SURVEYS FOR TITLE

Abstract

One frequently sees suggestions that all surveys for title purposes should be connected to the geodetic framework. These come most frequently from geodesists, and the utility of a geodetic control for land-titles surveys is sometimes used as an additional argument in favour of the institution of such work in areas not yet subject to accurate control. I think few surveyors will be found in opposition, certainly not the writer.     

THE UNITED STATES COAST AND GEODETIC SURVEY: ITS WORK AND PRODUCTS

Abstract

The United States Coast and Geodetic Survey, an agency devoted to the public service of the United States, has just completed the 50th year in its second century of progress. The activities of the Survey in the fields of engineering, science, and higher mathematics provide facts needed in the planning and execution of many of the activities of the nation; our end-products are indispensable to the day-to-day operations of many lines of business and commerce. Thus this highly technical bureau directly aids the United States Department of Commerce in carrying out the mandate of Congress to promote, foster, and develop the industry and commerce of the United States.     

THE QUANTITY OF A DEGREE IN OUR ENGLISH MEASURES

Abstract

This is a brief account of a contribution to geodetic measurement, less well known than the great surveys of the eighteenth and nineteenth centuries, but a remarkable achievement because it was the work of one man and was done more than three centuries ago.     

NOTES ON THE FIXING OF ASTRONOMICAL POSITIONS

Abstract

Except in the sphere of geodetic surveys, there seems to be a lamentable lack of helpful publications for the field surveyor. Comparative methods and standards of accuracy to be expected according to the type of instrument used are rarely to be found in print, and that is the only excuse for the following critical summary of some observations made during the winter of 1933–4.     

The North American datum of 1983: Project methodology and execution

A new adjustment of the geodetic control networks in North America has been completed, resulting in a new continental datum—the North American Datum of 1983 (NAD 83). The establishment ofNAD 83 was the result of an international project involving the National Geodetic Survey of the United States, the Geodetic Survey of Canada, and the Danish Geodetic Institute (responsible for surveying in Greenland). The geodetic data in Mexico and Central America were collected by the Inter American Geodetic Survey and validated by the Defense Mapping Agency Hydrographic/Topographic Center. The fundamental task ofNAD 83 was a simultaneous least squares adjustment involving 266,436 stations in the United States, Canada, Mexico, and Central America. The networks in Greenland, Hawaii, and the Caribbean islands were connected to the datum through Doppler satellite and Very Long Baseline Interferometry (VLBI) observations. The computations were performed with respect to the ellipsoid of the Geodetic Reference System of 1980. The ellipsoid is positioned in such a way as to be geocentric, and its axes are oriented by the Bureau International de l'Heure Terrestrial System of 1984. The mathematical model for theNAD readjustment was the height-controlled three-dimensional system. The least squares adjustment involved 1,785,772 observations and 928,735 unknowns. The formation and solution of the normal equations were carried out according to the Helmert block method. [Authors' note:This article is a condensation of the final report of the NAD 83 project. The full report (Schwarz,1989) contains a more complete discussion of all the topics.]     

PRACTICAL APPLICATION OF THE LAPLACE LONGITUDE-AZIMUTH RELATION TO CONTROL OF GEODETIC ANOMALIES

Abstract

1. In geodetic work a ‘Laplace Point’ connotes a place where both longitude and azimuth have been observed astronomically. Geodetic surveys emanate from an “origin” O, whose coordinates are derived from astronomical observations: and positions of any other points embraced by the survey can be calculated on the basis of an assumed figure of reference which in practice is a spheroid formed by the revolution of an ellipse about its minor axis. The coordinates (latitude = ?, longitude = λ and azimuth = A) so computed are designated “geodetic”.     

RADAR CONTROLLED AIR SURVEY PHOTOGRAPHIC OPERATIONS IN AFRICA 1946–1952

Abstract

In 1943, the Colonial Research Committee accepted a proposal submitted by the Colonial Survey and Geophysical Committee to the effect that a Central Colonial Survey Organization should be established to undertake geodetic surveys and topographical mapping, publish the work completed, hold the required equipment and maintain the necessary records. In order that such an organization, if approved, could commence to operate as soon as possible after the end of war, a detailed scheme for same was called for by the Colonial Research Committee.     

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.     

RECONNAISSANCE MAPPING FROM TRIMETROGON AIR PHOTOGRAPHS IN THE ANGLO-EGYPTIAN SUDAN

Abstract

Trimetrogon air surveys have been used extensively in the United States and Canada but seem to have had less favour on this side of the Atlantic in spite of the fact that large areas over here were photographed in this way during the last war. The Sudan is a very large country, but not a rich one; and up to the present it has not been able to undertake its own aerial photography. The gift of a very large number of American trimetrogon photographs covering half the country was therefore very welcome, and it seemed worth our while to see what could be done with them in spite of the known disadvantages of this type of photography for anything but small scale mapping. The methods of planimetric mapping from these photographs developed in the United States were expressly designed to be as simple as possible and to be capable of division into a number of easy tasks which could be performed by any educated person after a short course of training. Nevertheless we felt that they could be simplified a great deal more if the problem was approached from a different angle, particularly in view of the very high standard of flying which was apparent in the photographs covering the Sudan.     

FIGURES AND FANCIES

Abstract

I may say at once that this article has nothing to do with either the Gaiety chorus or the “Old Firm”: it is merely a statement of what seem to me the fancies in Dr. de Graaff Hunter's paper “Figures of Reference for the Earth”, E.S.R., No. 8,pp. 73–8. Many readers of the Review will share my gratitude to Dr. Hunter for his lucid presentation of the theory underlying the usual geodetic processes. I disagree with only one of his points, and its implications, but unfortunately that point is fundamental.     

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.     

EARTH CURVATURE AND REFRACTION

Abstract

1. For both geodetic and geophysical reasons it is desirable that a method of determining the curvature of the earth at a large number of points, as well as the heights of these points, should be developed. The fact that these two quantities are intimately related in the process of height determination by reciprocal vertical angles has in general been ignored. The present paper does not profess to provide a complete solution; but rather to set forth the requirements and to make some suggestions towards meeting them; and to stress the need for research in the matter of terrestrial refraction, which is certainly long overdue.     

THE INTERNATIONAL UNION OF GEODESY AND GEOPHYSICS. SIXTH GENERAL ASSEMBLY: EDINBURGH, 1936

Abstract

The International Union of Geodesy and Geophysics held its Sixth General Assembly at Edinburgh in September 1936. This paper is not a formal account of the proceedings at Edinburgh, but is intended to convey an idea of what happens at these Conferences and of the geodetic work being done by the countries adhering to the Union.     

A Place to Howl: A GIS Instructional Module on the Mexican Gray Wolf

Abstract

This paper covers the development of a GIS instructional module centered on the reintroduction of the Mexican Gray Wolf in the Southwest, United States. This module is used in an undergraduate geography course on the United States. The paper also reports on how forty‐one students applied the module in trying to find an appropriate location to reintroduce the wolf.     

New solutions for the geodetic coordinate transformation

 The Cartesian-to-geodetic-coordinate transformation is approached from a new perspective. Existence and uniqueness of geodetic representation are presented, along with a clear geometric picture of the problem and the role of the ellipse evolute. A new solution is found with a Newton-method iteration in the reduced latitude; this solution is proved to work for all points in space. Care is given to error propagation when calculating the geodetic latitude and height. Received: 9 August 2001 / Accepted: 27 March 2002 Acknowledgments. The author would like to thank the Clifford W.␣Tompson scholarship fund, Dr. Brian DeFacio, the University of Missouri College of Arts &Sciences, and the United States Air Force. He also thanks a reviewer for suggesting and providing a prototype MATLAB code. A MATLAB program for the iterative sequence is presented at the end of the paper (Appendix A).     

A statistical filter for geodetic observations

A method for filtering of geodetic observationwhich leaves the final result normally distributed, is presented. Furthermore, it is shown that if you sacrifice100.a% of all the observations you may be (1−β).100% sure that a gross error of the size Δ is rejected. Another and, may be intuitively, more appealing method is presented; the two methods are compared and it is shown why Method 1 should be preferred to Method 2 for geodetic purposes. Finally the two methods are demonstrated in some numerical examples.     

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.     

The use of atmospheric dispersion in optical distance measurement

The development of lasers, new electro-optic light modulation methods, and improved electronic techniques have made possible significant improvements in the range and accuracy of optical distance measurements, thus providing not only improved geodetic tools but also useful techniques for the study of other geophysical, meteorological, and astronomical problems. One of the main limitations, at present, to the accuracy of geodetic measurements is the uncertainty in the average propagation velocity of the radiation due to inhomogeneity of the atmosphere. Accuracies of a few parts in ten million or even better now appear feasible, however, through the use of the dispersion method, in which simultaneous measurements of optical path length at two widely separated wavelengths are used to determine the average refractive index over the path and hence the true geodetic distance. The design of a new instrument based on this method, which utilizes wavelengths of6328 ? and3681 ? and3 GHz polarization modulation of the light, is summarized. Preliminary measurements over a5.3 km path with this instrument have demonstrated a sensitivity of3×10 ⁻⁹ in detecting changes in optical path length for either wavelength using1-second averaging, and a standard deviation of3×10 ⁻⁷ in corrected length. The principal remaining sources of error are summarized, as is progress in other laboratories using the dispersion method or other approaches to the problem of refractivity correction.     

THE GEODETIC SURVEY OF CANADA

Abstract

Shortly after the inception of the Geodetic Survey of Canada in 1905, reconnaissance for primary triangulation was commenced in the Ottawa-Montreal area. About the same time, precise levelliilg operations were begun from a bench mark already established by the United States Coast and Geodetic Survey near the International border at Rouses Point in Quebec.     

GEODETIC BEACONS

Abstract

Mr. Clendinning's article on “Signal Lamps” (E.S.R., vol. ii, pp. 15–18) raises a point of major importance in geodetic triangulation. I entirely agree with him that the sole use of heliographs—heliostats to the purist—is in most parts of the world out of date. I also think, and indeed am prepared to state categorically, that the use of acetylene lamps is out of date and was out of date many years ago. The Americans, who are always worth listening to on the economics of surveys, would not otherwise have replaced all their acetylene gear by electric beacons. The answer, in my experience, and for reasons which I shall endeavour to make clear, is generally, but not necessarily always, to provide both helio and electric lighting; but first I should like to summarize the conditions in which luminous signals should be used at all.