Representation of the Earth

   1. Representation of the Earth

   To have a more accurate knowledge of the earth and facilitate the travels, Men have tried to draw it with its continents, countries, cities, etc.

   For that reason, they have used the sphere or globe, maps and plans.

   2. The globes

   They are made of wood, glass, cardboard or other material. The continents and ocean are drawn on the surface. A globe is the most accurate representation of the earth.

   They have the advantage of representing the real earth's figure with great fidelity and give a clear overview.

   The biggest problem is that the features of the Earth are represented on a very small scale and if we want to have more details, the globe would have to be very big.

   3. The maps

   They represent the Earth's surface on a flat surface of paper or clothing.

   The study of maps is known as cartography.

   The advantage is that they are very manageable and we can represent the geographical facts in great detail.

   The problem is that the features of the earth are too deformed because they cannot represent the curvature of the Earth.

   4. Answer if the following sentences refer to the globe or the map:

It is a flat representation

They are made of wood or cardboard

It is the most accurate representation of the earth

They are very manageable

They show more details

    5. Geographic coordinate system

   We use them to indicate the position of any point on the earth's surface. They are latitude and longitude.

   - The latitude is the measurement of distance north or south of the Equator. It will be North or South latitude according to the corresponding hemisphere. The distance is measured in degrees and each one has a length of 111 kilometers.

   - The longitude is the distance from an earthly point to the Greenwich meridian (Prime meridian). Nowadays, The Greenwich Meridian runs through Greenwich in England. The Americans also use the Washington meridian and the Russians use the Pulkovo meridian. The longitude can be East or West.

   6. Indicate if the following sentences refer to the latitude or longitude:

It takes as reference the Equator

It takes as reference a meridian

It can be North or South

It can be East or West

Greenwich Meridian

One degree is 111 kilometers

Washington Meridian

   7. Map projection

   it is a method for developing or designing the earthly spherical surface on a plane.

   The principal methods are three:

   a) The cylindrical projection result from projecting a spherical earth's surface onto a cylinder that is tangent to the Equator.

   The map has small deformations along the Equator and big deformations in the polar zones.

   b) The conical projection results from projecting the features of the Earth on a cone.

   The deformations are small along the parallel and they increase as we move away from it.

   c) The elliptical projection, also known as Mollweide projection, is based on projecting the network of parallels and meridians on an ellipse.

   This method has few deformations of the Earth's surface.




   8. Answer with one these type of projection: cylindrical, conical or elliptical

It is projected onto an ellipse

The polar zones deform very much

It is projected onto a cone

It is called Mollweide

It is projected onto a cylinder

It is tangent to the Equator

It is tangent to a parallel

It produces few deformations

   9. Representation of land relief: the scale
   To represent the mountains of the crust, we use the contour lines and the lighting based on a shading of different colors. When the contour lines are close to each other, it means that the slope is steep. On the contrary, if the lines are separated, it indicates that the slope is small.
   We use the scales since we cannot represent the Earth in its real dimensions because the map would be immense. The scale is the relationship between the real dimensions of the Earth and the dimensions represented on the map. For Example: a scale of 1:2 000 000 means that every centimeter measured on the map is equal to 2 million centimeters.

   10. Indicate if these sentences are true or false:

The contour lines represent the land relief

If the line is close, the land is flat

Different colors are used

If the curves are separated, the land is sloping

We use scales to make maps

   11. Types of maps
a) According to scale, maps are classified as:
   - Geographical: when the scale is greater than 1:200 000
   - Topographic: when the scale is between 1:200 000 and 1:25 000
   - Plans: when the scale is less than 1:25 000. See the picture.
b) According the content, they are classified as:
   - Physical: they represent mountains, rivers, lakes, etc.
   - Humans: they represent the human population.
   - Economic: they represent the sources of wealth.
   - Political: they represent the division of states.

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®Arturo Ramo García.-Record of intellectual property of Teruel (Spain) No 141, of 29-IX-1999
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