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# Projections

Because the shape of the world is spherical, it is difficult to represent it on a plain paper. Cartographers use projections to make maps. Different map projections are made dots and lines.

## Mercator projections

The Mercator Projection was made by the Flemish geographer and cartographer Gerardus Mercator in 1569. It is a cylindrical map projection.
It has parallel latitude and longitude information. The land masses in the poles are exaggerated and therefore the figures are correct, but the areas are distorted.

## Conic projections

The conical projection system is placed on the earth of a cone shape and is reflected in points and lines. There is very little distortion between latitude lines. It has a high degree of accuracy in small areas. Used in road and weather maps.

## Gnomonic projections

Gnomonic projection is made of protruding points and lines. On a piece of paper touching a single point on the sphere is made by reflecting the dots and lines from the spheres. There is no distortion in the single point where the map is foreseen. Therefore, it is ideal for navigation. Specifies the straightest route when traveling from one point to another.

# Topographic Maps

Topographic maps are maps that show the valleys, hills and changes in altitudes and are used to show forests, rivers, roads. Uses points, lines and colors to show the earth’s surface elevations and shapes.

Contour lines Elevation on a topographic map is represented by a contour line. Elevation refers to the distance of a location above or below sea level. A contour line connects points of equal elevation. Because contour lines connect points of equal elevation, they never cross. If they did, it would mean that the point where they crossed had two different elevations, which would be impossible.

Contour intervals,  topographic maps use contour lines to show changes in elevation. The difference in elevation between two side-by-side contour lines is called the contour interval. The contour interval is dependent on the terrain

Index contours To aid in the interpretation of topographic maps, some contour lines are marked by numbers representing their elevations. These contour lines are called index contours, and they are used hand-in-hand with contour intervals to help determine elevation.

# Geologic Maps

The most useful tool for a geologist is a geological map. The geology map is used to show the distribution of the formations. Also a geological map shows fault lines and bedrock.

Using the information contained on a geologic map, combined with data from visible rock formations, geologists can infer how rocks might look below Earth’s surface. They can also gather information about geologic trends, based on the type and distribution of rock shown on the map.

Three-dimensional maps Topographic and geologic maps are two-dimensional models of Earth’s surface. Sometimes, scientists need to visualize Earth three-dimensionally. To do this, scientists often rely on computers to digitize features such as rivers, mountains, valleys, and hills.

## Map Legends

Most maps include both human-made and natural features located on Earth’s surface. These features are represented by symbols, such as black dotted lines for trails, solid red lines for highways, and small black squares and rectangles for buildings

## Map Scales

When using a map, you need to know how to measure distances. This is accomplished by using a map scale. A map scale is the ratio between distances on a map and actual distances on the surface of Earth. Normally, map scales are measured in SI, but as you will see on the map in the GeoLab, sometimes they are in measured in different units such as miles and inches. There are three types of map scales: verbal scales, graphic scales, and fractional scales.

# REFERENCE

Borrero B.,Hess F,S,.Hsu,J.,Kunze, G., Stephen A. Leslie ), Stephen LetroMichael MangaLen Sharp ( 2008 ) Glencoe Earth Science: Geology, the Environment, and the Universe, Student Edition (HS EARTH SCI GEO, ENV, UNIV) 1st Edition, Earth Science,

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