True Maps False Impressions Making Manipulating and

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ch01 qxd 6 1 06 1 16 PM Page 16, 16 Chapter 1 True Maps False Impressions Making Manipulating and Interpreting Maps. Questions 1 1 to 1 3 assume a scale of 1 25 000 Note that this scale is different from. those in either of the examples just given, 1 1 Suppose that City A is four centimeters away from City B on the map How. many centimeters apart are they on the surface of the earth. 1 2 How many kilometers apart are Cities A and B on the surface of the earth. 1 3 A bakery needs to supply bread to every store within a six kilometer radius How. many centimeters will this radius be when drawn on the map Hint First convert. 6 km to cm and then multiply by the representative fraction 1 25 000. 1 4 Which is the largest scale map,a 1 24 000 b 1 62 500 c 1 100 000 d 1 250 000. 1 5 Which of the following maps is larger scale, 1 6 Would your college campus appear larger on a map at a scale of 1 500 or 1 5 000. Scale is more than just a way of zooming in or out for a closer look or a broader. perspective When you change scales you can actually see a different spatial pro. cess at work The process you will investigate in Questions 1 7 to 1 9 involves whether. the northeastern U S population became more concentrated or more spread out. during the twentieth century,2006 John Wiley Sons Inc.
ch01 qxd 6 1 06 1 16 PM Page 17,Activity 1 Scale 17. Figure 1 11 shows each county s percentage of the northeast regional popula. tion for 1900 top and 2000 bottom at a relatively small scale of 1 12 000 000. At this scale you can see the whole northeastern section of the United States and. each county is fairly small We could call this a regional scale map. Figure 1 11 Regional scale map of population by county in the northeastern United States 1900. 2006 John Wiley Sons Inc,ch01 qxd 6 1 06 1 16 PM Page 18. 18 Chapter 1 True Maps False Impressions Making Manipulating and Interpreting Maps. 1 7 On the regional scale maps Figure 1 11 did the population become more spread. out people distributed more uniformly and evenly across counties or more con. centrated more people living in a few places from 1900 to 2000 Explain how you. interpreted the map pattern to reach this conclusion. Now look at Figure 1 12 which zooms in on the Baltimore Washington region. This is a larger scale map at 1 1 200 000 In fact it is exactly 10 times larger This. is a more local scale map Notice that the level of aggregation has stayed the same. as in Figure 1 11 It still shows the percentage of regional population by county. 1 8 On the local scale maps Figure 1 12 did the population of the Baltimore. Washington region become more spread out or more concentrated from 1900 to. 2000 Explain how you interpreted the map pattern to reach this conclusion. 2006 John Wiley Sons Inc,ch01 qxd 6 1 06 1 16 PM Page 19. Activity 1 Scale 19, Figure 1 12 Populations in Baltimore Washington region 1900 and 2000. 2006 John Wiley Sons Inc,ch01 qxd 6 1 06 1 16 PM Page 20.
20 Chapter 1 True Maps False Impressions Making Manipulating and Interpreting Maps. 1 9 Geographers are fascinated by the links between processes at different scales. The patterns of change you see in the regional scale maps Figure 1 11 are a func. tion of Americans moving from the countryside to cities How is this related to the. patterns of change you see at the local scale Figure 1 12. 2006 John Wiley Sons Inc,ch01 qxd 6 1 06 1 16 PM Page 21. Activity 2 Thematic Maps 21,Name Instructor,True Maps False Impressions Making. Manipulating and Interpreting Maps,ACTIVITY 2 THEMATIC MAPS. This activity involves looking at the distribution of African Americans in the United. States or Aboriginals in Canada using different types of thematic maps You will. use some of the functions of a geographic information system GIS to look at the. various maps and choose the most useful ones A GIS is a software package that. makes maps and allows the user to analyze spatial data A GIS is a powerful tool. used by utility companies city planners engineers cartographers environmental. scientists and many others You will be using the mapping capabilities of a GIS to. interactively change the maps on your computer screen. A To start your activity log onto the Human Geography in Action Web site. or insert your CD into your computer, B Select this chapter from the drop down list and then click on. Computerized Chapter Activities, C Click on Activity 2 Thematic maps USA or Canada according to your.
instructor s directions, D Students who chose Canada should first read the short background. article on the geography of the Aboriginal population in the window that. appears Following the background article Canadian students will find. the computer instructions and questions to answer and hand in for the. Canadian case study You can print these if you like Proceed with the. digital instructions for the Canadian version, E You will see the first of four types of thematic maps you will use to. evaluate the distribution of African Americans in the United States In the. right margin are the names for all of the maps The map displayed is. County Choropleth which classifies each county into one of four classes. and assigns a pattern as shown in the map legend Notice that this map. shows the percentage of African Americans per county not the actual. number Choropleth maps are usually used to show intensity such as. percentages rather than magnitude such as total numbers You will. later see maps that show magnitude such as the total number of. African Americans, If you wish you can zoom in on portions of the map to get a better. view of a smaller area you would then be looking at a larger scale map. Simply move the slider at the upper right toward the plus sign To. zoom back out slide it toward the minus sign The percentage enlarge. ment is shown in the box below Next to the percentage is a menu for. choosing low medium or high resolution You can move the map around. on the screen if you click and hold the mouse button on the red square in. the small map in the upper right and move the square around You also. 2006 John Wiley Sons Inc,ch01 qxd 6 1 06 1 16 PM Page 22. 22 Chapter 1 True Maps False Impressions Making Manipulating and Interpreting Maps. have a layer of boundaries of States and another of City Names that you. can click on or off for reference, 2 1 According to the County Choropleth where would you say most African.
Americans live in the United States, Based on the map approximately what percentage of African Americans would. you guess live in the dominant region No need to write an answer just think. about it Would you say the overwhelming majority Maybe two thirds Less than. In fact only about one half of all African Americans live in the South About. the same number live outside the South in large urban areas of the Northeast. Midwest and West, F Click on the County Circle icon in the right margin Now do you believe. the previous statement This map is called a graduated circle map A. graduated circle is a type of proportional symbol whose size varies with. the value for each county This graduated circle map shows magnitude. with each circle a different size depending on the total number of. African Americans per county, 2 2 Based on this map name four cities with the largest number of African American. residents Don t forget you can zoom in and also turn on City Names. 2 3 Now you see that the way in which data are presented on maps can greatly alter. your perception of the distribution of the information being mapped By using a. different type of thematic map and by presenting the data in absolute rather than. percentage terms the latter map s message changes even though both maps are based. on exactly the same data What are the false impressions created by the County. Choropleth and County Circle maps,2006 John Wiley Sons Inc. ch01 qxd 6 1 06 1 16 PM Page 23,Activity 2 Thematic Maps 23.
2 4 Zoom in on the New York City area What graphic or visual problems do you. see with the way the graduated circle map represents the African American popu. lation of the counties adjacent to New York City, G Click on the icon entitled County Dot Dot maps are another way to pre. sent the distribution of African Americans According to the legend each. dot represents 15 000 people Any county with fewer than 15 000. African Americans has no dots those with 15 000 to 29 999 get one dot. those with 30 000 to 44 999 get two dots and so on. 2 5 What is a drawback of using this kind of map to compare the number of African. Americans in different counties, H Change the threshold that sets the number of people per dot to 50 000. and then to 5 000 by clicking on the buttons with these resolutions. Toggle between the three dot resolutions to see the different impressions. they portray, 2 6 Which map emphasizes urban areas while deemphasizing the rural South Why. I The level of aggregation i e the size of the spatial unit of analysis is. also important to the pattern depicted on the map Click on the County. Choropleth map again to get a fresh image of it in your mind and then. click on State Choropleth This shows the same data but by state rather. than by county Note that as you move your mouse over each state you. see the state name and the percentage of African Americans included in. the state s total population, 2 7 What different impression of spatial pattern do you get from the state map as. compared to the county map,2006 John Wiley Sons Inc.
ch01 qxd 6 1 06 1 16 PM Page 24, 24 Chapter 1 True Maps False Impressions Making Manipulating and Interpreting Maps. J Experiment with the different Color Scheme options seen at the bottom. of the window Think about how the colors relate to the percentage of. African Americans, 2 8 Which color scheme if any does a poor job of portraying the percentage of. African Americans Why, K Restore the original color scheme Next you will interactively define your. own class limits using the graphic array to the left of the map This graph. shows the distribution of data on the x axis in this case the percentage of. African Americans for each state from low to high The y axis which. ranges from 0 to 50 states shows the states in rank order from highest to. lowest percentage of African Americans As you move your mouse over. the dots in the graph the state name and percentage of African. Americans appear Starting at the upper left you can see that the lowest. 13 states are between 0 and 2 2 percent the next 13 states are between. 2 2 and 6 8 percent and so on Cartographers use graphic arrays to help. in setting class break points that divide the data into natural classes or. groupings Look for vertical groupings that indicate a group of states with. similar percentages of African Americans and set your class limits in the. empty horizontal gaps, The vertical red bars show your class limits in this distribution You can select. a bar by clicking on the top triangle with your mouse Holding the mouse button. down on the triangle move it left or right to set new class limits The shading. patterns between the bars match those of the map When you move the bars the. break points in the boxes below change to reflect the new position These boxes. can also be edited Click in a break point box edit the value and hit the Enter. key You will use this interactive graphic array and or the editable boxes to make. your final map but we aren t quite there yet You will experiment with several other. options first, L As you just discovered changing break points between classes can alter.
the impression the map gives Buttons at the lower left use standard car. tographic rules for establishing break points known as Equal Frequency. and Equal Interval, Equal Frequency Divides the data distribution into classes with. equal numbers of states this is the default you,first looked at Click this button and look at the. histogram bar graph below the map to see the,number of states in each class. Equal Interval Divides the data distribution into classes inter. vals of equal size between the smallest and,largest numbers Click this button and look at the. break points on the graphic array the red vertical. 2006 John Wiley Sons Inc,ch01 qxd 6 1 06 1 16 PM Page 25.
Activity 2 Thematic Maps 25,lines to see that they are equally spaced The. boxes below the graphic array also list the break,point values and they too will be evenly spaced. between the minimum and maximum values, The default map uses the equal frequency settings Click back and forth. between the Equal Frequency and Equal Interval buttons to see their. effects on the maps, M Another way to customize a choropleth map is to change the number of. classes The initial map has only four classes You can change the number. of classes to 5 or 6 using the small window at the lower left Set the map. to 5 classes and click Equal Interval and then Equal Frequency Finally. set 6 classes and click Equal Interval and Equal Frequency From these. six distinct maps Equal Frequency with 4 5 or 6 classes and the same. for Equal Interval choose the map you consider to be the most mislead. ing i e it creates the most inaccurate impression of where African. Americans live You may consult the actual data values for each state in. Table 1 2 to compare actual values to perceived values from the map You. True Maps False Impressions Making Manipulating and Interpreting Maps ACTIVITY 1 SCALE Map scale is the ratio of the distance on the map to the distance on the ground where both are measured in the same units Scale can be represented in three different ways Representative Fraction The map distance to ground distance ratio is written

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