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Concept of theodolite operation
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Topical vocabulary:
| angle | угол | to flip over | плавать, переворачивать(ся) |
| plane | плоскость | construction site | строительная площадка |
| focal plane | фокальная плоскость | to plunge | падать |
| axis (axes) | ось (оси) | to align | выравнивать |
| perpendicular axes | перпендикулярные оси | index error | двойная коллимационная ошибка |
| sight axis | оптическая ось (визирная) | collimation | коллимация |
| surveying | геодезические изыскания, съёмка | crosshairs | сетка нитей |
| to measure | измерять | to adjust | регулировать |
| precision | точность | adjustment | регулировка, адаптация |
| precise electronic theodolites | точные электронные теодолиты | to refine | усовершенствовать |
| builder’s level | строительный нивелир | refinement | усовершенствование |
| transit | тахеометр | calibration | калибровка |
| lightweight tool | легкое переносное устройство | to eliminate | удалить, сократить, свести к минимуму |
| graduated circle | градуированная окружность (с делениями) | elimination | уменьшение, сокращение |
| scale | масштаб | plumb bob | отвес (груз, гиря) |
| scale magnification | увеличение масштаба | plummet | отвес (лазерный) |
| spirit level | (спиртовой) уровень | screw | винт |
| lens | линза | footscrew | подъёмный винт |
| tubular spirit bubble | спиртовой пузырёк в трубке | thumbscrew | наводящий винт |
| tribrach | трегер | adjusting screw | юстировочный винт |
| rocket launch | запуск ракет | tripod | штатив |
Text
A theodolite is a precision instrument for measuring angles in the horizontal and vertical planes. Theodolites are mainly used for surveying applications, and have been adapted for specialized purposes in fields like meteorology and rocket launch technology. A modern theodolite consists of a movable telescope mounted within two perpendicular axes — the horizontal axis and the vertical axis. When the telescope is pointed at a target object, the angle of each of these axes can be measured with great precision, typically to seconds.
Transit refers to a specialized type of theodolite developed in the early 19th century. It featured a telescope that could "flip over" ("transit the scope") to allow easy back-sighting and doubling of angles for error reduction. Some transit instruments were capable of reading angles directly to thirty seconds. In the middle of the 20th century, "transit" came to refer to a simple form of theodolite with less precision, lacking features such as scale magnification and micrometers. Although precise electronic theodolites have become widespread tools, the transit still finds use as a lightweight tool on construction sites. Some types of transits do not measure vertical angles.
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The builder's level is often mistaken for a transit, but it measures neither horizontal nor vertical angles. It uses a spirit level to set a telescope level to define a line of sight along a level plane.
Both axes of a theodolite are equipped with graduated circles that can be read through magnifying lenses. The vertical circle which 'transits' about the horizontal axis should read 90° (100 grad) when the sight axis is horizontal, or 270° (300 grad) when the instrument is in its second position, that is, "turned over" or "plunged". Half of the difference between the two positions is called the "index error".
Diagram of an Optical Theodolite
The horizontal and vertical axes of a theodolite must be perpendicular; if not then a "horizontal axis error" exists. This can be tested by aligning the tubular spirit bubble parallel to a line between two footscrews and setting the bubble central. A horizontal axis error exists if the bubble runs off central when the tubular spirit bubble is reversed (turned through 180°).
To adjust, remove half the amount the bubble has run off using the adjusting screw, then relevel, test and refine the adjustment.
The optical axis of the telescope, called the "sight axis", defined by the optical center of the objective lens and the center of the crosshairs in its focal plane, must also be perpendicular to the horizontal axis. If not, then a "collimation error" exists.
Index error, horizontal axis error and collimation error are regularly determined by calibration and are removed by mechanical adjustment. Their existence is taken into account in the choice of measurement procedure in order to eliminate their effect on the measurement results.
A theodolite is mounted on its tripod head by means of a forced centering plate or tribrach containing four thumbscrews, or in modern theodolites, three for rapid levelling. Before use, a theodolite must be precisely placed vertical above the point to be measured using a plumb bob, optical plummet or laser plummet. The instrument is then set level using levelling footscrews and circular and more precise tubular spirit bubbles.
Practical work № 3
I. Give the Russian equivalents to the following:
1) a theodolite is mounted on its tripod;
2) parallel to a line between two footscrews;
3) tribrach contains four screws, or in modern theodolites, three;
4) half of the difference between the two positions;
5) rocket launch technology;
6) movable telescope mounted within two perpendicular axes;
7) some transit instruments were capable of reading angles directly to thirty seconds;
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8) precise electronic theodolites;
9) it measures neither horizontal nor vertical angles;
10) calibration and mechanical adjustment;
11) to eliminate the effect on measurement results;
12) a theodolite must be precisely placed vertical.
II. Find the English equivalents to the following phrases in the text given:
1) точные электронные теодолиты;
2) коллимационная ошибка;
3) лёгкое переносное устройство;
4) строительный нивелир;
5) увеличивающие линзы;
6) перпендикулярные оси;
7) технология запуска ракет;
8) специализированный тип теодолита;
9) разница между двумя показаниями;
10) с меньшей точностью;
11) механическая регулировка;
12) процедура измерений.
III. Find the English equivalents in the text:
1) Хотя точные электронные приборы получили широкое распространение, теодолиты до сих пор используются как переносные приборы на строительных площадках.
2) Обе оси теодолита снабжены градуированными окружностями, которые можно считать с помощью увеличивающих линз.
3) Современный теодолит состоит из движущейся трубы, помещённой между двумя перпендикулярными осями - горизонтальной осью и вертикальной осью.
4) Строительный нивелир часто ошибочно принимают за тахеометр, но он не измеряет ни горизонтальных, ни вертикальных углов.
5) Горизонтальные и вертикальные оси теодолита должны быть перпендикулярны, в противном случае возникает «ошибка цилиндрического уровня».
VI. Answer the questions:
1) What is a level?
2) What is a theodolite?
3) What is a transit?
4) What are constituent elements of a theodolite?
Thank you!
Criteria of marks:
16 –22 - “satisfactory”
23-30 – “good”
31-33 – “excellent”
Post-reading exercises:
Exercise 1. Answer the questions using information from the text:
1) What is a theodolite?
2) What does a theodolite consist of? (What are the elements of a theodolite?)
3) What spheres are theodolites used in?
4) What is “an index error”?
5) What is “a horizontal axis error”?
6) What is “a collimation error”?
7) How can these errors be removed?
Exercise 2. Retell the text “ CONCEPT OF THEODOLITE OPERATION” using the questions above.
Unit 5
COMPONENTS OF MAPS
Topical vocabulary:
| title (of a map) | название (карты) |
| to represent | обозначать (на карте) |
| hydrography | гидрография |
| vegetation | растительность |
| relief | рельеф |
| latitude | широта |
| longitude | долгота |
| to measure distances | измерять расстояния |
| legend (key) | легенда карты; пояснения за рамкой карты; |
| legend of symbols | таблица условных знаков |
| grid | сетка (координат) |
| observatory | обсерватория |
| map projection | картографическая проекция |
| cylindrical map projection | цилиндрическая проекция |
| conical map projection | коническая проекция |
| azimuthal map projection | азимутальная проекция |
| Mercator map projection | прямая равноугольная цилиндрическая проекция Меркатора |
| to devise | разрабатывать |
| distortion | искажение |
| scale | масштаб |
Pre-reading exercises:
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Составьте словосочетания и предложения, используя тематический словарь:
- название (наименование) карты;
- название карты даёт информацию о территории;
- обозначить на карте;
- коричневый цвет обозначает рельеф на карте;
- зелёный цвет обозначает растительность;
- голубым цветом изображается гидрография;
- вертикальные линии на глобусе обозначают долготу;
- горизонтальные линии на карте обозначают широту;
- измерить расстояние на карте (с помощью линейки);
- измерить расстояние (с помощью тахеометра);
- масштаб позволяет измерить расстояние на карте;
- используйте таблицу условных знаков;
- студенты создают сетку координат;
- пересекать Гринвич;
- нулевой меридиан проходит через Гринвич;
- начертить картографическую проекцию;
- искажение изображения; изображение имеет множество искажений.
Text
Despite their variety, all maps have similar components. These include a title; a legend or key; a direction indicator; and a scale.
The title of a map identifies what the map is about and what parts of the earth it shows. The title of some maps includes a date. Dates are useful on maps showing features that change over time. A map with the title “Distribution of Population in France: 1920”, for example, should not be used when looking for information of the present population of France.
A legend or key explains the meaning of colours and symbols used on a map. A map with areas shown in green, red and blue might be misunderstood unless the user knows what the green, red and blue represent (blue for hydrography, green for vegetation, red for man-made features and brown – for relief). The legend also explains the meaning of symbols used on a map, such as stars for capital cities.
Every map should have a direction indicator. One such indicator is an arrow that points north. A different way to find directions on a map is to study the parallels and meridians. East and west directions follow parallels, or lines of latitude. North and south directions follow meridians, or lines of longitude. Parallels and meridians cross each other to form an imaginary grid over the earth. Because each degree can be broken into 60 minutes (`) and each minute into 60 seconds (``), this grid can be used to fix the precise location of any point on the earth’ surface.
The most important longitude is called the Greenwich Meridian, because it passes through a place called Greenwich in London where there is a famous observatory. The longitude of Greenwich meridian is 0 degrees. At Greenwich local time is called Greenwich Mean Time (GMT). All places on the same meridian have the same local time. When it is noon at a given meridian, it is after noon or post meridiem (p.m.) at places which lie to the east of it. This is because the earth rotates from west to east. At the same time the sun will be before noon or ante meridiem (a.m.) at places lying to the west.
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Maps scales and projections. A map scale provides statistical information used to measure distances on a map. While maps have similar components, they do not always show areas of the world in exactly the same way. The size and shape of North America, for example, may look somewhat different on two different maps. The differences occur because the two maps use different map projections, or methods by which the features of the earth’s curved surface are transferred onto a flat map.
A great variety of map projections has been devised to provide for the various properties that may be desired in maps. A projection is a systematic method of drawing the Earth’s meridians and parallels on a flat surface. Most types of projection can be grouped according to their geometric derivation as cylindrical, conic or azimuthal.
No matter which projection is used, every map has some distortions that are inevitable in the process of illustrating the earth’s spherical surface on a flat map.
Practical work № 4
I Find English equivalents of the following:
1) изменяться со временем;
2) плоская поверхность;
3) столичные города;
4) точное местоположение;
5) переносить на бумагу;
6) на поверхности Земли;
7) условное обозначение;
8) местное время;
9) сферическая поверхность;
10) таким же образом;
11) искажения неизбежны.
II Fill in the gaps with the proper words:
1) The … of the map identifies what the map is about.
2) … colour on a map represents vegetation.
3) The most important longitude is called the …. Meridian.
4) … is a systematic method of drawing meridians and parallels on a flat surface.
5) The components similar for all the maps are title, direction indicator and ….
III Answer the questions:
1) What similar components do all the maps include?
2) What does the title of a map identify?
3) What does the legend explain?
4) What information does the map scale provide?
5) Where is the most important longitude situated?
6) What is GMT?
IV Find the English equivalents to the following sentences:
1) Любая карта имеет название, масштаб и легенду.
2) По названию карты понятно, какую часть Земли она изображает.
3) Легенда карты объясняет значения условных знаков.
4) По сетке координат можно определить точное местоположение любой точки на поверхности Земли.
5) Долгота Гринвичского меридиана – 0 градусов.
6) Масштаб дает статистическую информацию для определения расстояния по карте.
Thank you!
Criteria of marks:
14 –19 - “satisfactory”
20 - 25 – “good”
26 - 28 – “excellent”
Post-reading exercises:
Exercise 1. Answer the questions using information from the text:
1) What are components of a map?
2) What does the title identify?
3) What does the legend explain?
4) What do blue, green and brown colours represent on the map?
5) What is a direction indicator?
6) What is GMT?
7) What information does the scale provide?
8) Why have maps got distortions?
Exercise 2. Retell the text “ COMPONENTS OF MAPS ” using the questions above.
Unit 6
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