UNIT 1
GEODESY
The scientific objective of geodesy is to determine the size and shape of the Earth, the Earth’s gravity field and the precise location of positions. It involves determination of reference points on its surface. This requires surveying procedures of a high order of accuracy. For many centuries these studies were closely related to astronomy through observations of the sun, the moon, the planets and the stars. Until the advent of satellites, all geodesic work was based on land surveys made by triangulation methods employing a geodesic coordinate system (one used to study the geometry of curved surfaces). It is now possible to use satellites in conjunction with land-based system to refine knowledge of the Earth’s shape and dimensions; this field is sometimes termed satellite geodesy.
Positioning from space created a new era in Earth sciences. Studies of the orbits of the first satellites confirmed the bulging of the Earth at the equator and flattening at the poles. The low altitude of the first satellites offered the opportunity of studying the geometry of the Earth’s gravity field by direct observations of the satellite response to the field. In 1980s the Global Positioning System (GPS) was launched by the US Department of Defense, it is the latest step in space geodesy.
The practical role of geodesy is to provide a network of accurately surveyed points on the Earth’s surface, the vertical elevations and geographic positions of which are precisely known and, in turn, may be incorporated in maps. When two geographic coordinates of a control point on the Earth’s surface, its latitude and longitude, are known, as well as its elevation above sea level, the location of that point is known with an accuracy within the limits of error involved in the surveying process. In mapping large areas, such as whole state or country, the irregularities in the curvature of the Earth must be considered. A network of precisely surveyed control points provides a skeleton to which other surveys may be tied to provide progressively finer networks of more closely spaced points. The resulting networks of points have many uses, including bench marks for surveys of highways and other civil features. A major use of control points is to provide reference points to which the contour lines and other features of topographic maps are tied. Most topographic maps are made using photogrammetric techniques and aerial photographs.
Some of the observations made by the geodesists reveal important facts about the internal constitution of the Earth and this information is of great use in geological work.
Methods used by the geodesists for studying variations in density of the Earth’s crust are also used for locating mineral wealth. Seismological studies are an aid to engineers and architects in designing structures to resist earthquakes.
Word list
altitude | высота |
area | площадь; район, участок; местность |
bench mark | репер, тригонометрический пункт |
bulging | кривизна |
coordinate | координата |
geodesic coordinate system | сеть опорных геодезических пунктов |
elevation | высота; превышение |
error | ошибка; погрешность |
flat | плоский |
flattening | эллиптичность (сжатие) Земли; полярное сжатие |
positioning | позиционирование; ориентация; определение положения |
geodesy | геодезия; геод. измерения |
satellite ~ | спутниковая геодезия; |
GPS (global positioning system) | глобальная навигационная спутниковая система |
gravity field | гравитационное поле |
incorporate | включать; соединять |
land-based system | наземная система |
latitude | широта |
longitude | долгота |
network | сетка, сеть |
skeleton | план, схема |
geographic coordinates | географические координаты |
feature | особенность местности; элемент рельефа |
accuracy | точность |
high order of ~ | высокая степень точности |
аccurate | точный |
irregularities | неровность; неправильная форма |
locate | устанавливать точное местоположение; размещать |
location | местоположение; определение местоположения |
objective | цель, намерение |
precise | точный |
precision | точность |
point | точка |
control ~ | опорная точка; геод. пункт; репер; высотная отметка |
reference ~ | опорная точка; исходный ориентир |
closely spaced ~ | близко расположенные точки |
refine knowledge | совершенствовать знания |
resist earthquakes | выдерживать землетрясение |
tie | привязка; привязывать; соединять |
geodetic ~ | геод. привязка; привязка отдельных геод. систем |
triangulation | триангуляция |
survey | съёмка; производить съёмку |
object | предмет, объект |
Exercises
I Pronounce correctly:
оbject, objective; procedure; observe, observation, observatory; triangle, triangulation; launch; bulging; equator; curve, curvature; contour; photogrammetry, photogrammetric, photograph; technique, technician, technics, technology; architect; earth, earthquake; era; area; geodesy, geodetic, geodesic, geodesist; survey, surveying, surveyor.
II Find Russian equivalents of the following:
точное местоположение; опорная точка, наземная съемка; совершенствовать знания о форме Земли; определение местоположения из космоса; орбита спутника; гравитационное поле; глобальная навигационная спутниковая система; создавать сеть опорных точек; в пределах допустимой ошибки; гражданские объекты; внутреннее строение Земли; проектирование сейсмостойких сооружений; высотная отметка (тригонометрический пункт с высотой, определенной геометр. нивелированием); цель.
III Complete the sentences:
1. … created a new era in Earth sciences.
2. GPS was launched in ….
3. The objective of geodesy is to determine the size and shape of …
4. In mapping large areas ….. must be considered.
5. A major use of control points is to provide ….. …..
IV Answer the questions:
1. What is the scientific objective of geodesy?
2. What was geodesic work based on before the advent of satellites?
3. When did the new era in Earth sciences begin?
4. What does GPS mean?
5. What is the practical role of geodesy?
6. What is location of the point?
7. What does the network of surveyed points provide?
V Translate into English:
1. Научная цель геодезии – определение размера и формы Земли, её гравитационного поля и точного местоположения точек.
2. Глобальная навигационная спутниковая система была создана министерством обороны США.
3. Практической задачей геодезии является создание сети контрольных точек на Земле.
4. При составлении карты больших площадей, таких как целая страна, необходимо учитывать кривизну Земли.
5. Определение местоположения из космоса открыло новую эру в науках о Земле.
6. Сеть опорных точек может использоваться для многих целей, включая установку реперов для строительства шоссе.
7. Топографические карты создаются с помощью фотограмметрических приборов.
VI Translate into Russian:
Edmund Gunter
Edmund Gunter is an English mathematician of the 17th century who invented many useful measuring devices including a forerunner of a sliding rule. He was a professor of astronomy at Gresham College in London.
Gunter’s practical inventions included Gunter’s chain, measuring device and arbitrary measurement unit still widely used for surveying in English-speaking countries. Gunter’s chain is 22 yards (about 20 m) long and divided into 100 links. Each link is a solid bar. Measurement of the public land system of the U. S. and Canada is based on Gunter’s chain. An area of 10 square chains is equal to 1 acre.
Gunter’s quadrant was used to find the hour of the day, the sun’s azimuth and altitude of the object in degrees. Gunter’s scale or Gunter’s line, generally called the gunter by seamen, was a large plane scale with logarithmic divisions plotted on it. With the aid of a pair of compasses it was used to multiply and divide.
UNIT 2
EARTH
The Earth is one of the group of planets which revolve around a common central orb – the Sun. The definition of the figure of the Earth – i. e. its size and shape – usually does not involve the description of mountains and valleys but, rather, the size and shape of the mean sea level surface and its continuation under the land. This hypothetical surface, called a geoid, is a surface from which topographic heights and ocean depths are measured.
Because of gravity anomalies the geoid is irregular; however it is very nearly the surface generated by the ellipse rotating on its minor axis – i. e. an ellipsoid slightly flattened at the ends, or oblate. Such a figure is called spheroid. This oblate spheroid has a polar diameter about 27 miles (43 kilometres) less than its diameter at the equator.
The geoid is not a uniform spheroid however because of the existence of irregularities in the attraction of gravity from place to place on the Earth’s surface. These irregularities of the geoid would bring about serious errors in the surveyed location of control points, if astronomical methods which involve use of the local horizon, were used solely in determining locations. Because of these irregularities, the reference surface used in geodesy is that of a regular mathematical surface, an ellipsoid of revolution that fits the geoid as closely as possible. This reference ellipsoid is below the geoid in some places and above it in others. Over the oceans mean sea level defines the geoid surface, but over the land areas, the geoid is an imaginary sea-level surface. It is everywhere perpendicular to the pull of gravity.
The simplest methods by which the dimensions of the spheroid can be determined is by the measurement of two meridian arcs. The length of each arc and the latitudes of the terminal points of each must be measured.
Today perturbations in the motions of artificial satellites are used to define the global geoid and gravity pattern with a high degree of accuracy. Geodetic satellites are positioned at a height of 700 – 800 kilometres above the Earth. Simultaneous range observations from several laser stations fix the position of a satellite, and radar altimeters measure directly its height over the oceans. Results show that the geoid is irregular: in places its surface is up to 100 metres higher than the ideal reference ellipsoid and elsewhere it is as much as 100 metres below it. The most likely explanation for this height variation is that the gravity ( and density) anomalies are related to mantle convection and temperature differences at depth.
It is well known that the shape of the Earth is continuously changing mainly due to the slow loss of heat from its interior and through the gravitational interaction with the Sun, the Moon, and the planets. Global plate motion, volcanic and earthquake activities, changes in the Earth rotation and the orientation of its axis are all aspects of geodynamic processes that change the shape of the Earth. These phenomena call for a measurement precision of better than a few centimetres on a global scale.
Word list
Earth orb geoid spheroid ellipsoid reference-ellipsoid height axis oblate arc satellite bring about regular perturbation position surfacе reference surface level mean sea level altimeter earthquake | земной шар; Земля (планета) светило геоид сфероид эллипсоид референц-эллипсоид высота, высотная отметка ось cплющенный, сжатый у полюсов дуга спутник вызывать, быть причиной правильный пертурбация (отклонение в движении небесного тела вокруг к-л центрального тела, вызываемое притяжением других небесных тел) положение, местонахождение; определять местонахождение; локализировать поверхность уровенная поверхность; исходный уровень уровень, нивелир средний уровень моря высотомер, альтиметр землетрясение |
Еxercises
I Pronounce correctly:
earth; surface; earth’s surface; earthquake; equal, equator; spheroid, ellipsoid; hypothetical; diameter; perpendicular; artificial; satellite; high, height; interior; phenomenon, phenomena; simultaneous; geoid, geodesy, geodynamic; base, based, basic, basis.
II Find Russian equivalents of the following:
фигура Земли; средний уровень моря; гипотетическая поверхность; сила притяжения; с высокой степенью точности; искусственные спутники; фиксировать местоположение спутника; уровенная поверхность; конечные точки.
Ш Say if the statements are true or false:
1. The Sun revolves round the Earth.
2. Geoid is a hypothetical surface of the figure of the Earth.
3. The equator diameter is less than the polar diameter.
4. The geoid is a uniform spheroid.
5. The reference-ellipsoid is below the geoid in some places and above it in others.
IV Answer the questions:
1. What is the Earth?
2. What is meant by the figure of the Earth?
3. How is the hypothetical surface of the earth called?
4. What is spheroid?
5. Are the polar and equatorial diameters equal?
6. Why isn’t geoid a uniform spheroid?
7. What reference surface is used in geodesy?
8. How is the global geoid and gravity pattern defined now?
9. Why is the shape of the Earth continuously changing?
V Translate into English:
1. Земля – это планета, которая вместе с другими планетами вращается вокруг общего светила – Солнца.
2. Гипотетическая поверхность Земли называется геоидом.
3. Геоид приближается по форме к эллипсоиду, сплющенному с двух сторон. Такая фигура называется сфероидом.
4. Полярная ось земли на 43 км меньше, чем экваториальная.
5. В геодезии используется уровенная поверхность эллипсоида вращения, называемого референц-эллипсоидом.
6. Гравитационные аномалии вызваны разницей температур внутри Земли и конвекцией мантии Земли.
7. Форма Земли постоянно изменяется из-за понижения температуры внутри Земли и гравитационного взаимодействия с Солнцем, Луной и другими планетами.
VI Translate into Russian:
Geomorphology
Geomorphology is a scientific discipline concerned with the description and classification of the Earth’s topographic features.
Much geomorphologic research has been devoted to the origin of landforms. Such studies focus on the forces that mold and alter the primary relief elements of the terrestrial surface. These forces include tectonic activity and earth surface movements. In recent years increasing attention has been given to the effects of human action on the physical environment as well.
Geomorphology is closely allied with a number of other scientific disciplines that are concerned with natural processes: atmospheric sciences, soil chemistry, geophysics and volcanology. The study of human impact upon landforms relies on the disciplines of geography and human ecology.
UNIT 3
SURVEYING
Surveying is a method of making relatively large-scale measurements of the Earth’s surface. To survey means “to determine the boundaries, position and an area of the land by measuring angles and distances and applying the principles of mathematics.” Surveying is divided into the categories of plane surveying and geodetic surveying. Plane surveying concentrates on mapping relatively small areas (smaller than 20 km across), where the curvature of the Earth is not a significant factor, the calculations of plane trigonometry are sufficient. Geodetic surveying covers large areas of the globe, with all attendant corrections for the curvature of the Earth; such surveying must be very accurate, and geodetic instruments are precise.
Measurements made in the direction of gravity are designated as vertical, and measurements made perpendicular to the direction of gravity are designated as horizontal. Surveying measurements are of four types: (1) horizontal lengths or distances, (2) vertical lengths, or differences in height or elevation, (3) horizontal angles measured in horizontal planes, and (4) vertical angles measured in vertical planes.
Horizontal lengths are generally measured in short, straight sections, that together form short arcs along the Earth’s surface. With a surveyor’s level, the difference in height between two points can be determined. Directions are given in azimuths or bearings.
Surveying of land areas. Land-area surveys are made to determine the relative horizontal and vertical position of topographic features and to establish reference marks to guide construction or to indicate land boundaries. Reconnaissance of the area is followed by a preliminary survey; a map and then a plan are prepared based on the preliminary survey; and finally a location survey is made, based on the plan. Surveys to establish property boundaries involve a thorough knowledge of real-estate laws as well as skills in survey techniques.
Surveying, in which the facts are discovered and recorded, must precede mapping, in which the facts are presented in graphic form. Surveying involves (1) global positioning, in which the area to be mapped is located on the Earth’s surface, usually by fixing a number of points in the area by astronomic observations or, after the techniques became available, by satellite or radar procedures; (2) establishing the framework, in which these points, and commonly many others connected by some combination of distance and angle measurements, are integrated into an accurately defined structure – like the steel framework of a modern building – on which the detail survey is based; and (3) making the detail survey, which establishes by less accurate (and therefore cheaper) methods the relative positions and shapes of the features being mapped. Constant reference to the framework prevents the errors in the detail survey from accumulating and growing unacceptably large.
The maps and the data produced by the surveyors are used by civil engineers in many ways. Before construction begins the exact position of the various parts of the dam, of the track of the railway or road, are fixed on the ground by using normal surveying methods. In choosing the site for the dam, for instance, an engineer can study on a map the courses of rivers and streams in the reading the contours he can calculate the amount of water which can be stored by building the dam of a given height in a certain place. In the same way the results of a soil survey clearly marked on a map will give the engineer vital information about the foundations. When deciding the route of a railway or road, the gradients, radii of curves, heights of embankments and depth of cutting can be calculated from data supplied by the surveyor.
Word list
scale | масштаб, шкала |
boundary | граница |
property ~ | граница частных владений |
designate | обозначать |
survey | съёмка; производить съёмку |
plane ~ | съёмка плана, съёмка без учета кривизны |
geodetic ~ | геодезическое обоснование съёмки |
land area ~ | наземная съёмка, топографическая съёмка |
preliminary ~ | подготовительная (предварительная) съёмка |
location ~ | топографическая оценка местности, разбивка трассы |
detail ~ | детальная (подробная) съёмка; крупномасштабная съёмка |
feature | черта, элемент рельефа |
map | карта; картографировать, составлять карту |
mapping | картографирование, составление карты |
real estate | недвижимость |
framework | сеть опорных точек; основа построения |
reconnaissance | рекогносцировка, разведка |
site | местоположение; место для застройки |
civil engineer | инженер-строитель |
gradient | наклон |
surveyor’s level | нивелир |
I Pronounce correctly:
measure, measured, measuring, measurement; surface; curve, curvature; significant; trigonometry; perpendicular; thorough; reconnaissance; technique, technician, technology; unacceptable; sufficient; preliminary.
II Find English equivalents of the following:
крупномасштабные измерения; определять границы; применять принципы математики; перпендикулярный направлению гравитации; определять разность высот; изображать графически; предшествовать составлению карт; место для строительства дамбы; глубокие знания.
III Complete the sentences:
1. … survey is used when the curvature of the Earth is not important.
2. … survey covers large areas, when the curvature must be taken into account.
3. Directions are given in … .
4. A map is made on the basis of … .
5. The maps produced by … are used by civil engineers.
IV Answer the questions:
1. What is surveying?
2. What are the two categories of surveying?
3. What is plane surveying?
4. What is geodetic surveying?
5. What measurements are called vertical?
6. What types of surveying measurements are horizontal?
7. How are directions given?
8. What is the purpose of land surveys?
9. How are facts presented on the map?
V Translate into English:
1. Производить съёмку – значит определять местоположение границ и протя-жённость территории с помощью измерения углов и расстояний, применяя принципы математики.
2. При картографировании относительно небольших участков Земли произво-дится съёмка без учета кривизны Земли.
3. Геодезическое обоснование необходимо при съемке больших по площади территорий.
4. Разность высот двух точек определяется с помощью нивелира.
5. Карта готовится на основании предварительной съёмки.
6. Факты на карте представлены в графической форме.
7. Прежде чем приступить к строительству точное положение объекта фикси-руется на Земле с помощью съёмки.
VI Translate into Russian:
Triangulation
Triangulation is used in navigation, surveying and civil engineering as a technique for precise determination of distances and angles for location of a ship’s or aircraft’s position, and in such endeavours as road building, tunnel alignment, and other construction. It is based on the laws of plane trigonometry, that if one side and two angles of a triangle are known, the other two sides and angle can be readily calculated. One side of the selected triangle is measured. This is the baseline. The two adjacent angles are measured by means of a surveying device known as a theodolite, and the entire triangle is constructing a series of such triangles, each adjacent to at least one other, values can be obtained for distances and angles not otherwise measurable.
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