INSTRUCTIONS FOR THE USE OF THE PRISMATIC ASTROLABE AND PROGRAMME FINDER

Abstract

The problem of finding the latitude and longitude of various points on the surface of the earth is one which has been studied for hundreds of years.     

Terrain radiometric calibration of airborne UAVSAR for forested area

In the field of biomass estimation, terrain radiometric calibration of airborne polarimetric SAR data for forested areas is an urgent problem. Illuminated area correction of σ -naught could not completely remove terrain features. Inspired by Small and Shimada, this paper tested gamma-naught on one mountainous forested area using airborne Uninhabited Aerial Vehicle Synthetic Aperture Radar data and found it could remove most terrain features. However, a systematic increasing trend from far range to near range is found in airborne SAR cases. This paper made an attempt to use the relationship between distance to SAR sensor and γ-naught to calibrate γ -naught. Two quantitative evaluation methods are proposed. Experimental results demonstrate that variation of γ -naught can be constrained to a limited extent from near range to far range. Since this method is based on ground range images, it avoids complicated orthorectification.     

Digital Map Generalization at the Age of Enlightenment: a Review of the First Forty Years

Abstract

From 1966 to 2006, digital map generalization has undergone a 40-year development. This paper provides an examination of the development in the first 40 years and an outlook. Emphasis is on theoretical and technical developments.     

THE STEREOGRAPHIC SOLUTION OF THE SPHERICAL TRIANGLE

Abstract

The Stereographic Projection, owing to the ease and accuracy with which it can be drawn on a small scale, offers natural attractiveness for the treatment of spherical geometry upon a plane surface. It would therefore be rash for a present-day writer to claim as novel what may well be an infringement of patent rights morally belonging to Hipparchus, who possibly knew most of what is worth knowing about the matter 2,000 years ago. However, since a fairly extensive delving into writings upon the subject has not brought to light anything quite on the lines here put forward, it may be worth while to systematize in this paper some processes which the present writer has found practically useful for some time past.     

A Dealer's Perspective on the Future of Paper Maps

Abstract

The paper discusses changes that have occurred over the last 15 years in how maps are sold, where they are sold and who is buying them. The emphasis is on the situation in the United States of America, but developments in Europe and the United Kingdom are also included.     

CLAUDE REIGNIER CONDER (1848–1910) AND THE SURVEY OF PALESTINE

Abstract

Few surveyors can have been set a more interesting task than that which fell to the lot of Claude Conder, who first thoroughly explored and mapped the Holy Land some seventy years ago. His work is still of value, and must be referred to by all who are concerned with the ancient topography and archreology of that country. It may be found interesting to consider exactly what the task was, how it was accomplished, and something of the career of the young man who successfully carried it through.     

Fehlertheoretische Maxwell-Boltzmann-Verteilung

Summary The probability to find an error vector in multiples of the Helmert-Maxwell-Boltzmann point error σ² δ_ij(δ_ij Kronecker symbol) is calculated. It is found that the probability is for σ39%, for2 σ86% and for3 σ99% in two dimensions, for σ20%, for2 σ74% and for3 σ97% in three dimensions. The fundamental Maxwell-Boltzmann-distribution is tabulated0,02 (0,02) 4,50.      

The geopotential to (14, 14) from a combination of satellite and gravimetric data

A set of2261 5°×5° mean anomalies were used alone and with satellite determined harmonic coefficients of the Smithsonian' Institution to determine the geopotential expansion to various degrees. The basic adjustment was carried out by comparing a terrestrial anomaly to an anomaly determined from an assumed set of coefficients. The (14, 14) solution was found to agree within ±3 m of a detailed geoid in the United States computed using1°×1° anomalies for an inner area and satellite determined anomalies in an outer area. Additional comparisons were made to the input anomaly field to consider the accuracy of various harmonic coefficient solutions. A by-product of this investigation was a new γ_E=978.0463 gals in the Potsdam system or978.0326 gals in an absolute system if −13.7 mgals is taken as the Potsdam correction. Combining this value of γ_E withf=1/298.25, KM=3.9860122·10 ²² cm ³ /sec ² , the consistent equatorial radius was found to be6378143 m.     

EXPERIMENTS ON THE GROUP GENERALIZATIONG OF CONTOUR LINES FOR TOPOGRAPHIC MAPS

ABSTRACT

This paper analyzes the advantages and disadvantages of two technical lines for automatic group generalization of contour lines. The author suggests that it is possible to get faster and better generalization results if we simulate the intelligence of human experts in program designing, retrieve geomorphological structural information using the input data of 2-D contour lines and derive and output the generalized 2-D results directly.     

Forest structural diversity characterization in Mediterranean landscapes affected by fires using Airborne Laser Scanning data

ABSTRACT

Forest fires can change forest structure and composition, and low-density Airborne Laser Scanning (ALS) can be a valuable tool for evaluating post-fire vegetation response. The aim of this study is to analyze the structural diversity differences in Mediterranean Pinus halepensis Mill. forests affected by wildfires on different dates from 1986 to 2009. Several types of ALS metrics, such as the Light Detection and Ranging (LiDAR) Height Diversity Index (LHDI), the LiDAR Height Evenness Index (LHEI), and vertical and horizontal continuity of vegetation, as well as topographic metrics, were obtained in raster format from low point density data. In order to map burned and unburned areas, differentiate fire occurrence dates, and distinguish between old and more recent fires, a sample of pixels was previously selected to assess the existence of differences in forest structure using the Kruskal–Wallis test. Then, k-nearest neighbors algorithm (k-NN), support vector machine (SVM) and random forest (RF) classifiers were compared to select the most accurate technique. The results showed that, in more recent fires, around 70% of the laser returns came from grass and shrub layers, yielding low LHDI and LHEI values (0.37–0.65 and 0.28–0.46, respectively). In contrast, the areas burned more than 20 years ago had higher LHDI and LHEI values due to the growth of the shrub and tree strata. The classification of burned and unburned areas yielded an overall accuracy of 89.64% using the RF method. SVM was the best classifier for identifying the structural differences between fires occurring on different dates, with an overall accuracy of 68.79%. Furthermore, SVM yielded an overall accuracy of 75.49% for the classification between old and more recent fires.     

NUMBER ONE HUNDRED

Abstract

Readers will notice that this issue of the Review is numbered 100 and, as it has always been published quarterly, this means that it has now been in existence for 25 years and so celebrates its silver jubilee.     

THE TRANSVERSE MERCATOR PROJECTION: A CRITICAL EXAMINATION

Abstract

In January 1938 the writer decided against holding up for more years some work on the Transverse Mercator Projection (E.S.R., 27, 275). The extension to the spheroid was not then complete, nor is the present paper to be regarded as a logical continuance. It is first proposed to show the results of “transplanting” orthomorphically upon the spheroid a spherical configuration forming a graticule.     

THE GEODETIC EVIDENCE CONCERNING WEGENER'S HYPOTHESIS

Abstract

Twenty years ago there seemed to be many good reasons for supposing that Wegener's hypothesis of Continental Drift was untenable. There seemed to be unsurmountable objections to it from a point of view of a mechanism capable of causing tectonic movements of such magnitude; there was disagreement over the correspondence of the orogenic belts in the areas of the earth which are supposed formerly to have been united, as well as over other major geological factors; there was the gravest discordance between the known palaeontological facts and those demanded by the theory; after examination of the geodetic evidence, at least one distinguished geodesist pronounced that it was insufficient. General opinion to-day has perhaps changed and there now appears to be a marked tendency to recognise the cogency of some of Wegener's general arguments and to pay greater attention to the possibilities which he propounded, because it is becoming increasingly clear that the question of the arrangement and of the stability of the primary structural units of the Earth's surface, during geological time, is one of the fundamental problems of geology, as well as of all the allied subjects of geophysics, geomorphology, geodesy, palaeoclimatology and palaeontology. This is the writer's opinion, for what it is worth, after studying the considerable literature on this important and fascinating subject which has accumulated in the course of the past 30 years, during part of a recent leave spent in “browsing” round the Schools and libraries of Cambridge University.     

THE YEAR 1932 IN NORTHERN RHODESIA

Abstract

In spite of the world depression, the effects of which are now being severely felt in this Territory, the Departmental activities were almost a record in regard to output. Not only were applications for land in excess of previous years, but the issue of deeds, the surveys of farms and plots, the work on mineral areas, and the preparation and issue of maps, plans, and diagrams were well above previous years.     

Post-war Progress in Cartography in the Federal Republic of Germany

Abstract

The author spent six years in Germany as Geographic Attache to the United States Embassy in Bonn. His contacts with the cartographic industry resulted in this appraisal of German cartography. He is now Associate Professor in the Department of Geography, University of Nebraska.     

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.     

CONFERENCING

Abstract

Conferencing has become a habit of late years. We are ordered to some, we go joyfully to others, and, at times, we are inclined to wonder what it is all about.     

A new global TEC model for estimating transionospheric radio wave propagation errors

Space-based navigation and radar systems operating at single frequencies of <10 GHz require ionospheric corrections of the signal delay or range error. Because this ionospheric propagation error is proportional to the total electron content of the ionosphere along the ray path, a user friendly TEC model covering global scale and all levels of solar activity should be helpful in various applications. Since such a model is not available yet, we present an empirical model approach that allows determining global TEC very easily. Although the number of model coefficients and parameters is rather small, the model describes main ionospheric features with good quality. Presented is the empirical approach describing dependencies on local time, geographic/geomagnetic location and solar irradiance and activity. The non-linear approach needs only 12 coefficients and a few empirically fixed parameters for describing the broad spectrum of TEC variation at all levels of solar activity. The model approach is applied on high-quality global TEC data derived by the Center for Orbit Determination in Europe (CODE) at the University of Berne over more than half a solar cycle (1998–2007). The model fits to these input data with a negative bias of 0.3 TECU and a RMS deviation of 7.5 TECU. As other empirical models too, the proposed Global Neustrelitz TEC Model NTCM-GLis climatological, i.e. the model describes the average behaviour under quiet geomagnetic conditions. During severe space weather events the actual TEC data may deviate from the model values considerably by more than 100%. A preliminary comparison with independent data sets as TOPEX/Poseidon altimeter data reveals similar results for NeQuick and NTCM-GL with RMS deviations in the order of 5 and 11 TECU (1 TECU = 10¹⁶ electrons/m²) for low and high-solar activity conditions, respectively. The more extended data base of ionosphere information that accumulates in the coming years will help in further improving the set of coefficients of the model.     

THOUGHTS ON THE RUWANDIZ ROAD

Abstract

THE article on Road-Surveying in the East by Mr. J. N. List in the Empire Survey Review, No.6, 263–74, is well worthy of perusal. From the beginning, with his apt quotation from Kipling, to the end where he compares the text-book ideal of road location with the indifferent compromise amidst difficulties that the British engineer in the East is lucky to be able to achieve, I felt in accord with his observations. Having spent four years on a similar kind of work, I consider that this article well deserves the appreciation of its author's profession.     

RE-MEASUREMENT OF THE OLD 10-FT.LENGTH STANDARDS O1 AND OI1 OF THE ORDNANCE SURVEY,AND SOME NOTES ON THE RELATIVE STABILITY OF CERTAIN STANDARDS OF LENGTH

Abstract

The old 10-ft. length standards of wrought iron, O₁ and OI₁, made for the Ordnance Survey in 1826 and 1856 respectively, are briefly described and some account is given of the purpose for which they were constructed.

Both these 10-ft. standards were measured in terms of the Yard in 1864, and one of them in terms of the Metre in 1906. They have recently been re-measured at the National Physical Laboratory, and it was found that, allowing for the known shortening of the Imperial Standard Yard since 1895, the 10-ft. Ordnance Survey standards have remained unchanged in length during the last 50 years or so. Furthermore, if it is assumed that the Imperial Standard Yard shortened rather more rapidly between 1853 and 1895 than it has since that date, then the 10-ft. standards can be said to have remained substantially unchanged in length for nearly a century.

Additional evidence for the change in the length of the Yard between 1853 and 1895 is provided by the results of measurements made in 1864 on some of the old Toise standards used for geodetic surveys on the Continent, and by some recent measurements made at the N.P.L. of another yard standard contemporary with the Imperial Standard.