摘要:

Mr. President, Ladies, and Gentlemen: Taking the chair of this symposium on the techniques for direct measurement of distance in space, tradition requires that I should do two things—the first one very pleasant and no mere formality, namely to extend to you my greetings, and those of the whole of Section I of the International Association of Geodesy, under whose auspices this symposium is being held.My second task is to say a few words by way of introduction, and I have to confess that I should find this a great deal less pleasant, because I have no skill in the art of talking for talking's sake, were it not for the fact that this too is no mere formality. Fortunately for me I have something to say which comes from the bottom of my heart, and which expresses my most profound conviction

ISSN:0148-0227    

DOI:10.1029/JZ065i002p00385

年代:1960

数据来源: WILEY

摘要:

In recent years various instruments and techniques have been developed for measuring distances electronically. The accuracy of such measurements depends on the accuracy with which time and the velocity of propagation of radio waves can be determined.The National Bureau of Standards, under the sponsorship of the Air Force Ballistic Missile Division, has been studying the effects of atmospheric turbulence on the performance of radio distance‐ and/or velocity‐measuring systems. Many of the data collected in this study are applicable to the problem of determining the accuracy of radio surveying methods, Longterm variations in the apparent length of a 15.5‐mile path in Hawaii are shown, along with the effects of correcting for the atmospheric refractive index observed at 2 to 5 points along the

ISSN:0148-0227    

DOI:10.1029/JZ065i002p00389

年代:1960

数据来源: WILEY

摘要:

In principle an electro‐optical distance‐measuring device is identical to an apparatus to determine the velocity of light. The velocity of light is determined from the relation of the distance traversed by light and the time it requires to do so. The transit time of the light in the methods described below is equal to the period of a usually sinusoidal modulation of the light, as a result of which the light emanating from the transmitter of the distance‐measuring device has either the same phase as that of the light returning over the distance of measurement or the opposite phase.The modulated light traverses a semitransparent mirror, and a portion of it enters a photocell within the optical system of the transmitter and there gives rise to an alternating current having the same phase as the light emanated. The remaining light crosses the measurement path, at the end of which it is reflected and gives rise to an alternating current in a second photocell in the receiver. The phase of this current generally differs from that of the current in the photocell of the transmitter. For a known velocity of light and a known frequency of modulation a phase meter can be immediately calibrated in distances. If the phase meter can determine only certain phase displacements, for example the angle 0° or 180°, the frequency ought to be varied until this phase angle is a

ISSN:0148-0227    

DOI:10.1029/JZ065i002p00394

年代:1960

数据来源: WILEY

摘要:

The basic principal of the geodetic distance meter called the Geodimeter is to measure the time for light to cover the required distance. Knowing the velocity of light, we get the distance. Before we can measure along the light beam it must be marked in some way. This is done by the aid of the Kerr cell, a glass vessel containing the highly purified fluid nitrobenzene and electrodes for applying a voltage to the fluid.

ISSN:0148-0227    

DOI:10.1029/JZ065i002p00404

年代:1960

数据来源: WILEY

摘要:

The Coast and Geodetic Survey has measured 84 geodetic lines with Geodimeters, models 1 and 2, over a 5‐year period. On the basis of this experience, a routine of field operations has been developed and a manual of operation is being prepared. Maintenance problems have been negligible, and only minor modifications of the instruments have been made. The Coast and Geodetic Survey recommends the Geodimeters (model 1 or 2), for measuring first‐order triangulation base lines, trilateration, and traverse, and for calibrating electronic distance‐measuring equipment such as the Telluro

ISSN:0148-0227    

DOI:10.1029/JZ065i002p00410

年代:1960

数据来源: WILEY

摘要:

The California Division of Highways purchased a model 3 Geodimeter in August 1957; its experience to date consists of 3000 hours of observing time, or well in excess of 15,000 miles of line. The Geodimeter crew is equipped with four‐wheel‐drive vehicles, each with 65‐watt radios, plus several small handset radios for walk‐in reflector stations.The range of this instrument may be limited to distances as short as 1 mile in a dense smoke haze, increasing rapidly with better visibility to an outer limit of 25 to 30 miles in the clear air of higher ele

ISSN:0148-0227    

DOI:10.1029/JZ065i002p00411

年代:1960

数据来源: WILEY

摘要:

In geodesy and surveying accurate determinations of distances are of great importance. During World War II many new principles for electronic distance measuring were invented, and some of them have been applied to geodesy. When the greatest geodetic accuracy is needed, however, the electronic methods have, up till now, not always been successful. One of the main disadvantages of purely electronic methods is that ground reflections affect the final results.

ISSN:0148-0227    

DOI:10.1029/JZ065i002p00412

年代:1960

数据来源: WILEY

摘要:

The Tellurometer system, in the form of Microdistancer equipment for overland measurements, was introduced early in 1957. It may be fairly stated that since that date a new vista has been opened to the surveyor—the use of accurate radio line measurements in the art of surveying. As we all know, this has already had a profound effect upon land survey practices. It is the purpose of this paper to discuss new developments of the system as they may be applied to geodesy or hydrograph

ISSN:0148-0227    

DOI:10.1029/JZ065i002p00418

年代:1960

数据来源: WILEY

摘要:

Australia is a large, comparatively undeveloped country, with a small population, as the following statistics show:Area 2,974,581 square milesCoastline 12,210 milesPopulation 10,000,000Its present state of development finds only a small amount of geodetic survey completed, and such a small population cannot provide much manpower to cope with the task of establishing a geodetic survey. Consequently, all methods of increasing the effectiveness of available staff must be explored.

ISSN:0148-0227    

DOI:10.1029/JZ065i002p00430

年代:1960

数据来源: WILEY

摘要:

The development of instruments and of procedures for distance measurements by means of high‐frequency‐modulated light or by means of electromagnetic waves has made significant progress within the past few years. Since Germany has had but little share in this work and in testing the new geodetic methods of measuring, we wanted to present for the first time practical experience with the Tellurometer measurements reported here, particularly about: (1) fixation of the network by means of pure distance measurement; (2) determination of the possible accuracy for trilateration lines and for the point positions; (3) investigation of influence of meteorological conditions and of ground formation on the measurement of the transit time of electromagnetic waves.The measurements were performed in 14 days in the autumn of 1958. All the lines of the extension network (Fig.1) and a second line of the primary triangulation were measured; the lengths were 8.2 to 56.3 km. To determine changes, if any, of the instrument, one line (base line north‐base line south) was measured at the beginning, in the middle, and at the end of the observations. The complete measurement of the first extension triangle showed no differences between the measurements in opposite directions; hence further return observations were not made, in view of the homogeneous ground conditions in the whole network. On all stations four complete measurements were carried through. It was found that the best observation conditions, and consequently the time requirements, depend primarily on the weather and on the time of day. Overcast, mist, and rain are all favorable; with bright sunlight satisfactory measurements were possible only in the morning and in the late afte

ISSN:0148-0227    

DOI:10.1029/JZ065i002p00436

年代:1960

数据来源: WILEY