Basic topographic mapping

transcript

Topographic Mapping

By: Edmund G. Millare BSED-SS

Types of Maps

• Climate Maps - give general information about the climate and precipitation (rain and snow) of a region. Cartographers, or mapmakers, use colors to show different climate or precipitation zones.

• Economic or Resource Maps - feature the major types of natural resources or economic activity in an area. Cartographers use symbols to show the locations of natural resources or economic activities. For example, wheat on a map of Maryland tells you that wheat is grown there.

• Physical Maps - illustrate the physical features of an area, such as the mountains, rivers and lakes. The water is usually shown in blue. Colors are used to show relief—differences in land elevations. Green is usually used at lower elevations, and orange or brown show higher elevations.

• Street Maps/Road Maps - street maps illustrate smaller areas such as towns and cities. People use street maps to find directions to a place they want to go. A road map shows the highways or interstates. These maps are also used to find directions.

• Political Maps - do not show physical features. Instead, they show state and national boundaries and capital and major cities. A capital city is usually marked with a star within a circle.

• Topographic Maps - include contour lines to show the shape and elevation of an area. Lines that are close together show steep terrain, and lines that are far apart show flat terrain. Many hikers use topographic maps, especially in areas where there are no roads with signs. Geologists depend on topographic maps to record the types of rocks. Engineers use topographic maps when they are planning roads, buildings, or other human–made structures.

Parts of Map

1. Scale: Scale is used to show that a certain distance on the map represents the actual distance on the earths surface. On a map, scale is represented using words (for example, one inch = 400 miles) or using a graphic (a line graph).

2. Title: What the map is about. The title is generally the biggest, darkest, most noticeable text on your map.

3. Legend or Key: Used for defining and understanding the symbols found on the map. It is usually in one of the corners of the map and is often enclosed by a box. It explains the meaning of the different sizes, shapes, and colors used in the map.

4. Symbols: The things on the map which stand for or represent real things on the earth’s surface. Symbols vary according to 2 categories: color and shape. For example: a star is often used to represent the capital city or yellow to represent a desert.

5. Compass: The compass shows which way is up on the map. Nearly all maps are printed so that north is towards the top of the page. This is shown by a compass rose using N, S, E, and W.

COMPASS ROSE

LEGEND and

Symbols

What is a Topographic Map?

In contrast to most maps, a topographic map

shows the shape of the Earth’s surface by using

contour lines.

Contours are imaginary lines

that join points of equal elevation

above or below sea level.

Let’s take a walk up a hill!

We’re now at an elevation of 100 meters.

Let’s keep going!

Now we’re at 200m.

Shall we march on?

We’ve made it to 300m!

On to the peak!

We’re on the peak, but what’s our elevation?

Any ideas?

Let’sadd contour lines for every 50 meters and see if that helps.

We know that we are above 350m, but less than 400m.

Let’s head down the hill, it’s getting late!

Now what’s our elevation?

If you said somewhere between 200m and 250m you are right!

Let’s try this again!

What’s our elevation now?

If you said 50m or just under, you’re right!

Let’s now look at the same hill, but the way we

might see it from an airplane!

Each color change represents a 50 meter increase.

Now, let’s try the same hike! Our elevation is 0 meters.

Now what is our elevation?

If you said more than 150 meters, but less than 200 meters your

right!

Let’s go a little higher.

Think you know our elevation now?

More than 300meters

But less than 350meters

If we were standing on the peak, what would be our

elevation?•More than 350 meters,

less than 400 meters

Let’s head down hill.

Know our elevation?

More than 100 meters,

less than 150 meters

What are contour lines?

• Contour lines are lines that connect points that are of the same elevation.

• They show the exact elevation, the shape of the land, and the steepness of the land’s slope.

• Contour lines never touch or cross. The elevation difference from one line to another

is called the contour interval. On the map portion below the contour interval is 20 ft.

20 ft elevation increase

20 ft elevation decrease

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The contour interval is usually printed on a topographic map.

• If the contour lines are far apart, then that indicates the land has a gentle slope (low slope).

• If the contour lines are close together, then that indicates that area has a steep slope.

Contours and Profiles

You can generate a profile of a landform from the contour lines on a topographic map.

Contours and Profiles

From a contour plotwe can draw anaxis line.

We can then drop lines straight downto a grid labeled withelevations to the correct value.

Connecting thepoints generatesa profile or cross-section ofthe map.

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Map Symbols

Topographic maps usually have a separate sheet with an explanation of map symbols. There is no room on the map for all the symbols

Sample page from USGS Topo Map Symbol Pamphlet

Map Symbols

Stream

Forest

Intermittent Stream

Secondary Highway

Houses

Basic topographic mapping

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