Triangulation was used by ancient Egyptians, Greeks, and other peoples at a very early date, with crude sighting devices that were improved into the diopter (an early theodolite) in the 1st century AD by Hero of Alexandria.
Notes:
alignment – выравнивание, расположение; diopter – диоптр; sighting – визирование; AD – нашей эры; adjacent – смежный.
UNIT 4
HISTORY OF SURVEYING
It is quite probable that surveying had its origin in ancient Egypt. The Great Pyramid at Giza was built in 2700 BC. Its nearly perfect squareness affirm the ancient Egyptians’ command of surveying.
Evidence of some form of boundary surveying as early as 1400 BC has been found in the fertile valleys of Tigris, Euphrates and Nile rivers. Boundary stones marking land plots have been preserved.
There is some evidence that wooden rods were used by the Egyptians for distance measurement. They had the groma which was used to establish right angles.
There is no record of any angle-measuring instruments of that time, but there was a level consisting of a vertical wooden frame with a plumb bob. Thus, with their simple devices, the ancient Egyptians were able to measure land areas, replaced property corners lost when the Nile destroyed the markers during floods, and built the huge pyramids to exact dimensions.
The Greeks used a form of log line for recording the distances run from point to point along the coast while making their slow voyages from the Indus to the Persian Gulf about 325 BC. The magnetic compass was brought to the West by Arab traders in the 12th century AD.
During their occupation of Egypt, the Romans acquired Egyptians’ surveying instruments, which they improved slightly and to which they added the water level and the plane table. The water level consisted of a tube turned upward at the ends and filled with water. At each end there was a sight made of crossed horizontal and vertical slits. It was used to establish the grades of the Roman aqueducts. In laying out their great road system, the Romans are said to have used the plane table. It consists of a drawing board mounted on a tripod and of a straightedge along which lines are drawn. It was the first device capable of recording or establishing angles.
The vernier, an auxiliary permitting more accurate readings, the micrometer microscope, telescopic sights, and spirit levels were all incorporated in theodolites by about 1720. It was one of the greatest advances in surveying methods, as it enabled angle measurements to be made with portable instruments far more accurately than had previously been possible.
By the late 18th century modern surveying can be said to have begun. One of the most notable early feats of surveyors was the measurement in the 1790s of the meridian from Barcelona, Spain, to Dunkirk, France. In addition to modification of existing instruments two revolutionary mapping and surveying changes have been introduced: photogrammetry, or mapping from aerial photographs (about 1920), and electronic distance measurement. Important technological development in surveying in 1970s included the use of satellites as reference points for geodetic surveys and computers to speed the processing and recording of survey data.
Word list
auxiliary | вспомогательное устройство |
readings | показания измерительных приборов |
origin | начало; происхождение |
land plot | |
rod | рейка |
groma | древний геод. инструмент, предшественник теодолита |
plumb bob | отвес |
property | собственность |
marker | знак, метка |
flood | наводнение |
dimension | размер |
log line | лаглинь (корабельный трос, используемый для определения пройденного судном расстояния) |
to lay out | прокладывать; размещать |
plane table | мензула |
sight | визир |
spirit level | спиртовый уровень |
theodolite | теодолит |
tripod | штатив, тренога |
photogrammetry | фотограмметрия |
straightedge | поверочная линейка; линейка кипрегеля |
aerial photograph | аэроснимок |
vernier | верньер |
I Pronounce correctly:
ancient; surveying; Egypt, Egyptians; pyramid; theodolite; photogrammetry; vernier; microscope; aerial; satellite; angle; voyage; aqueduct; square, squareness.
II Find English equivalents of the following:
съемка границ, измерение земли, земельный участок, измерение расстояний, прямой угол, границы частной собственности, вдоль побережья, обработка данных съемки.
III Complete the sentences:
1. Surveying had its origin in … .
2. Egyptians used … for distance measurement.
3. … was brought to the West by the Arabs.
4. Romans used … for laying out roads.
5. Plane table consists of a … mounted on a tripod.
6. The vernier, the microscope and spirit levels were incorporated in … .
IV Answer the questions:
1. Where did surveying take its origin? How can you prove the fact?
2. What instrument did Egyptians use to establish right angles?
3. How did the Greeks record distances?
4. Who invented the magnetic compass?
5. What surveying instrument did the Romans add to those of Egyptians?
6. What was the plane table used for in Rome?
7. When did modern surveying begin?
8. What revolutionary changes in surveying were introduced in 1920s?
V Translate into English:
1. Первое упоминание о съемке относится к Древнему Египту.
2. Для измерения расстояний египтяне использовали деревянные рейки.
3. С помощью простейших инструментов древние египтяне умели измерять расстояние, устанавливать межевые знаки и строить огромные пирамиды.
4. Магнитный компас был изобретен арабами.
5. К инструментам, изобретенным египтянами, римляне добавили водяной уровень и мензулу.
6. В семидесятых годах для геодезической съемки стали применять спутники.
7. Для ускорения обработки данных съемки применяются компьютеры.
UNIT 5
METHODS OF SURVEY
Geodetic surveys involve such extensive areas that allowance must be made for the Earth’s curvature. The basic survey method is triangulation that consists of accurately measuring a base line and computing other locations by angle measurement. Baseline measurements are reduced to sea-level length to start computations, and corrections are made for spherical excess in the angular determinations.
A first requirement for topographic mapping of a given area is an adequate pattern of horizontal and vertical control points, and initial step is the assembly of all such existing information. This consists of descriptions of points for which positions (in terms of latitude and longitude) and elevation above mean sea level have been determined.
The simplest form of horizontal control is the traverse, which consists of a series of marked stations connected my measured courses and the measured angles between them. When such a series of distances and angles returns to its points of beginning, it can be checked.
Establishing the framework. Most surveying frameworks are erected by measuring the angles and the lengths of the sides of a chain of triangles connecting the points fixed by global positioning. The location of ground features are then determined in relation to these triangles by less accurate and therefore cheaper methods.
For centuries the corners of these triangles have been located on hilltops, each visible from at least two others, at which the angles between the lines joining them are measured. This process is called triangulation. The lengths of one or two of these lines, called bases, are measured with great care; all the other lengths are derived by trigonometric calculations from them and the angles. In small flat areas, working at large scales, it may be easier to measure the lengths of all sides rather than the angles between them. This procedure is called trilateration.
EDM has greatly simplified an alternative technique, called traversing, for establishing a framework. In traversing, the surveyor measures a succession of distances and the angles between them, usually along a travelled route or a stream.
Once the framework has been established, the surveyor proceeds to the detail mapping, starting from these ground marks and knowing that their accuracy ensures that the data obtained will fit precisely with similar details obtained elsewhere in the framework.
Word list
allowance | допуск; допускаемое отклонение |
excess | избыток; излишек |
spherical excess | сферический избыток |
in terms of | в терминах; с точки зрения |
rather than | а не; вместо |
trilateration | трилатерация |
traverse | теодолитный ход; полигонометрия |
traversing | пpоложение хода; полигонометрическая съёмка |
baseline | базисная линия, базис |
control | сеть опорных точек, геод. основа; разбивка сети; привязка геодезической сети |
horizontal control | плановое обоснование; сеть плановых опорных точек |
vertical control | высотное обоснование; сеть высотных опорных точек; нивелирная сеть |
distance | расстояние; проложение |
EDM - electronic distance | измерение расстояния с помощью электронных измерительных приборов |
correction | исправление; поправка |
route | маршрут, курс; ход, ходовая линия |
chain of triangles | звено триангуляции |
I Pronounce correctly:
allowance; curve, curved, curvature; triangle, triangulation; trilateration; excess; traverse; determine, determination; compute, computer, computation; sphere, spheroid, spherical; alternative; proceed, procedure; precise, precisely, precision; feature.
II Complete the sentences:
1. The method when baseline and angles are measured and other locations are computed is called … .
2. If it is easier to measure the lengths than angles the procedure of … is used.
3. … is a series of stations connected by measured lines and measured angles between them.
4. In traversing the surveyor measures distances and … between them.
5. … has made establishing framework easier.
III Find English equivalents of the following:
делать поправку; угловые измерения; создание топографической карты; точки планового и высотного обоснования; высота над уровнем моря; углы треугольников; выводить с помощью тригонометрических расчётов; составление подробной карты.
IV Answer the questions:
1. In which cases is the Earth’s curvature taken into account?
2. What is the basic survey method?
3. What is triangulation?
4. What does the traverse consist of?
5. How are most of surveying frameworks erected?
6. What procedure is called trilateration?
V Translate into English:
1. Основным способом съёмки является триангуляция.
2. При угловых измерениях делаются поправки на кривизну Земли.
3. Полигонометрия состоит из ряда станций, расстояния и углы между которыми измерены.
4. Длина базисной линии тщательно измеряется, а все другие расстояния рассчитываются тригонометрически по углам.
5. Если измеряются углы, а стороны рассчитываются тригонометрически, способ называется трилатерацией.
6. Электронные измерительные приборы значительно облегчили процесс полигонометрии.
VI Translate into Russian:
Trilateration
It is a method of surveying in which the lengths of the sides of a triangle are measured, usually by electronic means, and, from this information, angles are computed.
By constructing a series of triangles adjacent to one another, a surveyor can obtain other distances and angles that would not otherwise be measurable. Formerly trilateration was little used in comparison to triangulation, a method of determining two sides and an angle of a triangle from the length of one side and two angles, because of the difficulty of the computations involved. But the development of electronic distance-measuring devices has made trilateration a common and preferred system. Except that only lines are measured, while all angles are computed, the field procedures for trilateration are like those for triangulation.
UNIT 6
SURVEYING INSTRUMENTS
The instrumentation, procedures, and standards involved in making original surveys have improved remarkably in recent years. Geodetic, topographic, hydrographic, and cadastral surveys have been facilitated by the application of electronics and computer sciences. At the same time, superior optics and more refined instruments, in general, have enhanced the precision of observations and accuracies of the end product.
It is surprising that classical instruments are still found in many fields of surveying. Users of optical precision theodolites give the following reasons for that:
1.Classical instruments can be used to perform many new surveying tasks without any difficulties.
2.Good performance at a reasonable price.
3. They are ready for use at any time independent of the battery charge.
4. Even under extreme climatic conditions they function without error.
5. With a distance meter, they can be upgraded to a cost-effective total station.
Though different modern techniques are acceptable for measuring angles usually special instrument called theodolite is used in surveying for this purpose. It can assure the accuracy required in the framework needed for precise mapping. The theodolite consists of a telescope pivoted around horizontal and vertical axes so that it can measure both horizontal and vertical angles. These angles are read from circles graduated in degrees and smaller intervals of 10 or 20 minutes. The exact position of the index mark ( showing the direction of the line of sight) between two of these graduations is measured on both sides of the circle with the aid of a vernier or micrometer. The accuracy in modern first-order geodetic instruments, with five-inch glass circles, is approximately one second of arc, or 1/3.600 of a degree. In Europe “transit” is used as a synonym of “theodolite”. Americans use the term “theodolite” for more precise instruments.
In surveying for engineering projects, more sophisticated instruments are employed to maximize accuracy. For example, distances may be made by EDM or by tachymetry, a geometric technique in which the vertical distance on a graduated vertical staff, seen between two stadia hairs in the theodolite eyepiece, is a measure of the horizontal distance between the theodolite and the staff – usually 100 times the difference between the two readings.
Modern surveying instruments combine a theodolite, EDM equipment, and a computer that records all the observations and calculates the height differences obtained by measuring vertical angles.
Heights of surface features above sea level are determined by leveling. The surveyor’s level has been used by the surveyor for centuries. It consists of horizontal telescope fitted with cross hairs, rotating around a vertical axis on a tripod, with a very sensitive spirit level fixed to it; the instrument is adjusted until the bubble is exactly centered. It is used in conjunction with a graduated rod placed at the point to be measured and sighted through the telescope. If such rods are placed on successive ground points, and the telescope is truly level, the difference between the readings at the cross hairs will equal that between the heights of moving the level and the staffs alternately along a path or road and repeating this procedure, differences in height can be accurately measured over long horizontal distances.
Word list
facilitate | облегчать |
hydrographic survey | гидрографическая съёмка |
cadastral survey | кадастровая съёмка |
theodolite | теодолит |
transit | универсальный теодолит; тахеометр |
to upgrade | модернизировать; повышать уровень |
cost-effective | рентабельный, оправдывающий затраты |
to pivot | вращаться |
to graduate | градуировать |
graduation | градуировка |
sight | визирование; визировать; наблюдать |
line of sight | линия визирования |
circle | круг; лимб |
telescope | телескоп; зрительная труба |
tripod | штатив, тренога |
cross hairs | крест (сетка) нитей |
stadia hair | сетка нитей дальномера |
eyepiece | окуляр |
staff | рейка (с делениями) |
rod | рейка, веха |
bubble | пузырёк |
leveling | нивелирование |
to center | центрировать; выводить на середину пузырёк уровня |
readings | показания измерительных приборов; отсчёт (показаний) |
tachometer (tachymeter) | тахеометр |
technique | метод, способ выполнения |
successive | следующий один за другим; последовательный |
ground point | точка местности |
sophisticated | сложный, усложненный; современный |
I Pronounce correctly:
hydrographic; facilitate; superior; enhance; theodolite; vernier; micrometer; tachymetry; eyepiece; in conjunction.
II Complete the sentences:
1. … is used for measuring angles.
2. … is pivoted around horizontal and vertical axes.
3. Heights of surface are determined by … .
4. ... … consists of horizontal telescope on a tripod.
5. The instrument is adjusted until the … … is exactly centred.
III Find English equivalents of the following:
топосъёмка; гидрографическая съёмка; кадастровая съёмка; высококлассная оптика; точность наблюдений; точный оптический теодолит; при экстремальных климатических условиях; гарантировать необходимую точность; измерять горизонтальные и вертикальные углы; разумная цена.
IV Answer the questions:
1. What helped to facilitate surveys?
2. Why is classical theodolite still used?
3. What does theodolite consist of?
4. What do modern surveying instruments combine?
5. What is tachymetry?
6. What is leveling used for?
7. How does the surveyor’s level operate?
V Translate into English:
1. Облегчить съёмку помогает применение электронных приборов и компьютера.
2. Удивительно, что классические инструменты всё ещё применяются для проведения съёмки.
3. Эти инструменты не зависят от зарядки аккумулятора.
4. Для измерения углов обычно используется теодолит.
5. Углы считываются с горизонтального градуированного круга.
6. Нивелир снабжён чувствительным спиртовым уровнем.
VI Translate into Russian:
Geologic Surveying
Geologic surveying is the organized examination of an area for geologic data, It includes a topographic survey for making a base map, an aerial geologic survey to show the distribution of rock formation on the surface, a study of the structural geology showing the character of subsurface features and, by interpretation the historical geology showing the sequence of events that have taken place in geologic time.
It may include also special surveys such as one for economic geology to determine the location, extent, and exploitability of natural resources, and a hydrographic survey for measuring the flow of rivers and other streams.
UNIT 7
MEASURING OF DISTANCES
In small flat areas, working at large scales, it may be easier to measure the distance using a tape. This procedure was impractical over large and hilly areas until the invention of electromagnetic distance measurement (EDM) in the mid 20-th century. The procedure has made it possible to measure distances as accurately and easily as angles by electronically timing the passage of radiation over the distance to be measured; microwaves which penetrate atmospheric haze are used for long distances and light or infrared radiation for short ones.
In the devices used for EDM the radiation is either light (generated by a laser or an electric lamp) or an ultrahigh-frequency radio beam. The light beam requires a clear line of sight; the radio beam can penetrate fog, haze, heavy rain, dust, sandstorms, and some foliage. Both types have a transmitter-receiver at one survey station. At the remote station the light type contains a set of corner mirrors; the high-frequency type incorporates a retransmitter (requiring an operator) identical to the transmitter-receiver at the original station. A corner mirror has the shape of the inside of a corner of a cube; it returns light toward the source from whatever angle it is received, within reasonable limits. A transmitter must be aimed at the transmitter-receiver. In both types of instrument, the distance is determined by the length of time it takes the radio or light beam to travel to the target and back.
EDM has greatly simplified an alternative technique, called traversing for establishing a framework.
One of the several instruments used to measure the distance from the instrument to a selected point or object is a range finder. One basic type is the optical range finder. It is usually classified into two kinds, coincidence and stereoscopic.
The coincidence range finder, used chiefly in cameras and for surveying, consists of an arrangement of lenses and prisms set at each end of a tube with a single eyepiece at its centre. This instrument enables the user to sight an object by correcting the parallax resulting from viewing simultaneously from two slightly separated points. The object’s range is determined by measuring the angles formed by a line of sight at each end of the tube: the smaller the angles produced, the greater is the distance, and vice versa.
The stereoscopic range finder operates on much the same principle and resembles the coincidence type except that it has two eyepieces instead one. The design of the stereoscopic instrument makes it more effective for sighting moving objects. It was widely used for land-gunnery ranging during World War II.
Since the mid-1940, radar has supplanted optical range finders for most military target-ranging operations. This non-optical ranging device determines the distance to a target by measuring the time it takes radio pulses to reach the object, bounce off, and return.
Advances in laser technology led to the development in 1965 of another kind of ranging instrument known as the laser range finder. It has largely replaced coincidence range finders for surveying. The laser range finder, like radar, measures distance by timing the interval between the transmission and reception of electromagnetic waves, but it employs visible or infrared light rather than radio pulses. Such a device can measure distances of up to 1 mile (0.62 km) to an accuracy of 0.2 inch (0.5 cm). It is especially useful in surveying rough terrain where remote points have to be located between rocks and brush.
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