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.     

Generalization of the Lambert–Lagrange projection

The Lagrange projection represents conformally the terrestrial globe within a circle. This is achieved by compressing the latitude and longitude and by applying the new coordinates into the equatorial stereographic projection. The same concept can be generalized to any conformal projection, although the application of this technique to other analytical functions is less known. In this work, the general Lambert–Lagrange projection formula is proposed and the application of the modified coordinates is discussed on projections: stereographic, conformal conic and Gauss–Schreiber. In general, the results are merely a curiosity, except for the case of Gauss–Schreiber, where the use of coordinates with altered scale can be applied in the optimization of conformal projections.     

Hodges–Lehmann estimates in deformation analyses

This paper presents new variants of the Hodges–Lehmann estimates, which belong to the class of $R$ -estimates. The new approach to this method arises from the need of taking into account differences in accuracy of geodetic measurements, which is not possible while applying traditional $R$ -estimates. The theoretical assumptions of the conventional Hodges–Lehmann estimates are supplemented with the information about the accuracy of observations and two new variants of the estimates in question are derived by applying the principles proposed by Hodges and Lehmann, hence they are called the Hodges–Lehmann weighted estimate. The main properties of the new estimates follow from such approach, and from the practical point of view, the most important seems to be their robustness against outliers. Since the first estimate proposed is a natural estimator of the shift between two samples, it can be applied in deformation analysis to estimate point displacements. The paper presents two numerical examples that show the properties as well as possible applications of the new estimates.     

CANADIAN SHORAN EFFORT, 1949–1953

Abstract

The application, in Oanada, of shoran electronic length measurement to surveying and mapping may be regarded as having been initiated in 1947, when experimental work by Federal Government bureaus was conducted in the vicinity of Ottawa over several long lines between stations of the first-order triangulation. During the succeeding two winters this work was continued, and the results indicated shoran as suitable for establishing position, in Canada's vast northland, quickly and with greater accuracy than by means of astronomic methods. It was realized that trilateration might fail in securing the necessary accuracy because of the many factors involved. Since no information was available, or even existed, from the experience of other survey organizations as to the error in position which might be generated in a comparatively long arc, the first work planned was for a 1100-mile axial-length arc between geodetic bases. This arc, situated in Manitoba and Saskatchewan, was measured in 1949 and 1950. The result indicated that shoran, with careful supervision of all details, could produce results of accuracy superior to astronomic positioning, which is the only reasonable and speedy alternative method of control for mapping at the present stage of development of the northern areas.     

CANADIAN SHORAN EFFORT, 1949–1953

Abstract

In order to reduce the shoran distance to geodetic distance, it is necessary to know the following: (a) the height above sea level of the ground stations, (b) the elevation of the airborne station at the time of transits and (c) the path and velocity of the radar wave through the atmosphere.     

SensePlace3: a geovisual framework to analyze place–time–attribute information in social media

SensePlace3 (SP3) is a geovisual analytics framework and web application that supports overview + detail analysis of social media, focusing on extracting meaningful information from the Twitterverse. SP3 leverages social media related to crisis events. It differs from most existing systems by enabling an analyst to obtain place-relevant information from tweets that have implicit as well as explicit geography. Specifically, SP3 includes not just the ability to utilize the explicit geography of geolocated tweets but also analyze implicit geography by recognizing and geolocating references in both tweet text, which indicates locations tweeted about, and in Twitter profiles, which indicates locations affiliated with users. Key features of SP3 reported here include flexible search and filtering capabilities to support information foraging; an ingest, processing, and indexing pipeline that produces near real-time access for big streaming data; and a novel strategy for implementing a web-based multi-view visual interface with dynamic linking of entities across views. The SP3 system architecture was designed to support crisis management applications, but its design flexibility makes it easily adaptable to other domains. We also report on a user study that provided input to SP3 interface design and suggests next steps for effective spatiotemporal analytics using social media sources.     

THE PERU-BOLIVIA BOUNDARY COMMISSION 1911–13

Abstract

That Peru should have drawn from the British Army the technical personnel for the survey in connexion with her boundary demarcation with Bolivia is interesting, because at this period she employed missions of French officers both for her army and for her navy. Her neighbours—certainly Chile and Bolivia—looked to Germany for instruction in military matters. Militarily England has had little connexion with Peru's development. The fact that between the capital Lima and its port Callao there stands a statue to an Englishman, a general, whose memoirs are to be found in the War Office library and who fought to win the independence of Peru from Spain, can hardly have been sufficient reason for the selection of British military officers to do her boundary work. The effectiveness of the work of Colonel Sir Thomas Holdich on the Chile-Argentina frontier was certainly a leading reason for this choice; but it is probable that the excellent work in survey and exploration accomplished for Bolivia by Lieut.-Colonel P. H. Fawcett, R.A., was the ultimate factor which decided Peru to seek in the British Army an officer of equal rank with him to serve her interests in the cause of frontier demarcation, while Fawcett was serving those of Bolivia. Fawcett's most outstanding piece of exploration had been done on this frontier a year or two before the boundary commissions assembled, and this was his ascent of the Heath river from mouth to source. During this ascent he sowed the seeds of friendship with the.natives of this river, although he was assailed by them with a flight of arrows when struggling up the river with his canoes.     

A three-dimensional network-based space–time prism

Time-geographic concepts are effective tools for the geovisualization of human activity patterns and to assess individual accessibility. In their traditional form, however, time-geographic concepts assume uniform travel velocities in an isotropic and homogeneous space. Because transportation systems confine travellers to links of road and rail networks with time-varying flows, these premises are typically unsatisfied in real-world situations. This paper provides an innovative approach to ameliorate the realism and applicability of space–time prisms by developing new three-dimensional space–time objects. Three-dimensional solid models which account for non-uniform movement are discussed, and their usefulness is assessed and illustrated by means of an example.      

Delineation and classification of rural–urban fringe using geospatial technique and onboard DMSP–Operational Linescan System

This study aims to analyse the processes and patterns of peri-urbanization using diurnal earth observation data-sets from onboard DMSP–Operational Linescan System. In this study, multiple correlation, simple and conditional linear regression are used to find out the degree of relationship and spatial behavioural pattern of the factors responsible for the urbanization. All the factors are standardized using the Analytical Hierarchy Process (AHP) coupled fuzzy membership functions. AHP is used to derive the weighting of the factors to produce the urbanity index. In total three functional zones – urban, rural and urban shadow are generated based on factor standardization and spatial contiguity index. Urban fringe is sharing ≥ 60% of Urbanity Index followed by rural fringe (39.50–60% of urbanity index) and urban shadow <39.50% of urbanity index. Shape index indicates that the city is going through unplanned development following cross to star shape growth.     

A sun–crown–sensor model and adapted C-correction logic for topographic correction of high resolution forest imagery

Canopy shadowing mediated by topography is an important source of radiometric distortion on remote sensing images of rugged terrain. Topographic correction based on the sun–canopy–sensor (SCS) model significantly improved over those based on the sun–terrain–sensor (STS) model for surfaces with high forest canopy cover, because the SCS model considers and preserves the geotropic nature of trees. The SCS model accounts for sub-pixel canopy shadowing effects and normalizes the sunlit canopy area within a pixel. However, it does not account for mutual shadowing between neighboring pixels. Pixel-to-pixel shadowing is especially apparent for fine resolution satellite images in which individual tree crowns are resolved. This paper proposes a new topographic correction model: the sun–crown–sensor (SCnS) model based on high-resolution satellite imagery (IKONOS) and high-precision LiDAR digital elevation model. An improvement on the C-correction logic with a radiance partitioning method to address the effects of diffuse irradiance is also introduced (SCnS + C). In addition, we incorporate a weighting variable, based on pixel shadow fraction, on the direct and diffuse radiance portions to enhance the retrieval of at-sensor radiance and reflectance of highly shadowed tree pixels and form another variety of SCnS model (SCnS + W). Model evaluation with IKONOS test data showed that the new SCnS model outperformed the STS and SCS models in quantifying the correlation between terrain-regulated illumination factor and at-sensor radiance. Our adapted C-correction logic based on the sun–crown–sensor geometry and radiance partitioning better represented the general additive effects of diffuse radiation than C parameters derived from the STS or SCS models. The weighting factor W_t also significantly enhanced correction results by reducing within-class standard deviation and balancing the mean pixel radiance between sunlit and shaded slopes. We analyzed these improvements with model comparison on the red and near infrared bands. The advantages of SCnS + C and SCnS + W on both bands are expected to facilitate forest classification and change detection applications.     

Altimetry–gravimetry problems with free vertical datum

 The definition and connection of vertical datums in geodetic height networks is a fundamental problem in geodesy. Today, the standard approach to solve it is based on the joint processing of terrestrial and satellite geodetic data. It is generalized to cases where the coverage with terrestrial data may change from region to region, typically across coastlines. The principal difficulty is that such problems, so-called altimetry–gravimetry boundary-value problems (AGPs), do not admit analytical solutions such as Stokes' integral. A numerical solution strategy for the free-datum problem is presented. Analysis of AGPs in spherical and constant radius approximation shows that two of them are mathematically well-posed problems, while the classical AGP-I may be ill posed in special situations. Received: 2 December 1998 / Accepted: 30 November 1999     

THE ORTHOMORPHIC PROJECTION OF THE SPHEROID–III

Abstract

In the last instalment we were able to obtain most of the surveyor's projections in common use by applying simple scale conditions to the meridians and parallels. This method of approach naturally suggests that results of some value might be obtained by applying similar conditions to the plane co-ordinate lines. If we do so, we are immediately led to consider curves on the surface known as geodesics, which are the nearest approach to straight lines it is possible to draw on a curved surface. Accordingly, we give some account of these curves for the benefit of surveyors who have not hitherto made their acquaintance.     

Cartographic Design and the Space–Time Cube

This paper reports on the results of an empirical evaluation that aimed to define the effectiveness and efficiency of different visual variables in depicting the Space–Time Cube’s (STC) content. Existing STC applications demonstrate that the most used visual variables are size and colour hue. Less is known, however, about their usability metrics. The research sets design criteria for STC contents, such as space–time paths, based on the cartographic design theory. The visual variables colour hue, colour value, colour saturation, size and orientation have been applied in two different use case studies. Besides, to support the three-dimensional visual environment, depth cues such as shading and transparency were considered too. User tests have been executed based on real-world problems with particular attention for the visualization strategy and data complexity. The outcomes revealed the most efficient and effective visual variables to represent data of various complexities in the STC.     

SARAWAK TRIANGULATION REPORT. SEASON 1932–3

Abstract

The first part of the season (November–January) being spent on urgent reconnaissance of both the primary chain and secondary series in the Samarahan, Sadong, and Simanggang Districts, it was not until loth February that observing was begun. The programme called for two observers, one occupying primary stations and one occupying the secondary points, the secondary rays from primary stations being observed at one occupation of the point.     

On the geoid–quasigeoid separation in mountain areas

The separation between the reference surfaces for orthometric heights and normal heights—the geoid and the quasigeoid—is typically in the order of a few decimeters but can reach nearly 3 m in extreme cases. The knowledge of the geoid–quasigeoid separation with centimeter accuracy or better, is essential for the realization of national and international height reference frames, and for precision height determination in geodetic engineering. The largest contribution to the geoid–quasigeoid separation is due to the distribution of topographic masses. We develop a compact formulation for the rigorous treatment of topographic masses and apply it to determine the geoid–quasigeoid separation for two test areas in the Alps with very rough topography, using a very fine grid resolution of 100 m. The magnitude of the geoid–quasigeoid separation and its accuracy, its slopes, roughness, and correlation with height are analyzed. Results show that rigorous treatment of topographic masses leads to a rather small geoid–quasigeoid separation—only 30 cm at the highest summit—while results based on approximations are often larger by several decimeters. The accuracy of the topographic contribution to the geoid–quasigeoid separation is estimated to be 2–3 cm for areas with extreme topography. Analysis of roughness of the geoid–quasigeoid separation shows that a resolution of the modeling grid of 200 m or less is required to achieve these accuracies. Gravity and the vertical gravity gradient inside of topographic masses and the mean gravity along the plumbline are modeled which are important intermediate quantities for the determination of the geoid–quasigeoid separation. We conclude that a consistent determination of the geoid and quasigeoid height reference surfaces within an accuracy of few centimeters is feasible even for areas with extreme topography, and that the concepts of orthometric height and normal height can be consistently realized and used within this level of accuracy.     

Time geography in a hybrid physical–virtual world

Journal of Geographical Systems - Time geography was conceptualized in the 1960s when the technology was very different from what we have today. Conventional time-geographic concepts therefore were...     

Adaptive Relative Motion Representation of Space–Time Trajectories

Abstract

In this article the author explains how military geography information is being exploited by modern Armed Forces. In doing so he highlights some of the underlying principles of surveying and cartographic that define paper mapping, and that are still applicable in the digital era.

This article reflects the personal views of Lieutenant Colonel Prain who is currently serving in the Headquarters of the Defence Geographic and Imagery Intelligence Agency.