Text 2 : Map Projection and Map Scale

The shape of the Earth's surface can be described as an ellipsoid. An ellipsoid is a three-dimensional shape that departs slightly from a purely spherical form. The Earth takes this form because rotation causes the region near the equator to bulge outward to space. The angular motion caused by the Earth spinning on its axis also forces the polar regions on the globe to be somewhat flattened.

Representing the true shape of the Earth's surface on a map creates some problems, especially when this depiction is illustrated on a two-dimensional surface. To overcome these problems, cartographers have developed a number of standardized transformation processes for the creation of two-dimensional maps. All of these transformation processes create some type of distortion artifact. The nature of this distortion is related to how the transformation process modifies specific geographic properties of the map. Some of the geographic properties affected by projection distortions include: distance; area; straight line direction between points on the Earth; and the bearing of cardinal points from locations on our planet.

Maps are rarely drawn at the same scale as the real world. Most maps are made at a scale that is much smaller than the area of the actual surface being depicted. The amount of reduction that has taken place is normally identified somewhere on the map. This measurement is commonly referred to as the map scale. Conceptually, we can think of map scale as the ratio between the distance between any two points on the map compared to the actual ground distance represented. This concept can also be expressed mathematically as:

On most maps, the map scale is represented by a simple fraction or ratio. This type of description of a map's scale is called a representative fraction. For example, a map where one unit (centimeter, meter, inch, kilometer, etc.) on the illustration represents 1,000,000 of these same units on the actual surface of the Earth would have a representative fraction of 1/1,000,000 (fraction) or 1:1,000,000 (ratio). Of these mathematical representations of scale, the ratio form is most commonly found on maps.

Scale can also be described on a map by a verbal statement. For example, 1:1,000,000 could be verbally described as "1 centimeter on the map equals 10 kilometers on the Earth's surface" or "1 inch represents approximately 16 miles".

Most maps also use graphic scale to describe the distance relationships between the map and the real world. In a graphic scale, an illustration is used to depict distances on the map in common units of measurement. Graphic scales are quite useful because they can be used to measure distances on a map quickly.

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

distortion-викривлення to modify- видозмінювати

distance- відстань to overcome- переборювати

fraction- дріб to bulge- витинатися

scale- масштаб to depart- відхилятися

measurement- вимірювання to affect- впливати

shape- форма to spin- обгортатися

globe- глобус ellipsoid- еліпсоід

polar- полюсний equator- екватор

axis- вісь rotation- обертання

angular- кутовий surface- поверхня

latitude- широта nautical- морський

longitude- довгота bias- нахил, сміщення

bearing- відношення (оріентац.) tangent-тангенс

Exercise 3. Answer the following questions:

1. What geometrical shape can the Earth be described?

2. Why does the Earth take this form?

3. What does the angular motion force?

4. Why does the representing the true shape of the Earth’s surface create some problems?

5. What have the cartographers develop to overcome these problems?

6. What do the transformation processes create?

7. What does the transformation process modify?

8. What are geographic properties affected by projection distortions?

9. What is the function of map scale?

10. What is a map scale?

11. How mathematically can you express the concept of map scale?

Exercise 5. Translate the following clusters, divide them into: “adjective+noun”and “noun+noun”:

map scale, actual surface, cardinal points, simple fraction, projection distortions, distortion artifact, actual ground distance, verbal statement, representative fraction, polar regions, two-dimensional surface, spherical form, angular motion, transformation processes, specific geographic properties, three-dimensional shape, graphic scale, distance relationships, standardized transformation processes.

Exercise 4. Complete the following chart.

geology	geologist	geological
geodesy
geography
geometry
geophysics

Exercise 5. Look through the following verb forms and define the tense, write the infinitive of the verb.

is used, represents, are described, depicted, was expressed, is called, are, has taken, will include, is related, created, have developed, forces, are drawn, took, will be identified, causes, was represented, is referred, had been found.

Exercise 6. Put vers in the brackets in the correct form.

1. A simple fraction or ratio ______ (to represent) the map scale on most maps.

2. Most maps also ______ (to use) graphic scale to describe the distance relationships between the map and the real world.

3. Weather map ________ (to display) the condition of the physical state of the atmosphere and its circulation at a specific time over a region of the Earth.

4. Cartography ________ (to study) map construction.

5. The Mollweide Projection _______ (to try) to present more accurate representations of area.

6. A small scale map _______ (to show) a large area with a small amount of detail.

7. The Sinusoidal Equal-Area Projection _______ (to represent) areas in their true form on a two-dimensional map.

8. Cartographers ______ (to talk) about large and small scale maps.

9. A large scale map ________ (to show) a small area with a large amount of detail.

Exercise 7. Change the following sentences into Passive.

1. Map construction ______ by students. (to explain/ every day)

2. Map construction _____ by students. (to explain/ now)

3. Map construction _______ by students. (to explain/ tomorrow/ by 12 o’clock)

4. The spatial associations ______ on the screen of PC now. (to display)

5. The spatial associations ___ on the screen of PC. (to display/tomorrow)

6. The spatial associations ________ on the screen of PC. (to display/ yesterday/ by 11 o’clock)

7. This distortion ___ by the cartographer on the screen of PC. (to correct)

8. This distortion _________by the cartographer on the screen of PC. (to correct/ now)

9. This distortion _____ by the cartographer on the screen of PC. (to correct/ yesterday/ by 2 o’clock)

10. The elevation contour lines ________ by the topographer. (to show)

11. The elevation contour lines ________ by the topographer. (to show/ yesterday/at 10 o’clock)

12. The elevation contour lines ________ by the topographer. (to show/ tomorrow/ by 10 o’clock)

Exercise 1. Read and translate the text.