Text 1. General characteristic of Geodesy

Geodesy is one of the oldest natural sciences which involve the study of the Earth’s shape and its gravity field. It provides the scientific basis of precise surveying navigation, mapping and charting, and studies of the physics and dynamics of the Earth.

The History of Geodesy. Throughout the history the shape of the Earth has been discussed by scientists and philosophers. By 500 B.C. most scholars thought the Earth was completely spherical. The Greek philosopher Aristotle was the first person who calculated the size of the Earth by determining its circumference (the length around the equator).

As technology developed, scientists began to use different techniques to measure distance. The English thought the Earth was oblate or flattened at the poles. It was proved that Newton was right. The earth is flattened into the shape of an oblate sphere.

During the last 100 years, geodesy and its application have advanced tremendously. The 20^th century brought space-based technology, making geodetic measurements extremely precise. Today satellites allow scientists to measure changes in the Earth’s surface to the centimeter.

The Elements of Geodesy. The Figure of the Earth. The Earth is nearly spherical with a radius of about 3,963 miles (6,378 km), and its surface is very irregular. Mountains and valleys make actually measuring this surface impossible, because an infinite amount of data would be needed.

To measure the Earth, geodesists use a theoretical mathematical surface called the ellipsoid. Because the ellipsoid exists only in theory and not in real life, it can be completely smooth and doesn’t take any irregularities – such as mountains or valleys into account. The ellipsoid is created by rotating an ellipse around its shorter axis. This matches the real Earth’s shape, because the Earth is slightly flattened at the poles and bulges at the equator. The ellipsoid is only a mathematical concept. Geodesists need to account for the reality of the Earth’s surface. To meet this need, the geoid, a shape that refers to global mean sea level was created although a geoid may seem to be smooth, regular shape but because of variations in gravitational force, the “height” of different parts of geoid is always changing, moving up and down in response to gravity.

Exercise 2. Look through the words and try to remember their meaning:

to involve —поєднувати, містити в собі

to bulge —випинатися

shape —форма

gravity —гравітація

gravitational force —гравітаційна сила

gravity field —гравітаційне поле

spherical —сферичний

circumference —коло, периферія

flattened —сплющений

oblate sphere —сплющена сфера

geodetic measurements —геодезичні вимірювання

satellite —супутник

ellipsoid —еліпсоїд

shorter axis —мала вісь

geoid —геоїд

variation —відхилення

scholar —учений

smooth —гладкий, рівний

precise —точний, визначений, чіткий

Exercise 3. Answer the following questions:

1. What is geodesy as a science?

2. Who was the first person who calculated the size of the Earth by determining its circumference?

3. Why it was proved that Newton was right?

4. What did the 20^th century bring?

5. What is the radius of the Earth?

6. What theoretical mathematical surface did the geodesists use to measure the Earth?

7. Why did the geodesists chose geoid?

Exercise 4. Translate the following word combinations:

gravity field, surveying navigation, mapping and charting, different techniques, oblate sphere, making geodetic measurements, real Earth’s shape, mathematical concept, to be flattened at poles, global mean sea level, regular shape, to meet the need.

Exercise 5.Complete the following chart:

Verb	Noun	Adjective
to discuss
to determine
to develop
to differ
to use		useful
to measure
to change
to improve	improvement

Exercise 6. Look through the following verb forms and define the tense, write the infinitive of the verb:

has been discussed, thought, developed, began, was proved, have advanced, would be needed, is created, may seem, is always changing.

Exercise 7. Put verbs in the brackets in the correct form:

1. Throughout the history the shape of the Earth _______ (to be) discussed by scientists and philosophers.

2. By 500 B.C. most scholars_____(to think) the Earth was completely spherical.

3. As technology developed, scientists _______ (to begin) to use different techniques to measure distance.

4. It _________ (to be) proved that Newton was right.

5. During the last 100 years, geodesy and its application____________ (to advance) tremendously.

6. The ellipsoid _______(to be) created by rotating an ellipse around its shorter axis.

7. The ellipsoid _______(to be) only a mathematical concept.

Exercise 8. Read and translate the text.

Text 2. The Types of DATA

In geodesy two types of data must be considered.

Datum is the basis for all geodetic survey work. They act as reference points in the same way as starting points do when give someone directions. For instance, when you want to tell someone how to get to your house, you give them a starting point that they know, like a road or building. Geodesists and surveyors use datum as starting or reference points when they create maps, mark off property boundaries, and plan, design and build roads, bridges and other structures.

Another way to think about a datum is as a set of information that acts as a foundation for other data. For example, when a skyscraper is about to be built, the construction team must first build the foundation. Without this element, skyscraper would be unstable and unsafe. This is the same concept as a datum. While a datum is a mathematical and geometric concept, it acts like the concrete foundation of a skyscraper.

In geodesy, two main types of data must be considered. These data are called the horizontal and vertical datum. The horizontal datum is a collection of specific points on the Earth that have been identified according to their precise northerly or southerly location (latitude) and easterly or westerly location (longitude).

To create the horizontal datum surveyors marked each of the positions they had identified, typically with a brass, bronze or aluminum disk or monument.

These markers were placed so that surveyors could see one marked position after another.

To “connect” the horizontal monuments into a unified network or datum, surveyors have used a variety of methods including triangulation.

The Vertical Datum. The vertical datum is a collection of specific points on the Earth with known heights either above or below mean sea level. In areas far away from the shore mean sea level is determined by the shape of the geoid.

Markers are used to identify known positions in the horizontal datum, round brass plates mark positions in the vertical datum. The traditional method for setting these vertical benchmarks is called differential leveling. This method uses a known elevation at one location to determine it at another location.

One of the main uses of the vertical datum is to measure rates of subsidence or land sinking. By means of the vertical datum officials can determine the true elevation and position of the hurricane evacuation routes.

Exercise 9. Look through the words and try to remember their meaning:

data —дані

surveyor —маркшейдер, топограф

datum —дана величина

to create maps —створювати карти

property boundaries —межі власності

horizontal datum —горизонтальна вісь координат

vertical datum —вихідний горизонт

brass —латунь

to triangulate —робити триангуляцію

triangulation —триангуляція, тригометрична зйомка

vertical benchmark —відмітка, оцінка висоти

differential leveling —геометричне нівелювання

land sinking —усадка землі

subsidence —осідання

evacuation routes —шляхи евакуації

Exercise 10. Answer the following questions:

1.What types of data must be considered in geodesy?

2. How do they act?

3. When do the geodesists and surveyors use data?

4. What is the same concept as datum?

5. How can you explain the meaning of the horizontal datum?

6. What did the geodesists and surveyors do to create the horizontal datum?

7. How can you explain the term “the vertical datum”?

8. What is the main use of vertical datum?

Exercise 11. Translate the following word combinations:

geodetic survey work, starting points, a set of information, mathematical and geometric concept, concrete foundation, horizontal and vertical

datum, southerly location, easterly or westerly location, the horizontal monuments, above or below mean sea level, rates of subsidence.

Exercise 12. Complete the following chart:

Verb	Noun	Adjective
to survey
to refer
to create		creative
to mark	marker
to mean
to build
to connect

Exercise 13. Look through the following verb forms and define the tense, write the infinitive of the verb:

must be considered, do, to be built, acts, are called, have been identified, marked, had identified, were placed, have used, is determined, known, uses, can determine.

Exercise 14. Put verbs in the brackets in the correct form:

1. Datum_______ (to be) the basis for all geodetic survey work.

2. Without this element, skyscraper ________(to be) unstable and unsafe.

3. These data _______ (to be) called the horizontal and vertical data.

4. This method ______ (to use) a known elevation at one location to determine it at another location.

5. To create the horizontal datum surveyors marked each of the positions they__________(to identify), with a brass, bronze or aluminum disk or monument.

6. One of the main uses of the vertical datum ________(to be) to measure rates of subsidence or land sinking.

Exercise 15. Read and translate the text.

Text 3. Gravity

Gravity is the force that pulls all the objects in the universe toward each other. On the Earth gravity pulls all the objects “downward’
toward the center of the planet. According to Sir Isaac Newton’s Universal Law of Gravitation, the gravitational attraction between two bodies is stronger when the masses of the objects are greater and closer together. This rule applies to the Earth’s gravitational field as well. Because the Earth rotates and its mass and density vary at different locations on the planet, gravity is also varied.

One reason why geodesists measure variations in the Earth’s gravity is because gravity plays a major role in determining sea level.

Geodesists calculate the elevation of locations on the Earth’s surface based on the mean sea level.

So knowing how gravity changes sea level helps geodesists make more accurate measurements.

In areas of the planet where gravitation is stronger, the mean sea level will be higher. In areas where the Earth’s accurate measurements are weaker, the mean sea level will be lower.

To measure the Earth’s gravity field, geodesists use instruments in space and on land. Space satellites gather data of gravitational changes as they pass over points on the Earth’s surface. On land devices called gravimeters measure the Earth’s gravitational pull on a suspended mass. With this data geodesists can create detailed maps of gravitational fields and adjust elevations on existing maps. Gravity principally affects the vertical datum because it changes the elevation of the land surface.

Exercise 16. Look through the words and try to remember their meaning:

gravity —сила тяжіння

gravitational attraction —гравітаційне притягання

gravitational field —гравітаційне поле

accurate measurements —точні вимірювання

mean sea level —середній рівень моря

density —щільність

to rotate —обертатися

to pass over —проходити повз

to create detailed maps —створювати детальні карти

to adjust elevations —вивіряти, встановлювати підняття

to affect —впливати

to calculate —обчислювати, розраховувати

to determine —визначати, встановлювати

Exercise 17. Answer the following questions:

1. What is gravity?

2. What does Sir Isaac Newton’s Universal Law of Gravitation tell us about?

3. Why do geodesists measure variations in the Earth’s gravity?

4. What do geodesists use to measure the Earth’s gravity field?

5. Where and how do satellites gather data of gravitational changes?

6. How can geodesists create detailed maps?

7. How does gravity principally affect the vertical datum?

Exercise 18. Translate the following word combinations:

gravitational attraction, gravitational field, mean sea level, gravity changes, accurate measurements, space satellites, land devices, suspended mass, elevation of the land surface.

Exercise 19. Complete the following chart:

Verb	Noun	Adjective
to attract
to rotate
to vary		variable
to create
to calculate	calculation
to mean
to base
to change
to pass
to affect

Exercise 20. Look through the following verb forms and define the tense, write the infinitive of the verb:

applies, rotates, make, called, pull, can create, adjust, were detailed, affects, will be changed, is varied, has passed, have being made.

Exercise 21. Put verbs in the brackets in the correct form:

1. On Earth gravity ________(to pull) all the objects “downward’ toward the center of the planet.

2. This rule _________(to apply) to the Earth’s gravitational field as well.

3. Geodesists measure variations in the Earth’s gravity _____(to be) because gravity_______(to play) a major role in determining sea level.

4. So knowing how gravity changes sea level _____ (to help) geodesists make more accurate measurements.

5. Space satellites ______ (to gather) data of gravitational changes as they ________ (to pass) over points on the Earth’s surface.

6. Gravity principally _______ (to affect) the vertical datum because it changes the elevation of the land surface.

Exercise 22. Change the following sentences into Passive:

1. On the Earth gravity pulls all the objects “downward’ toward the center of the planet.

2. Geodesists calculate the elevation of locations on the Earth’s surface based on the mean sea level.

3. One reason why geodesists measure variations in the Earth’s gravity is because gravity plays a major role in determining sea level.

4. Space satellites gather data on gravitational changes as they pass over points on the Earth’s surface.

5. With these data geodesists can create detailed maps of gravitational fields and adjust elevations on existing maps.