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27 Ideas for Teaching With Topographic Maps

Image showing a portion of a topographic map

The USGS publishes approximately 57,000 different topographic maps covering the United States. Topographic maps show contour lines (elevation and landforms), hydrography (rivers, lakes, marshes), transportation (roads, trails, railroads, airports), vegetation, boundaries, survey markers, urban areas, buildings, and a variety of other features. These maps are most commonly published at the 1:24,000 scale (7.5 minute quadrangle), although many other map scales exist.

Topographic maps are a fantastic teaching resource for educators. They can be used in a variety of ways in the science, math, geography, and history curriculum, from elementary to college level. Use the following ideas as an aid in building educational lessons or to spark your own ideas for using topographic maps in the curriculum.


Topographic Maps: Download free, digital USGS topographic maps in a georeferenced PDF format through the USGS Store (Click on "Map Locator and Downloader"), or order paper copies of maps from the same site. Choose between the up-to-date "US Topo" maps, which are computer generated, and the historical, hand-made USGS topographic maps, which were produced until about 1992. The historical maps are sometimes easier to read and easier for students to work with. Both kinds of maps are available as free PDFs or as purchasable paper products. Teacher discounts are available for paper maps.

Topographic Map Symbols: Download a pdf version of the USGS Topographic Map Symbols sheet.

Aerial Photos and Satellite Images: (free digital downloads) Go to GloVis and select "Collection/Aerial" for air photography or "Collection/TerraLook" for satellite imagery (or you can play around with other options). Select an area, then click on "Add" (lower left) and "Send to Cart" at the bottom of the screen. You must be a registered user (free) to download scenes.

Additional Resources: USGS Resources for Working with Topographic Maps, Map Scales, Map Margins (pdf), Coordinate Systems, Longitude & Latitude, UTM Coordinates, Map Adventures (grades K-3), What Do Maps Show? (grades 5-8), Exploring Maps (grades 7-12), Map Projections Poster (free hard copy from the USGS Store).

USGS Education Map Catalog: Browse a selection of USGS maps that are popular with educators by going to the USGS Store and clicking on "Education Products".

Products in pdf format require Adobe Acrobat Reader.

1. Coordinate Systems

Grade Levels: Secondary, University
Time Required: 1-3 hours
Materials Required: Topographic map, GPS receiver, metal dividers or plastic grid for interpolation

Divide students into teams. Ask each team of students to determine the latitude and longitude of the school building or campus to the nearest second using a USGS 1:24,000-scale topographic map. Draw a 2.5-minute grid on the interior of the map using 2.5-minute tic marks on the margin of the map as a guide for interpolating the coordinates. Discuss the process of interpolation. Write answers from all teams on the board. Discuss the need for accuracy. Use a 1:100,000 and a 1:250,000-scale map of the same area and discuss the difficulty of determining position depending on the map scale.

Latitude and longitude are in base 60. Each degree contains 60 minutes. Each minute contains 60 seconds. Use the base 60 hours-minutes-seconds concepts with time to help them understand this. Transfer discussion to base 60 with latitude-longitude degrees-minutes-seconds, and the fact that in latitude-longitude, degrees refers to distance, not heat energy, and minutes and seconds refer to distance as well, not time.

2. Global Positioning Systems

Grade Levels: Elementary, Secondary, University
Time Required: 1-3 hours
Materials Required: Topographic map, GPS receivers

Interpret the latitude and longitude location of your school using Idea #1. Divide into teams, go outside and record positions with a GPS receiver. Stay out at least 10 minutes for the most accurate averaging. Go back to the classroom. Compare your readings from the GPS receivers to the reading that each team interpolated from the topographic map. Which team was closest to the coordinates given by the GPS unit?

What coordinate system does your GPS unit use?

Repeat the above using the Universal Transverse Mercator (UTM) coordinate system. UTM coordinates are drawn on USGS maps in blue tic marks or a black 1,000 meter grid. Compare the convenience of units expressed in meters with UTM versus those expressed in degrees, minutes, and seconds (with lat/long). Discuss the accuracy of your GPS unit.

Discussion: Oftentimes the students will be too willing to discard their own interpolations from the topographic map and willing to accept a high-tech device, despite its accuracy limitations. These limitations include the inherent error in low-end GPS units, readings made near buildings or under trees, the limited availability of satellites at certain times of the day, and more. Many times, the students' interpolations will be more accurate, particularly with the Z reading (elevation). Discuss why this is so and the importance of understanding topographic maps and GPS.

3. Datums

Grade Levels: Secondary, University
Time Required: 2 hours to 1 day
Materials Required: 1:24,000 scale topographic map, GPS receiver

What datum is your GPS receiver set for? Chances are good that the default datum is WGS84 (World Geodetic System 1984) or NAD83 (North American Datum 1983). In the United States, WGS84 and NAD83are essentially identical. Now look at your topographic map. What datum does it use? Is it the same as your GPS receiver? What's the difference between the North American Datums of 1927 (NAD27) and 1983 (NAD83)? Is there information on the map about that difference? If the topographic map and the GPS receiver are using different datums, what problems might that cause? How can you work around those problems?

What is the date of your topographic map? If it was published after 1983, there should be a little dashed cross offset by about 3 millimeters from each of the four corners of the map. What is it?

These resources might be helpful:
Map Margins (pdf)
Datum Shifts (pdf)

4. Locating Benchmarks - Surveying

Grade Levels: Secondary, University
Time Required: 2 hours to 1 day
Materials Required: Topographic map, benchmark (optional)

Discuss benchmarks. Why are they important in mapping? Benchmarks and surveying are critical for making accurate maps that incorporate latitude (x), longitude (y), and elevation (z). Discuss why people demand accuracy in mapping, including a discussion on the uses of maps, and which data users require the most accuracy. Point out that the requirements of someone laying pipelines as opposed to someone locating climatic zones are quite different. If possible, obtain a benchmark from a surveying company or catalog and show the class what these markers look like.

With the aid of a topographic map symbols sheet, ask students to find as many benchmarks on the map as they can. What features are the benchmarks on? Discuss why certain features such as mountain peaks and railroad track sidings are better locations for mounting benchmarks than others. Discuss the permanent versus transitory nature of these features and the possible results of mounting the benchmark in sand or in a tree. Discuss triangulation and leveling techniques. If possible, go on a field trip and try to find one or more of the benchmarks the students have found on the topographic map. Be aware of safety considerations when finding benchmarks. Many are on busy intersections or along railroad tracks.

Look at photographs of USGS topographers working with benchmarks and triangulation stations.

5. Geographic Coordinate System - Convergence

Grade Levels: Secondary, University
Time Required: 1 hour
Materials Required: Topographic maps, globe

Illustrate how lines of longitude converge from the equator to the poles. Illustrate the concept first on a globe. Next, show topographic maps from the northern part of the United States (North Dakota, for example) versus maps from the southern part of the country (Texas or Hawaii, for example). Why are the maps in North Dakota narrower in the east-west direction than those in Texas and Hawaii? Measure the differences. What is the distance between the 7.5-minute lines of longitude? Calculate how far it is between each minute of longitude, and then calculate how far it is between each degree of longitude. Measure on several different maps the distance between the lines of latitude. Ask the students why the latitude lines do not converge, and illustrate it on the globe.

6. Comparing Coordinate Systems

Grade Levels: Secondary, University
Time Required: 1-3 hours
Materials Required: Topographic map, USGS UTM Fact Sheet, a map showing state plane coordinates

Discuss how locations are measured on a piece of graph paper in geometry with the Cartesian coordinate system. Discuss why places on the Earth need to be located and measured according to a coordinate system as well. Three commonly used coordinate systems are latitude / longitude (the geographic coordinate system), the Universal Transverse Mercator (UTM) system, and the State Plane Coordinate System. All three of these coordinate systems are shown on USGS topographic maps (Map Margins). Ask the students to determine where the origin point is for each of the coordinate systems in use. Pair the USGS map with a state highway map or other state-based maps, county maps, or parcel maps that are in state plane coordinates. Ask why map projections are used. Ask about the relationship between map projections and coordinate systems. Discuss why different coordinate systems are used for different purposes. Discuss which data users would prefer one system over another, including mention of local government needs versus global needs. When does coordinate system have an advantage over another?

These resources might be helpful:
Map Projection comparisons
Teaching About and Using Coordinate Systems

7. Precision of Coordinates

Grade Levels: Secondary
Time Required: 1-2 hours
Materials Required: Topographic map

Discuss the precision of latitude and longitude readings off of a USGS topographic map. As an analogy, start by asking why hours have to be divided into minutes and seconds for increased precision. If two people were to meet after school at 4:00, and if one showed up at 3:58 while the other arrived at 4:02, the time difference would not be that important. We understand that we don't mean "exactly" at 4:00, but rather, around but reasonably close to 4:00. However, if you are launching a spacecraft, it is critical that you state that the launch will be precisely at 4:00.0355. Therefore, some events are scheduled at approximate times, but others need greater precision. Similarly, with locations on the Earth, sometimes an approximate location will do, such as "in front of the library." However, if you were installing high-speed Internet lines in front of the library, you would need to know precisely where to dig and install the lines. You would need more than degrees of latitude and longitude. Up to 60 miles may separate a degree of latitude or longitude. For increased precision, you would need readings down to the tenths of a second of latitude and longitude of its location. This is why people have divided degrees of latitude and longitude into minutes, and minutes into seconds.

8. Absolute versus Relative Location

Grade Levels: Secondary
Time Required: 1 hour
Materials Required: Topographic map

Discuss the difference between absolute location and relative location. What is the difference between "42 degrees 7 minutes and 31 seconds north latitude, 101 degrees 15 minutes and 44 seconds west longitude" and the phrase "northeast of Pleasant Grove"? When is absolute location important, and when is relative location important? Can you think of instances where they are both important? Which one does GPS measure? Which one(s) can you determine with a USGS topographic map?

9. Map Projections

Grade Levels: Secondary, University
Time Required: 1-3 hours
Materials Required: Topographic map, globe, USGS Map Projections poster (order free printed poster from USGS Store, $5 handling fee per total order)

Ask students to examine the map projection of a chosen USGS topographic map versus other maps. Show that each map is drawn according to a specific map projection. Discuss the advantage and disadvantage of different map projections. Why do Greenland and Canada look so large on a Mercator projection? You can use low-tech tools for illustration such as peeling an orange and trying to flatten out the peel on a flat surface. You can take advantage of high-tech tools such as a Geographic Information System (GIS) as follows. Draw a circle on the map of the Earth, and then change the projection, observing how it becomes distorted with different projections. Determine how and why the distance from Honolulu to Los Angeles varies, and how the angle with the equator varies. Illustrate with a globe and topographic maps. Discuss why the process of drawing the earth on a two dimensional piece of paper causes distortion in distance, direction, area, and angles.

Use the USGS poster map projections, as well as cartography texts to illustrate how distance, direction, angle, or area have to be distorted. When is it best to distort distance/direction/angle, or angle? If you had to choose 3 of the 4 attributes to keep accurate, what would they be?

Illustrate how choosing the map projection depends on the application. Illustrate how the projection of the map is more evident on a small-scale than on a large-scale map.

10. The History of Cartography

Grade Levels: Secondary, University
Time Required: 1-4 hours
Materials Required: Topographic map, other maps, USGS Exploring Maps Teacher Packet

Examine how maps were made in the past and the present. Obtain some negatives and scribing materials from a film or drafting company. Obtain a scribing instrument; a sharp nail or compass end will suffice. Pencil in some contour lines on the film and have students try to follow them with the scribing instrument. Alternatively, use pencils and tracing paper laid on top of USGS topographic maps. Discuss the fact that most topographic maps were prepared using manual scribing instruments and tracing. Discuss why film was used rather than paper: Film does not shrink or swell as much as paper with changes in temperature and humidity, thus preserving the National Map Accuracy Standards.

Use the USGS Teachers Packet "Exploring Maps." This packet contains two posters illustrating historical maps back to the Babylonians, through the Middle Ages, to present-day maps.

Illustrate with samples from the Library of Congress Map Collections.

11. Modern Cartography

Grade Levels: Secondary, University
Time Required: 1-3 hours
Materials Required: Topographic map, GIS software (optional)

Discuss Geographic Information Systems (GIS) and the capability of drawing all points, lines, and areas on the computer. Ask the students to describe the advantages of making maps on the computer versus by hand. Advantages include the ability to easily change the symbology, projection, scale, and then to have the map layers available for analysis in a GIS.

Visit Web sites running Internet map server software, where students can construct a map with a Web browser. The National Map Viewer is a good option.

12. Aerial Photo Interpretation

Grade Levels: Secondary, University
Time Required: 1-4 hours
Materials Required: Topographic map, USGS or other aerial photographs

Obtain an aerial photograph of an area from the USGS (use GloVis and select the "Aerial" collection option. Select an area on the map, then click "Add" and "Download" at the bottom of the page for free digital downloads) and also a USGS topographic map (use the USGS Store and click on "Map Locator") covering the same area. Ask students how they can identify a stadium, lake, golf course, school, office building, hospital, church, stream, mountain, and other features on an aerial photograph. The world is more complex than is at first realized. A school might have an athletic track, but what about schools in a dense urban area? Do they always have a track? Some schools might have a characteristic "pull out" drive for drop-offs, but does your school have one?

Ask students to identify the time of year that the photograph was taken. What are the clues? Do the leaves on the trees provide any hints? Ask students to identify the time of day the photograph was taken. What are the clues? What does the presence or absence of vehicles in the school parking lot tell you about the day of the week and the time of day? What is the best time to take a photograph if you are going to make a map from the photograph? Near solar noon is best to minimize shadow. Near the summer solstice is best also to minimize shadow, except in heavily timbered areas, when "leaf-off" times are best in March and November.

13. Analysis of Stereo Aerial Photographs

Grade Levels: Secondary
Time Required: 1-4 hours
Materials Required: Topographic map, USGS or other aerial photographs, stereoscope

Discuss the need to see the world in three dimensions for creating contour lines. Show "magic eye" images. Can the students see them in three dimensions? Obtain a stereo viewer and obtain stereo aerial pairs. Hubbard Scientific is one publisher of these in print form. There are also many stereo pairs on the web. If students have difficulty, tape the photographs on the table in the correct overlap position.

14. Creating Maps from Aerial Photographs

Grade Levels: Secondary
Time Required: 1-3 hours
Materials Required: Topographic map, other types of thematic maps, aerial photographs

Print a USGS aerial photograph of your school or other location (use GloVis and select the "Aerial" collection option. Select an area on the map, then click "Add" and "Download" at the bottom of the page for free digital downloads). Put a sheet of tracing paper over the photograph and tape it down. On the tracing paper, decide which features you will categorize and then map. These can include streets, sidewalk, the school building, trees, streams, the playground, the track, the flagpole, and other features. Decide the color and symbology that you will use to draw each feature type. How should each feature be mapped such that the map doesn't become too complicated or cluttered? Use the USGS topographic map symbols sheet as a guideline. Make maps that include all elements of "TODALSIGS"--Title, Author, Date, Author, Legend, Scale, Index, Grid, Source. How can students decide which features should be mapped? Discuss the reason why the real world needs to be simplified to make a map. For every theme that is drawn on a map, there are themes that are omitted (for example, soils). How can you determine the scale of your map? Go outside and pace off a feature, such as one side of the school building, and compare it to the distance on your map. Use the two numbers to determine the scale factor.

15. Analyzing Physical Features on Topographic Maps

Grade Levels: Secondary, University
Time Required: Expandable from 1 hour to several weeks
Materials Required: Topographic maps at a variety of scales

Visit an interactive website that shows topographic maps that illustrate geographic features such as eskers, drumlins, glaciers, playas, canyons, mesas, sand dunes, marshes, floodplains, volcanoes, alluvial fans, lava beds, karst, and so on. How are these features identifiable on topographic maps? What are the sizes of each of these features? What is the most suitable scale with which to examine the entire physical feature? What is the national or regional pattern of these physical features? How do physical features affect population settlement amount and patterns?

16. Looking at Streams and Rivers on Topographic Maps

Grade Levels: Secondary, University
Time Required: 1-3 hours
Materials Required: One or more topographic maps showing long streams and/or rivers

Look at a stream or river on a topographic map, preferably one that crosses the length or width of the map. In what direction does it flow? How do you know? Estimate the elevation of the river where it enters the map and where it exits the map. What is the approximate distance that the river flows on the map? Gradient is expressed as the vertical distance divided by horizontal distance. It may also be expressed as a percentage. What is the gradient of the river on the map? Would you expect a river's gradient to be greater near its source or near its mouth?

Look up real-time discharge for major streams and rivers on the USGS surface water Web site. at a wide river like the Mississippi on a topographic map. Assign it an arbitrary depth. What is the cross-section area of the river at a particular point (width x depth). Assign an arbitrary velocity like 5 feet per second. What is the river's discharge?(velocity x width x depth). Which is the most important factor in determining how much material is eroded and transported by a river - gradient or discharge?

This resource might be helpful:
Streamer from The National Map

17. Analyzing Change on Topographic Maps

Grade Levels: Elementary, Secondary, University
Time Required: Expandable from 1 hour to 1 week
Materials Required: Historical topographic maps and US Topo maps

You can freely download the entire historical suite of topographic maps for most locations in the United States through the Map Locator and Downloader on the USGS Store. Download US Topo maps at the same site.

Ask students how frequently maps of the Moon and Mars need to be updated. The answer: not very often! Maps of the Earth, by contrast, are often woefully out of date as soon as they're published. The Earth is a dynamic planet -- not only do we have volcanoes, landslides, earthquakes, floods, erosion, and other forces shaping the landscape, we have over 6 billion humans constructing buildings, canals, reservoirs, transportation systems, and otherwise affecting the surface of the planet.

Obtain historical topographic maps and compare them to the current (US Topo) editions for the same areas. Try to get them for your location. Look at the oldest map. What place names were used on the landscape and what is their origin? What names are no longer used today, and what new names exist? Why is your community located where it is? Where did your community begin, in which direction(s) did it expand, and why? Will it grow in the future, and how? What will your community look like on a map made ten years from now? Fifty years from now? What was the historic land use in a given region and how has it changed over the decades? What influence did physical features such as rivers and mountains have on the development of communities and regions? What influence did early roads, and later freeways, have on the development of cities? Why did some areas of cities develop as industrial, commercial, or residential? How have city neighborhoods changed over time? How do such forces as tourism, mining, and agriculture shape the land use as depicted on maps?

Discuss physical changes versus human-caused change. Examples of maps with physical changes include Earthquake Lake Montana, South Pass Louisiana, and Mt St Helens, Washington. Examples of maps with human-caused change include any map containing a reservoir or urban area. Look at the Map Mysteries lessons for more ideas.

This resource might be helpful:
USGS Geographic Names Information System (click on "Search Domestic Names")

18. Analysis of Impact of Public Land Survey System (PLSS) on the American Landscape

Grade Levels: Secondary, University
Time Required: 1-3 hours
Materials Required: Topographic maps of PLSS and non-PLSS states; map showing PLSS states

The Public Land Survey System (PLSS) is a way of subdividing and describing land in the United States. Discuss the 1785 Ordnance Act, signed into law by President Jefferson, that provided for this systematic survey and monumentalization of public domain lands. Obtain the Public Land Surveys map (purchase paper map or download PDF) from the USGS that shows the spread of the township and range system for dividing up land for settlement, beginning in Ohio and moving west. Roads in these states were often laid out running due north, south, east, and west. States that were settled before this Act was signed display a "metes and bounds" road network, where the roads run in a variety of directions, but rarely due north, south, east, or west. The Principal Meridians and Base Lines map is a nice supplement.

Discuss why Texas has no PLSS (it was a separate country for a period of time). What is the impact of this system on the rural landscape? Compare the human-built landscape in Virginia - - roads and boundaries - - versus the "rectangular" landscape in Kansas. What is the impact of this system on the urban landscape? Show maps of cities in PLSS states versus cities in non-PLSS states. Note, for example, the regular grid in the Phoenix street pattern versus the irregular pattern of streets in Atlanta. Emphasize how an act from 1785 continues to affect the routes we take to get to school every day! Did you travel on a section-line road to reach your school today? Compare the metes-and-bounds and PLSS systems versus the long lot system of the lower Mississippi River floodplain. Why and how did the long lot system develop?

19. Creating Profiles

Grade Levels: Secondary, University
Time Required: 2-4 hours
Materials Required: Topographic map, rulers

Draw several lines, called transects, across a USGS topographic map. Create cross-sections (profiles) along these transects, using the contour lines to determine the elevation at each position along the transect. Where is the topography steepest? Flattest? Why?

What forces are most active on the landscape in this area? Landslides? Floods? Erosion? Tectonism? Coastal storms? What forces were most active in the past? Glaciation? Were the past forces the same as today's forces?

Compute the slope both in percent and in degrees. Have students plan a railroad and a road from point A to point B through a mountainous region. Give students a constraint of 8% for the maximum road grade and 2% for the maximum railroad grade. Compare students' routes. Show map with railroad on it in another area, and have students compare the number of twists and turns, and calculate the total distance, between roads and railroads. Why do roads and railroads have different criteria for construction?

20. Analysis of Scale

Grade Levels: Elementary, Secondary, University
Time Required: 1-5 hours
Materials Required: Topographic maps at different scales (download free through the USGS Store Map Locator & Downloader)

Map scale is the relationship between distance on the map and distance on the ground and is usually given as a fraction or a ratio -- 1/10,000 or 1:10,000, for example -- meaning that one unit of measurement on the map represents 10,000 of the same units on the ground. Examine the differences in maps with different scales. Obtain different USGS maps of the same area. How large is your town on a 1:24,000-scale versus a 1:100,000-scale versus a 1:250,000- scale versus a 1:500,000-scale state base map? What accounts for this difference? What is the "optimal" scale for a map? Does it not depend on what it will be used for, and who will be using it?

What would a 1:1 scale map of your classroom look like? How big would it be? Would changing the scale make the map more user-friendly? Have students draw a map of the classroom on a piece of paper, then calculate the map's approximate scale. Conversely, have students draw a map at a specific scale that you assign.

Ask students if any of them have flown in an airplane. Discuss how the size of the visible area changes as the airplane climbs higher in altitude. This concept is further explored in the USGS Map Adventures for K-3 teachers.

Discuss the rather confusing concept of small-scale maps versus large-scale maps. A large scale map (for example, 1:24,000) is a larger number, or fraction, than a small scale map (such as 1:100,000) and shows a larger amount of detail. A small scale map shows a larger area but a smaller amount of detail. Compare this to more commonly used fractions. Is 1/10 of a pizza larger or smaller than 1/100 of a pizza? 1/10 is larger, and corresponds to a larger-scale map. A globe might represent the ultimate small scale map.

Discuss a trip from your city to another city that is several thousand kilometers away. Start by using a globe. When would you need a map at a large scale versus a small scale? You might need a small scale map to travel from your city to the other city, but then when you reach the other city, you need a large scale map to reach the block of your final destination within that city. This can also be illustrated by using a Web site with maps that have a graduated zoom function, like Google Maps or Yahoo Maps.

21. Analyzing Cultural Features on Topographic Maps

Grade Levels: Elementary, Secondary, University
Time Required: Expandable from 1 hour to several weeks
Materials Required: 1:24,000-scale topographic maps from a variety of areas, both urban and rural

What are the major commercial activities of the area shown on the selected topographic map? How are these activities reflected in the cultural, or human-built, features on the map?

Do people want to move to this area? Why? Is this a fast or slow-growing, or declining, area, and why? What forces act to limit or promote growth? Are the forces local, regional, national, or international in scale?

Why are certain land uses concentrated in certain areas? For example, what kind of buildings are near railroad tracks? Near stadiums? Near universities? Near interstate highways? Why?

22. Analyzing Place Names on Topographic Maps

Grade Levels: Elementary, Secondary, University
Time Required: Expandable from 1 hour to several weeks
Materials Required: 1:24,000-scale topographic maps from a variety of areas, both urban and rural

How do natural and cultural features get their names? What organization in each country accepts the names as "valid"? Examine the web site for the U.S. Board on Geographic Names for their procedures and history. Can names ever be changed? How?

What origin and nationality do the place names on your chosen USGS topographic map have? Compare the names to the names on another topographic map. What do you know about the people and events that the names depict? How old are the names on your map?

Look up the names on your map on the USGS Geographic Names Information System, a database containing over 2 million names on USGS topographic maps. Study books on toponyms (place names) like Names on the Land by George Stewart.

23. Construct 3D Models

Grade Levels: Elementary, Secondary, University
Time Required: 1-3 hours
Materials Required: Topographic map, plaster of Paris or other modeling material, water, tray OR Topographic map and 7-8 clear plastic salad containers, pie covers, or similar items

Construct plaster models of areas on topographic maps. Flood one inch, draw a contour line in marker, flood one more inch, draw another line, etc. Remove water, look at lines from above, to illustrate the concept of contour lines.

Alternatively, use clear salad trays from food stores. Trace one contour line on each tray. When completed, you will have a see-through 3D model of your landscape. See our complete instructions for how to construct a Topo Salad Tray model.

24. Analysis of Urbanization Over Time

Grade Levels: Elementary, Secondary, University
Time Required: 1-5 hours
Materials Required: Topographic maps of an urban area at 1:24,000 and 1:100,000 scale

Using USGS topographic maps of metropolitan areas, examine the urban area. Examine older versus newer urbanization. How do you know which is older? What are the differences in the street pattern, and why? Discuss how and why the chosen urban area first began, and how and why it spread. In which direction(s) is it growing, and why? Was there a river or other physical feature that helped the urban area get its start?

Why is older urbanization usually along straight streets and with smaller homes, versus newer urbanization? Discuss popular culture and consumer preferences.

How much urbanization is occurring in your selected city? Is it more or less than other cities of comparable size? Why? What local, regional, national, and international forces are acting on the city to make it change?

25. Create Aspect Maps

Grade Levels: Secondary, University
Time Required: 1-3 hours
Materials Required: Topographic map, sheets of blank poster paper

Aspect refers to the direction (north, east, south, west) that the slope faces. Create aspect maps by examining contour lines on USGS topographic maps. Discuss who would be interested in the direction that slopes face.

Compare the vegetation on north-facing versus south-facing slopes. What influence does aspect have on soil moisture, plants, and animal habitat? What aspects are ski areas usually built on? Discuss microclimates of slopes. Why are ski areas usually located on north-facing slopes? Where would ski areas be located in the southern hemisphere? Discuss earth-sun relationships.

26. Analysis of Humans and Hydrography

Grade Levels: Secondary, University
Time Required: 1-3 hours
Materials Required: Topographic map, GPS receiver, metal dividers for interpolation (optional)

Discuss floodplains, rivers, and settlement. How do rivers both encourage (with trade and traffic) and discourage (with flooding) settlement? Why does one bank of a large river aid the growth of a large city, while the other bank is sparsely populated? This might occur if one bank is higher and flood-free, and the other is historically flood-prone.

One example is Omaha, Nebraska on the high west bank of the Missouri River, versus Council Bluffs, Iowa on the flood-prone east bank. Omaha grew faster than Council Bluffs and remains the primary city in the region to this day. What is the elevation of both of your selected banks? Discuss the importance of a city site to be on a flood-free site, higher than the floodplain.

27. Site versus Situation

Grade Levels: Secondary, University
Time Required: 1-3 hours
Materials Required: Topographic map of New Orleans West and other locations

"Site" refers to the physical attributes of a location, such as soil, drainage, climate, and so on. "Situation" refers to the advantages and disadvantages of one location over another location, considering trade routes, transportation, and other regional and national and international connections.

Discuss site versus situation with USGS topographic maps at different scales.

Examine the New Orleans West, Louisiana 1:24,000-scale map. Estimate the amount of land below sea level. Which areas were flooded by Hurricane Katrina in 2005? Discuss the sustainability of draining of the land for a city site on a river delta. Discuss site versus situation here and elsewhere. New Orleans is a poor site (prone to flooding) but has a good situation (near the mouth of a large river). Discuss the impact of global sea level rise on New Orleans. Discuss another location that is a good site but a poor situation (for example, a well-drained location in the middle of a plain, far from an overland route or river).

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