LAB Module 2: The Geographer’s Tools
Note: Please refer to the GETTING STARTED lab module to learn how to maneuver through and answer the lab questions using the Google Earth () component.
Students should know and understanding these terms:
|Absolute location||GIS||Relative location|
|Aerial photographs||Latitude||Remote sensing|
|Contour lines||Longitude||Satellite images|
|Coordinate systems||Map scale||Thematic maps|
|Geospatial technologies||Reference maps|
Lab Module Learning Objectives
After successfully completing this module, you should be able to do the following tasks:
· Use Latitude and longitude to find a location
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.
Lines of latitude, or parallels, divide the globe at the Equator, and run parallel in both the Northern and Southern Hemispheres. Locations in the Northern Hemisphere are denoted with an N (or a positive number), while locations in the Southern Hemisphere are denoted with an S (or a negative number). At the Equator, the parallel is 0°N or S, and increases to 90°N (or +90) at the North Pole, and 90°S (or-90) at the South Pole.
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.
Change your units to degrees, minute and seconds. (Refer to the GETTING STARTED module for direction on how to change latitude and longitude units). As a reminder, include your hemispheric designation (N/S, E/W) for each location.
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.
|Representative Fraction (RF)||1/12,000|
|Verbal||1 inch equals 1,000 feet|
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.
|1 m||100 cm|
|1 km||1000 m|
|1 km||100,000 cm|
|1 ft||12 in|
|1 mile||5,280 ft|
|1 mile||63,360 in|
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.
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.
Figure 2. Map with a 1:24,000 scale
|Map with a 1:24,000 scale. Notice the size and detail of Southport Island.|
Figure 3. Map with 1:62,500 scale
|Map with a 1: 62,500 scale. Notice the size and detail of Southport Island.|
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.
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.
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.
· 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).
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?
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 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.
Click Landsat Viewer. (Note: if the webpage does not open or takes too long to load, open the web browser outside of Google Earth by choosing the browser icon at the top left corner of the Google Earth Viewer.)
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.
Finally, type in your location (or the location provided by your instructor) into the search box and press the Enter (Return) key on your keyboard.
Question 40 Have there been any notable increases or decreases in vegetation? If so, where?
Condense and uncheck REMOTE SENSING. You have completed Lab Module 2.