the instrument and special staves is to enable levelling observations to be carried on in conditions of heat-shimmer which would hinder or prevent work by the ordinary methods. The instrument can, however, be used as an ordinary level in normal conditions. The staves for use with the instrument are marked with main bull's-eyes at intervals of 10 cm. and smaller intermediate bull's-eyes at the half-intervals (5cm. from each main bull's-eye). These intervals can be replaced by English units, if desired, and the reverse faces can also be marked with ordinary graduations for use in clear and steady conditions.     

Change vector analysis for disaster assessment: A case study of Hurricane Andrew

Abstract

Remote sensing is a powerful and accurate means of collecting data for wildlife management, particularly for large areas which are difficult of access and feature delicate ecosystems.

Giant panda habitat in the People's Republic of China was evaluated by visual interpretation of multitemporal LANDSAT MSS images. The resulting map, combined with ground survey data, provides important information upon which management decisions can be planned.

This case study illustrates that remote sensing techniques can make a significant contribution to the management programme for the conservation of a threatened animal species.     

Primitive-based Construction Theory for Diagrams in Thematic Maps

Abstract

To enhance the variety of map symbols and to develop new symbol types, a fundamental understanding of the map symbol construction process is mandatory. Current construction theories focus on diagrams without taking georeferencing or interactivity into account. This paper presents a new methodology for the creation of two-dimensional geometric symbols and diagrams for the application in thematic maps. In this context, 49 diagrams found in cartographic literature were analysed and classified regarding their construction properties. As a result of this research, diagrams can be defined using cartographic primitives which are arranged according to six arrangement principles. Since the variation of the primitive's size according to the data values follows a certain geometric direction, each diagram can be explicitly defined based on the three construction properties 'primitive', 'arrangement principle' and 'data direction'.     

THE GEODIMETER: AN INSTRUMENT FOR THE ACCURATE MEASUREMENT OF DISTANCES BY HIGH-FREQUENCY LIGHT VARIATIONS

Abstract

During the last few years a method of measuring accurately the lengths of lines of moderate length by means of high-frequency variations in the intensity of light emitted by a special transmitter, which promises to have many important applications in triangulation and precise traversing, has been devised by Mr. E. Bergstrand, of the Geographical Survey of Sweden. In principle, the method has certain resemblances to the apparatus invented and used by Fizeau for measuring the velocity of light, Bergstrand's instrument having been designed in the first place for the measurement of the same constant. In Fizeau's apparatus, it will be remembered, a ray of light was directed through the cogs of a revolving toothed wheel towards a distant mirror, and, when the wheel reached a certain angular velocity, the ray reflected from the mirror was intercepted by the cogs, so that an observer stationed on the same side of the wheel as the light source no longer saw the reflection of the light in the mirror. The angular velocity of the wheel being known or observed, the time taken for the cogs to obliterate the reflected image could be calculated, and twice the distance to the mirror divided by this time gave the velocity of light. In the Bergstrand apparatus, which is called the “geodimeter”, light pulses of known frequency and varying intensity are directed to the end station of the line whose distance is required, and, after reflection by a mirror at that station, are received back in a special receiving apparatus alongside the transmitter. Here they are converted into small electric currents, which, when the required distance is a certain function of the wave length of the transmitted and reflected pulses, can be made to give zero deflection on a sensitive galvanometer. In this way, the distance to be measured can be determined in terms of the wave length of the pulses. Experiments so far carried out with this apparatus have been successful up to distances of about 36 kilometres. Even with the latest model, however, as we shall see later, it is necessary to know the approximate distance to within 1½ km.     

THE CONFORMAL TRANSFORMATION OF A NETWORK OF TRIANGULATION

Abstract

In a recent issue of this Review, an example is given of the conformal transformation of a network of triangulation using Newton's interpolation formula with divided differences. While the application of the method appears to be new, attention should be drawn to the fact that Kruger employed Lagrange's interpolation formula in a discussion and extension of the Schols method in a paper which was published in the Zeitschrift für Vermessungswesen in 1896. A reference to this paper was given at the end of the paper, “Adjustment of the Secondary Triangulation of South Africa”, published in a previous issue of the E.S.R. (iv, 30, 480).     

THE KEEPING OF SURVEY RECORDS

Abstract

Although the title of this paper may appear to some to refer to a rather humdrum subject which hardly deserves much serious thought or consideration, it is the writer's experience that the vital necessity for keeping clear records of survey work in a permanent form in which they can easily be referred to at any future time is not always sufficiently appreciated by those whose duties do not involve constant or frequent reference to the records of old work. Accordingly, the following notes and suggestions, which are based on practical experience, may be of service in drawing attention to a matter which is really of great practical importance.     

Preliminary results of the establishment of a marine geodetic point in the Pacific Ocean

In November 1968, a marine geodetic control point was established in the Pacific Ocean at a water depth of6,200 feet. The control point (reference point) consists of three underwater acoustic transponders, two of which are powered with lead-acid batteries and the third with an underwater radioisotope power source “URIPS” with a10- to20- year life expectancy. Four independent measuring techniques (LORAC airborne line-crossing, satellite, ship inertial, and acoustic techniques) were used to measure and determine the coordinates of the control point. Preliminary analysis of the acoustic and airborne data indicates that high accuracies can be achieved in the establishment of geodetic reference points at sea. Geodetic adjustment by the method of variation of coordinates yielded a standard point error of±50 to±66 feet in determining the unknown ship station. The original location of the ship station as determined by shipboard navigation equipment was off by about1,600 feet. Paper previously published in the Proceedings of the Second Marine Geodesy Symposium of the Marine Technology Society.     

THE ADJUSTMENT OF A FIRST-ORDER LEVELLING NETWORK

Abstract

In the E.S.R. January and April numbers of 1955, Vol. xiii, Nos. 95 and 96, Mr. Hsuan-Loh Su described the “Adjustment of a Level Net by Successive Approximations and by Electrical Analogy”. It does not seem to be as generally known as it should be that the rigid least square solution can be greatly simplified by utilizing the electrical analogy and solving by Kirchhoff's method. The method as detailed below has been in use for over 40 years.     

A COMBINED CYLINDRICAL PROJECTION

Abstract

The projection in question is a mean between Mercator's and the Equal-Area Cylindrical Projection which is formed by orthographic projection from the sphere upon the circumscribing cylinder. Both projections are computed on the spherical assumption. Mercator's Projection is, of course, the best known of the orthomorphic group; the Equal-Area Cylindrical Projection is the simplest of the equal-area group. Each projection may be said to represent an extreme case; and the mean between them may perhaps, for some purposes, be a useful compromise.     

A vector and raster graphic mapping tool on micro-computers

Abstract

The rapid development of physically-based hydrological information and modelling systems has necessitated enhanced data entry and display systems. A 'mapping tool' is developed for the manipulation and display of spatial information, which is a cost-efficient, self-contained utility system that is suitable for use on micro-computers. It has the ability to be integrated as part of any modelling or information system. Diverse applications using the 'mapping tool' are briefly described including resource management systems for planners, mass balance studies in urban catchments and data entry systems for physically based models.     

Ability to detect and locate gross errors on DEM matching algorithm

Abstract

Digital elevation model (DEM) matching techniques have been extended to DEM deformation detection by substituting a robust estimator for the least squares estimator, in which terrain changes are treated as gross errors. However, all existing methods only emphasise their deformation detecting ability, and neglect another important aspect: only when the gross error can be detected and located, can this system be useful. This paper employs the gross error judgement matrix as a tool to make an in-depth analysis of this problem. The theoretical analyses and experimental results show that observations in the DEM matching algorithm in real applications have the ability to detect and locate gross errors. Therefore, treating the terrain changes as gross errors is theoretically feasible, allowing real DEM deformations to be detected by employing a surface matching technique.     

Road Maps and Advertising in Britain 1860–1940

Abstract

To the writer's knowledge nothing has been published, at the time of writing, on British maps as a selling medium in the period 1860–1940. The only exception proves the rule: D. G. Hindley's Advertising in Victorian England 1837–1901 (see Sources) mentions Chas Baker's 1887 ABC Guide to London and Large Pocket Map of London (see below), but does not place it in its context. This means that the subject can only be studied through the maps themselves, against a background of society at the time.     

Orienteering mapping and higher education

Abstract

The sport of orienteering relies on good quality accurate mapping which reflects the intricate detail of landscapes which are navigated across, on foot, by enthusiastic and experienced competitors of all ages. As a central component of the sport, therefore, mapping has assumed a prominent role in the thinking behind 'The Forward Plan', a study promoted by the British Orienteering Federation (BOP) and sponsored by the English Sports Council. The mapping component of 'The Forward Plan' suggests that extending awareness of mapping and encouraging technical skills are vital steps. The role of institutes of higher education (universities, polytechnics, colleges) in these areas is examined in this paper. The objective is to determine to what extent tertiary educational establishments can assist, in a non-commercial manner, in increasing production and improving standards of orienteering mapping.     

The British Cartographic Society Annual Report

Abstract

There is hidden within early texts information, which if analysed, can be used to increase our understanding of early cartography. This paper considers the possible relevance of the Venerable Bede's concept of Britannia to cartography, his comprehension of the original data, and, why that may have affected his view of Britannia. The information also provides us with an opportunity to construct an alternative for the lost portion of the Tabula Peutingeriana, at least as it pertains to Britain, and to consider the residual areas.     

THE TRANSVERSE MERCATOR PROJECTION OF THE SPHEROID

Abstract

In January 1940, in a paper entitled “The Transverse Mercator Projection: A Critical Examination” (E.S.R., v, 35, 285), the late Captain G. T. McCaw obtained expressions for the co-ordinates of a point on the Transverse Mercator projection of the spheroid which appeared to cast suspicion on the results originally derived by Gauss. McCaw considered, in fact, that his expressions gave the true measures of the co-ordinates, and that the Gauss method contained some invalidity. He requested readers to report any flaw that might be discovered in his work, but apparently no such flaw had been detected at the time of his death. It can be shown, however, that the invalidities are in McCaw's methods, and there seems no reason for doubting the results derived by the Gauss method.