Geography

· Explain the difference between large and small scale maps

· Calculate map scale

· Identify and describe the three types of maps

· Interpret contour maps

· Identify change in land use, or land cover, or both

INTRODUCTION

This lab module examines some of the fundamental concepts and tools geographers use to study the earth. Topics include latitude and longitude, absolute and relative location, geospatial technologies, map types and scale. While these topics may appear to be disparate, you will learn how they are inherently related. The modules start with four opening topics, or vignettes, which are found in the accompanying Google Earth file. These vignettes introduce basic concepts of the geographer’s tools. Some of the vignettes have animations, videos, or short articles that will provide another perspective or visual explanation for the topic at hand. After reading the vignette and associated links, answer the following questions. Please note that some links might take a while to download based on your Internet speed.

Question 1: What are three geographic technologies geographers use to study the Earth?

Question 2: In what state was the first topographic map (relief map using contour lines) issued in the United States?

Question 3: Why is the Equator the only parallel of latitude that is also a great circle?

Question 4: List five applications or uses for remote sensing technology.

Latitude and Longitude form a grid on the earth’s surface, enabling us to determine an absolute location for any given place or phenomenon.

Figure 1. Poles, latitude and longitude, and prime meridian

Lines of longitude, or meridians, run from pole to pole. Along the Prime Meridian, which runs through Greenwich, UK, the Earth is divided into Eastern and Western Hemispheres. Locations in the eastern hemisphere are denoted with an E (or a positive number), while locations in the western hemisphere are denoted with a W (or a negative number). Meridians increase at move toward 180°E (or +180) or 180°W (or -180).

Latitude and longitude are measured in degrees, minutes, and seconds. Like a clock, with one hour equaling 60 minutes, and one minute equaling 60 seconds, each degree of latitude and longitude can be divided into 60 minutes (60’) and each minute of latitude and longitude can be further subdivided into 60 seconds (60”). For example, the White House in Washington, DC is located at 38° 53’ 51” N, 77° 02’11”W. Latitude and longitude can also be measured in decimal degrees, or degrees and decimal minutes, which convert the minutes and/or seconds into decimal fractions. So for the White House, the absolute location in decimal degrees would be 38.897, -77.0365.

Question 5: What are the latitude and longitude coordinates for Location A?

Question 6: What are the latitude and longitude coordinates for Location A?

Question 7: Which of these locations – A or B - is closer to the Equator?

Question 8: By how many degrees (rounded to the nearest degree) is this location closer?

Question 9: Which of these locations is closer to the Prime Meridian?

Question 10: By how many degrees (rounded to the nearest degree) is this location closer?

Question 11: What are the latitude and longitude coordinates for Location C?

Question 12: Which location – A or C - is closer to the Equator?

Question 13: Which location – A or C – is closer to the Prime Meridian?

Scale

Scale is the ratio of the distance between two features on the map and the distance between the same two features on the ground. Maps should provide a scale to the user; typically, map scales are shown in the bottom margin of the map.

Scale is expressed in one of four ways: ratio, representative fraction, bar, and verbal. For example, 1:12,000 (ratio), 1/12,000 (representative fraction), 1 inch 1,000 feet (verbal) or as a scale bar illustrated below.

Scale Expression

Question 14: In what ways is the scale on this map expressed or presented?

As you zoom in or zoom out on the map, the scale of the image changes, even though the scale provided on the map does not change. Hence, when using maps in Google Earth, you cannot use the scale provided on the map. To calculate distance you need to use the ruler tool, which will give you an approximation of the distance.

· S = scale

· d = distance between two features on the map

· D = distance between two feature on the ground

Whether using the metric system or the British/Imperial system, make sure that you know the conversions between the units.

12

Metric

British/Imperial

To calculate the scale, divide d by D. But before we do this, both distances need to be in the same units. Currently d is in inches and D is in feet. We know there are 12 inches in a foot, so we can multiply D by 12 to convert the distance on the ground from feet to inches.

D = 16,000’ x 12” = 192,000”

Therefore, S = 8”/192,000”

We can then simplify S so that the numerator is a 1.

Thus, S = 1/24,000

This ratio can also be written as 1:24,000.

We need to convert distances into the same units. There are 63,360 inches in a mile. If we multiply 12 miles by 63,360 we can convert D into inches

D = 12” x 63,360” = 720,360”

Thus, S = 6”/720,260”

We can simplify S and we get a scale of 1/126,720 or 1:126,720

Notice that Examples 1 and 2 have different map scales. The map scale in Example 1, at 1:24,000, is larger than the map scale in Example 2, at 1:126,760. Large-scale maps are more “zoomed in” and therefore show more detail, but less area. Conversely, small scale maps are more “zoomed out” and therefore show more area, but less detail. Figures 2 and 3 illustrates larger and smaller map scales.

d = S x D

d = 1/100,000 x 5km = 5km/100,000

d = 0.00005km

d = 5cm

D = d/S

D = 5cm / 1/50,000 = 250,000cm = 2.5km

Question 15. Using Figure 4, we want to calculate the distance on the ground, in miles, between Mill Point and Oak Point. We measured 5 inches on the map itself, and know that the map scale is 1:63,360. Show your work.

Figure 4.Mill and Oak Points.

Question 16: What is the distance on a map in centimeters between two features if they are 7.6km apart on the ground and the map has a scale of 1:125,000? Show your work.

Google Earth does not provide scale as a ratio, representative fraction, or a verbal scale, but as a bar (graphic) scale. This is found in the lower left hand corner of the screen. Although it may seem counter intuitive, the smaller the distance shown on the scale bar, the larger the map scale.

Question 17: What is the distance, in feet, represented by the scale bar? ____________________________

Question 18:What is the distance, in feet, represented by the scale bar? ____________________________

Question 19: Which one has the smaller scale – Squirrel Island 1 or Squirrel Island 2?

Contours

Contours are lines that connect places of equal elevation. A contour interval (CI) is the elevation difference between two consecutive contour lines, and is commonly provided in the margin of a map. In Figure 5, the contour interval is 10 feet, meaning each consecutive contour line represents a 10 foot change in elevation. Index contours are typically labeled and are bolder than regular contour lines. In Figure 5, the index contours are every 50 feet (every 5 contour lines); index contours at 50, 100, and 150 feet are clearly visible.

There some rules regarding contour lines:

A

Cz

D

B

· Contour lines always form a closed polygon although on a smaller map contour lines might run off the margin (see contour line designated A on the map).

· Contour lines spaced closer together depict a steeper slope; whereas a wider spacing of contour lines depicts a gentler slope (see contour line designated B on the map).

Figure 5. Contours

· Contour lines might touch where there is a steep elevation change, like a steep slope or cliff; however, contour lines never cross unless the cliff face has an overhanging ledge (hidden contours are then depicted as dashed lines).

· Concentric, closed contours denote a hill or summit (see C on the map); whereas closed contours with hachure marks on the downslope side depicts a depression.

· Contour lines point upstream, creating a V-shaped pattern wherever they cross a river (see D on the map).

A USGS 7.5” map will appear, with two red squares near.Georgetown, ME. You may need to pan and/or zoom in or out to answer the following questions.

Question 21:What is the contour interval of this map?

Question 21: What is the highest elevation within the two squares?

Question 22: Within the right square, determine which direction (North, East, South, West) the river is flowing.

Question 23: Explain what contour rule helped you answer Question 22.

Question 24: Within these squares, where is the steepest slope located?

Question 25: Within these squares, where is the flattest area?

Question 26: As you move from left to right across the yellow line, is the elevation increasing or decreasing?

At the bottom of the screen is a cross section chart of the terrain over which the line is located. As you run the cursor along the line, the corresponding location along the cross section is identified. Additional information is located at the top of the graph area.

Question 27: As you move from the road intersection to the top of the hill, does the elevation continually increase?

Question 28: What is the length of the profile line (in feet)?

Question 29: What is the change in elevation of the line (the relief) from one end to the other (in feet)?

Question 30: Knowing that slope is the rise (relief of the line) divided by the run (distance of the line), compute the percent slope of the line. You must show your work to receive full credit.

Rise/Run *100 = ________ / _______*100 = ______________

Remote sensing

Remote sensing is the art and science of acquiring information about a feature or phenomenon without being in direct contact of that feature or phenomenon. In this part of the lab, you will explore land use and land cover change using satellite imagery. For the rest of this lab, you will be working with Landsat satellite imagery, which is considered the longest continuous global record of Earth’s surface.

Question 31: How long has Landsat been collecting data on Earth?

Question 32: Natural disasters like the Mount St. Helens eruption and urban growth in places like Las Vegas are two uses of Landsat data. Based on the video, name two additional physical geography topics – and their example locations – for which Landsat imagery has been used.

Question 33: How much does Landsat data cost?

In the ESRI web site, go to the top right hand corner in the ESRI website and click View larger. The default image should be Mount St. Helens, in Washington, USA. If it is not, type Mount St. Helens in the search box and press the Enter (Return) key on your keyboard. To zoom in or out, use any slider found in the top left-hand corner of an image area. Assume North is at the top of the images.

The images on the left (1975) and center (2000) panels are called false color composite images. They are displaying reflected infrared energy, which are wavelengths that are longer than visible light but shorter than micro waves. . Vegetation reflects a great amount of this energy, and as a result, appears as red in the images. The image to the far right is the change or difference between the 1975 and 2000 images. For a further interpretation of colors, see the legends found below the images.

Question 34: In which direction(s) was the 1980 eruption?

Question 35: How did you determine this from the remote sensing imagery?

Question 36: In which direction(s) has the majority of urban growth occurred between 1975 and 2000?

Question 37: What is the bright red (green in the change detection image) rectangle features, many found on the west side of Las Vegas?

Question 38: Is urbanization in this region linked more to increase in vegetation, or a decrease in vegetation?

Question 39: What is the diagonal strip running SW-NE through the city?

Question 40 Have there been any notable increases or decreases in vegetation? If so, where?