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OBJECTIVES 1. Define GIS. 2. Describe how a Geographic Information System (GIS) works 3. Use a GIS system to learn more about the surrounding geography of a community in South Dakota. 4. Use a GIS to write a report about geography and demographics for a selected community in South Dakota. |
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WHAT IS GIS AND WHAT DOES IT DO? (Cindy L. Piearson1, Mary O'Neill2 and Cheryl L. Reese3 ) GIS is an immensely powerful computer mapping system or in our case, an online mapping system. GIS stands for Geographic Information Systems. More and more people around the country and around the globe would like to plug into geographic, social, economic, political, and environmental information to answer practical questions in their lives. To explore geo-referenced digital information, electronic tools that are designed for acquiring, presenting, and interacting with information that links location with measured values are needed. One such tool is called a geographic information system, better known as GIS. It is a tool for managing information of any kind according to where it is located. Here are three examples of business that use GIS to impact your life on a daily basis.
GIS technology powers solutions for:
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HOW DOES GIS WORK? Desktop GIS represents the real world on a computer similar to the way maps represent the world on paper. Both GIS and paper maps convey information about places. However, desktop GIS has power and flexibility that paper maps lack. The scale of the map influences the size of what appears on it. With GIS, however, you can store and link huge amounts of information about the objects represented on maps. These objects are called features. Each map feature has a location, a representative shape, and a symbol that represents one or more of its characteristics. Because features on maps are organized according to relative location or position, maps are good for showing the relationships among feature locations.These relationships, called spatial relationships, are important because understanding them helps us solve problems. Maps use three basic shapes:
Shapes alone do not give you enough information, so maps use graphic symbols to help identify features and provide information about them. Most features can be represented as more than one shape. The scale of a map tells how the size of the map features compares with the size of the geographic objects they represent. Map scales vary from small-scale to large-scale. For example, on a small-scale map a city may be represented as a point (Figure 1). That same city would be represented as an area on a large-scale map (Figure 2). |
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Figure 1. (above)
Picture of a small-scale map shown in a GIS. Black
Figure 2. (above)
Large-scale map representing cities, roads, lakes |
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GIS 2 With desktop GIS, you are not limited to the amount of information you can get about what you see on the map. Desktop GIS stores all the information about map features in a GIS database and links the features on the map to the information about them. This means that you can access all the information about a feature by simply clicking on it. For example, in Figure 3 (shown below) a table is shown on the left (highlighted in yellow) and a window titled a 'View' (highlighted in blue) is shown on the right. 'Views' are made of 'themes'.
The attributes of a river might include:
Desktop GIS formats attributes in rows and columns and stores them as tables. Each column stores a different attribute and each row relates to a single feature. The link between map features and their attributes is the basic principle behind how a desktop GIS works and is the source of its power. Once the map features and attributes are linked, you can access the attributes for any map feature or locate any feature from its attributes in a table. GIS can also display features based on any attribute in the table. Because the link between features and attributes is a two-way relationship, changing an attribute in the table automatically results in a change on a map. Desktop GIS links sets of features and their attributes and manages them together in units called themes. A theme contains a set of related features, such as roads, streams, parcels, or wildlife habitat areas, along with the attributes for those features. For example, in Figure 3, the theme shown in the view include: (1) Brookings County Roads, (2) Brookings County Rivers and Streams and (3) Brookings County Landcover Use. |
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Figure 3. Window from a GIS that shows the 'View' area with 'Themes' shown on the right side of the picture. On the left side of the picture, a table is shown.This table contains data about the map. All the themes for a geographic area taken together make up a GIS database. The design of a GIS database is strong because it's flexible. You can add new themes to a GIS database or delete old ones; you can separate themes to create more themes, or combine themes if they have common characteristics. What you want to do with a GIS database, and what information you need, will determine the best design for you.
Figure 4. (above) Example of a query of a GIS database.
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WHAT DO YOU NEED TO KNOW ABOUT THE DATA? Geographic data refers to information about the earth's surface and the objects found on it. This information comes in three basic forms:
Data can be created or bought. For example, a GPS receiver can be used to identify sites in an agricultural field where weed data is collected. A table can be created in the GIS showing location as well as species and number of weeds present in the measured area. Alternatively, data can be purchased. In most cases, images are bought from satellite or aircraft companies that used cameras to collect images of the Earth's surface. |
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Contributions from Environmental Systems Research Institute Http://www.esri.com Author Information: 1 6th grade science teacher, Mickelson Middle School, Brookings, SD, 2 Research Associate, Engineering Resource Center, South Dakota State University, Brookings, SD 3 Research Associate, Plant Science Department, South Dakota State University, Brookings, SDGIS GIS QUESTIONS: 1. What does GIS mean? |
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USING GIS MAPS These tutorials are designed around different GIS maps and their uses. These maps are used to record, store, open, examine, and display geographic data. The next part of the tutorial is designed to demonstrate the usefulness of these maps. You will need an extra sheet of paper to answer the questions in each section of the tutorial. |
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YOUR HOMETOWN You may download and print questions here or use a seperate sheet of paper. 1. Begin by using your mouse to right click on the GIS map link. Select open in new window. GIS Map Page 2. Use the zoom tool
3. On the right side of the map select the layers: State Boundary, Cities and Towns, and County Boundaries. Make Cities and Towns the active layer as shown in Figure 1 on the right. You must unselect streams and rivers. 4. Select the information
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QUESTIONS 1. What is the longitude and Latitude? 2. What is the land area in sq. miles? 3. What is the water area in sq. miles? 4. What is the Pop100 or population? 5. What is the SD City ID number? 6. Questions 6-10 Choose another city and answer questions 1-5 again. (ex. our state capital Pierre, a school rival, or other town of interest). |
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YOUR COUNTY 1. In the layers bar select County Boundaries as the active layer as shown in figure 2. 2. Use the 3. Using different active layers answer questions 11-19. |
County Boundary as active layer. QUESTIONS 11. What is the area? 12. What is the Perimeter? 13. How many acres are in your county? 14. What is a landmark in your county? 15. What is the ID # of that landmark? 16. What is the name of a stream or river? 17. How long is it? 18. What is the Median (MD) Latitude and Longitude? 19. What is the pH level? |
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YOUR COUNTIES GEOGRAPHIC CHARACTERISTICS 1. For this section, under visible layers have cities and towns, roads, and county boundaries selected at all times. 2. Select Geology
as visible and as the active layer and refresh the map. Use the toggle
tool
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QUESTIONS 20. Use the legend or information tool to find out what is your county's geology? 21. What subregion watershed do you live in? 22. What is the soil drainage percentage where you live? 23. What area of the state has coal reserves? 24. What two types of coal are in the state? 25. What is the annual rainfall in your county? 26. Is there a grassland or park in your county? If so, what is it? If not, name a nearby grassland or county? 27. How many acres are in that grassland or park? |
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SD STATE GEOGRPAHIC CHARACTERISTICS 1. This section will require the interactive use of different layers for questions 28-35. 2. Remember the toggle
tool 3. This sections about the state of South Dakota
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QUESTIONS 28. View the map with only streams and rivers. How does the direction the water flows in Western SD compare with the direction the water flows in Eastern SD? 29. Which part of the state has Glacial Sediments? 30. How many geological regions are there in SD? 31. Name a river in the Early Wisconsin Glacial Sediments area. 32. The picture below shows the Continental Divide in North Eastern SD where water flows North instead of South. What Subregion Watershed starts here and goes North?
33. How does the soil drainage in western SD compare to the soil drainage in Eastern SD? 34. Which small part of the state has the highest average rainfall? What mountain range is located here? 35. Except for the Black Hills, describe the rainfall trend as you move from southeastern SD to northwestern SD. |
to
zoom in on your hometown.
tool
found on the left side of the map. Now click on your hometown. Information
should be displayed about your hometown.
Changing the visible layer allows different information to be seen. Changing
the active layer allows different information to be displayed.
to
display the legend.
