FURTHER NOTES ON RANGE-FINDING WITH A THEODOLITE

Abstract

Since writing the article which appeared in E.S.R., no. 36, p. 364, the writer has used this method to obtain thousands of spot heights with differences of elevation varying up to 7,500 feet in a single shot. The results of this experience and the modifications introduced in the method may be of some iilterest.     

THE RANGEFINDER IN TROPICAL TOPOGRAPHICAL SURVEYING

Abstract

In text-books on surveying the rangefinder is usually dismissed in one sentence, which merely remarks on its inaccuracies and places in the category of scientific curios an instrument which should be most valuable to the plane-tabler in certain types of country. It is to combat this effect and to help topographers in their arduous work that these notes have been written. They are written from experience gained on topographical survey, on a scale of 1/125,000, in a tropical dependency where reduction of cost is of primary importance.     

NOTES ON THE USE OF THE SLIDE-RULE IN TOPOGRAPHICAL SURVEYING

Abstract

The Survey in which the following methods were employed was for a final map on a scale of 1/500,000, with contours at a 500-foot Vertical Interval. In order to make use of any available information shown on existing maps, the scale used in different areas in the field was that of existing maps. These scales were 1,000 roods to 1 inch (1 rood = 12.396 English feet), 840 roods to 1 inch (1/125,000), and 1,680 roods to 1 inch (1/250,000).     

RANGE FINDING WITH A THEODOLITE AND SHORT BASE

Abstract

In survey work connected with Seismic (Geophysical) investigations, the nature of the operations is such that provisional points many miles apart have frequently to be located with a minimum of delay. When no map and no triangulation exists, the range finding method about to be described is very useful. The method can also be recomlnended for reconnaissance and exploration surveys. It was used by one of the R.A. Survey Regiments with success during the war. The essentials are a good theodolite and a steel tape.     

TRAVERSING WITH THEODOLITE AND CHAIN

Abstract

As Mr H. F. Rainsford (E.S.R., no. 37, vol. v, July 1940) says, the ordinary accurate survey traverse, through its “ordinariness,” has been neglected in the printed word. The technique—perfected by much practice—has been handed down by word of mouth only from father to son, from surveyor to pupil.     

THEODOLITE TRAVERSING IN TROPICAL AFRICA

Abstract

1. In latter years a good deal has been written in English on precise traversing, both in regard to the field work and also the various methods of computation, whatever system of proj ection is used. A bibliography of publications known to the writer is given at the end of this article. But the ordinary traversing most frequently carried out by surveyors, which might be classed as secondary and tertiary, does not appear to have received the same attention in the printed word.     

EXPERIENCES IN PHOTOGRAPHIC SURVEYING

The author outlines his experiences of photographic surveying, in the early years of the 1930's in the Survey of India, which involved the use of simple graphical methods of plotting.     

THE LEVELLING OF A THEODOLITE

Abstract

A Fully equipped theodolite is provided with plate levels, an alidade level, and a striding level. An instrument not so equipped has no title to be considered a “Universal Instrument”, that is to say, an instrument designed for every kind of both terrestrial and celestial measurement. Without a striding level, for example, nothing beyond relatively rough astronomical measures can be expected in general. Modern instruments, capable of giving considerable refinement in terrestrial measures, are frequently not furnished with a striding level; and it is sometimes assumed, with the tacit approval of the makers, that such instruments are equally capable of giving refined astronomical results. On the older type of instrument a striding level—rarely not supplied—could have been, and sometimes was, extemporized; it seems as if ignorance of astronomy of position has led, at least in part, to the construction of theodolites in such a manner as actually to render such extemporization difficult.     

TESTING A THEODOLITE FOR ACCURACY

Abstract

When a theodolite is used to measure an angle, the result will be subjected to certain instrumental and personal errors which affect the measurement. Such errors may be accidental or systematic. Those of the former type, which follow no law and which may with equal probability occur at any graduation, are more easily eliminated, since, if a very large number of readings is taken, it is probable that the errors will cancel out and that the mean will approximate very closely to the correct figure. Systematic errors are usually due to instrumental defects and rnay be expressed as a function of the reading itself; it is the object of the manufacturer to eliminate these as far as possible, since cancellation by reiteration or by repetition is not to be expected wholly.     

FLOATING MARKS IN HYDROGRAPHIC SURVEYING

Abstract

When the area to be sounded out extends seawards beyond the range of visibility of shore-marks or lies altogether out of sight of land, the hydrographic surveyor has to have recourse to floating marks anchored to the sea-bottom. Up to a few years ago the standard beacon used to form these marks was known as the Egeria beacon. This consisted of two 27-gallon wooden casks placed vertically between two stout planks which were secured to each other by six iron stays. Sufficient room was left between the casks to allow a spar tapering from 6 inches in diameter at its heel to 4 inches at its head to pass through holes cut in the planks. This spar is known as the beacon spar, is about 35 feet long, and is held in place above and below by two iron pins attached to two protecting steel sleeves enclosing it. On its heel is shackled a 1¾-cwt. sinker to make the beacon float upright. It projects from 8 to 10 feet above the upper side of the beacon; to this projection is lashed with three hemp lashings a 38-foot bamboo which carries a 16- by 10-foot calico flag, the height of the mark giving a range of visibility in clear weather of 12 miles from the bridge of a surveying ship. A wire strop is fitted round the beacon with a large eye stopped up the bamboo for hoisting in and out of the ship; a length of chain, secured round the beacon spar above and below the beacon, carries a slip to which the moorings are attached.     

SURVEYING AND MAPPING IN CANADA

Abstract

In a country of the size of Canada, the third largest in the world, comprising more than three and a half million square miles and extending through eighty degrees in longitude and a range of latitude from 42° to the North Pole, there is every variety of topography. There are the characteristic accidented regions of the Maritime Provinces and the lower St. Lawrence, vast treeless areas in the Canadian West, and park lands spreading out northwards to merge eventually into the forests, which again give way to the open northern plains that lie towards the Arctic. There are level fertile expanses, hilly areas, marshes, rocky regions of low relief, and localities that display mountainous scenery rivalling anything that exists in other parts of the world. In some places industry has taken its firm foothold with a consequent density of population. In the agricultural areas the population spreads itself out more thinly.     

极坐标测量变形监测网稳定基准点组的检验

分析了全站仪极坐标测量变形监测网的特点,提出了利用坐标转换修正法进行稳定基准点组的检验方法,实现了变形监测网稳定基准点组的检验。     

测绘工程专业《工程测量学》教学改革探讨

本文提出了测绘工程专业《工程测量学》教学中存在的问题，对该课程教学改革的内容和方法进行了探讨。     

GPS-RTK技术在地籍测量中的应用研究

将RTK技术应用于地籍测量中,分析了RTK在地籍控制测量和碎部测量的可行性,阐述了该技术应用于地籍测量中所遇到的问题并进行了深入研究,提出了相应对策.     

THE PROJECTIVE TRANSFORMATION IN AERIAL SURVEYING

Abstract

The paper describes an algebraic method of forming linear equations, giving the coordinates of points in space in terms of the coordinates of their images on the photographic plates. The coefficients which enter into these linear equations form a matrix of the third order. When stereoscopic or similar methods are used for plotting detail, the elements of this matrix give in a convenient form and with the utmost obtainable accuracy the quantities required for setting the photographs in their correct relation to the map and to one another.

An easy and rapid graphical method of obtaining good approximations to all the solutions of the problem of resection in space is described. A method of refining the solutions is given. When the coordinates of the air station are known with fair accuracy an alternative procedure is described. In the absence of ground control suitable for finding the air station by resection a method of eliminating most of the uncertain quantities is obtained. The indeterminate quantities relate to strip photographs as a whole and not to individual photographs. A method of dealing with the coefficients for the complete strip is described.

In finding air stations by resection, point-coordinates in the photographs must be converted into directional coordinates. In other calculations this transformation is unnecessary.     

THE PROJECTIVE TRANSFORMATION IN AERIAL SURVEYING

Abstract

4.3. Having found s we may proceed to obtain the coordinates of the air station. This is the vertex of a pyramid, the base edges being of lengths a, b, c and the opposite edges measuring u, v, w respectively. Let h be the distance of the vertex from the plane of the base, and suppose d, e₁ e₂, e₃ are respectively twice the areas of the base and of the oblique faces in order.     

论测绘仪器在促进测绘事业发展中的作用

本文主要论述了测绘仪器在促进测绘事业发展中的地位与作用，说明加快发展我国测绘仪器的必要性，同时提出了发展我国测绘仪器的建议。