GIS Data Visualization and Presentation Intro GIS

1. GIS Data Visualization and PresentationIntro GIS

2. Purpose of a Map Map is a representation of the features that occur on the Earth. Maps allow us to accomplish a number of things, such as: 1. Visualize Information 2. Obtain the spatial orientation and relationships of our data 3. Present results of analysis

3. An Example from United States Population • A picture says a thousand words. That is certainly true when it comes to maps. For example, take a look at the following list of information: • What does the table tell us? • How about trying to answer the following questions: • Which parts of the US have larger populations? • Do areas of high populations appear to be grouped together? • Which states have the largest change in population? • Are the southern states growing more quickly than the northern states? • By just looking at the raw numbers it is virtually impossible to answer those questions. However, if we were to put the information into a GIS to make a map, we can better visualize what the data actually shows.

4. Visualizing US Data • Now that’s better. Here we can see three maps. The first map shows the population in 1990 of the US by county. The next map shows the population in 1999, and the final map shows the change in population between the population in 1990 and 1999. • This gives us a clearer picture of the data we just looked at.

5. Digital Cartography • Cartography is the art and science of creating a map. • Digital cartography creates maps using a computer. • Making the map is often the final stage in a GIS project. - If we make a poor map, people will not be able to appreciate all the hard work and effort that went into the GIS project. - Believe it or not, many GIS projects have not received further funding, not because the work was bad, but because the final map produced did not adequately demonstrate the good work that was performed.

6. Cartographic Elements • Border: part of the map that extends beyond the neatline. • Neat Line: the visual frame for that map that acts like a frame to set the map apart. • Text Information: text information is a very important part of the map that helps explain what the map is about. It typically includes: • Title: describes the general theme or purpose of the map • References: provides the reader with information about how the map was put together. This would include information such as the map author, the source of the map, projections or datums used. • Annotation: provides information about individual features on a map, such as the name of the states, the names of rivers, lakes, roads, or other features. • Date: provides information about when the map was created. • Map Figure: shows the primary figure of the map. This is the central theme of the map. • Inset: often shows another map, especially when the map cannot show all the features in one map space, due to the distance between them. For example, including Alaska and Hawaii along with the contiguous states. Another use of insets are to provide a frame of reference for a zoomed in portion of the map. For instance, an inset on our previous map could show North and South America with the United States highlighted, while the map figure would show the United States at a larger scale. • North Arrow/Graticule: used as a reference to provide the proper orientation of the map. Most maps are oriented with north at the top, but this does not always have to be the case. Similarly, the graticule ordinarily run in a north/south, east/west orientation. • Graticule: • Legend: provides a key to what the individual symbols on the map mean. This could indicate what the colors mean, or line symbols. • Scale: a visual expression of the relationship between ground units and the map units.

7. BORDER NEATLINE INSET MAP FIGURE INSET GRATICULE SCALE TITLE LEGEND REFERENCES

8. All maps should include the following Title Scale Legend Body of the Map North Arrow Cartographer Neatline Date of Production Projections Used Source Information Basic Map Elements

10. Basic Map Elements

11. Map Features and Placement - USGS

12. Symbolizing Map Data

13. Types of Maps • Topographic • Thematic Population Land use Temperature USGS Topographic Map

14. Types of Thematic Maps • Choropleth • area is colored to represent proportional values of the variable under study • Dot Density • each dot represents 500,000 people • Graduated Circle • displays the value of the variable under study as a different sized symbol

17. Classification Methods for Choropleth Maps • Natural Breaks: Natural breaks identify breakpoints between classes using a complex statistical formula that attempts to minimize the sum of the variance within each of the classes. This method will find groupings and patterns inherent within the data.

18. Classification of Choropleth Maps • Equal Interval: The equal interval method divides the range of attribute values into equal sized sub-ranges. Then the features are classified based on those sub-ranges.

19. Classification of Choropleth Maps • Quantile: Each class contains the same number of features.

20. Exploring classifications • You should visit the site: http://maps.esri.com/ESRI/mapobjects/tmap/tmap.htm • This site is created by ESRI and will allow you to select any US State and map the census values. You can select quantile or equal interval. Also, you can change the number of classes as well as the attribute to classify. • Go to the site and map your own State. What happens when you use: • Quantile with a small number of classes • Quantile with a large number of classes • Equal Interval with a small number of classes • Equal interval with a large number of classes

21. Consideration in Map Design • Before you create a map, you should ask four basic questions: • What is the motive for making the map? • Who will read the map? • Where will the map be used? • What data is available to make the map? • You need to judge your audience. If you are making maps for the general public, your map should reflect their level of understanding. This will be a much different type of map than one created for a geotechnical engineering firm. If you make a map that is too difficult to understand, or one that is too simplistic, your audience may not appreciate the information that you are trying to communicate. • Also, the motive is important. That is, are you trying to inform your audience, or persuade them? Each map may take a slightly different presentation form, depending upon the motivation. • Finally, a little bit of psychology might be in order as well. Think about the colors you choose. If you are attempting to present grave information, such as the impact of contaminants on a community, choose colors or symbols that would best reflect the mood of your map.

22. Basics of Design • Place the map elements correctly: cartographers should aim for harmony and clarity when making a map. Also, clutter on a map makes the map harder to understand. Here is an example of poor placement and good placement.

23. Basics of Design • The map on the right is poor balance. The map figure is crammed into the upper right part of the map. Also, the legend is in the upper left hand corner. • Text should be clear, correctly, and tersely worded: try to avoid writing a “mini novel” when placing text on a map. Text is important, but remember, the visualization of the map and information is critical. • Color balance is important: you want to make sure that you choose appropriate colors. That is, colors that make sense. If you are discussing income levels, perhaps you might want to try different shades of green, since people associate money with the color green. If you were going to map the number of murders in an area, you probably want to avoid pastel colors as these are often thought of as fun colors. • Lets take a look at some good and bad maps.

24. Good maps • There are lots of sites that allow you to see good maps. A few are listed below: • http://www.lib.utexas.edu/maps/index.html • http://www.esri.com/mapmuseum/index.html • http://nationalatlas.gov/printable.html

25. A bad map

26. Some Final Map Advice • Keep it simple • People can only observe about 7 different colors • Choose colors appropriately • Warm colors to communicate good news • Choose good symbols • Symbols can effect peoples views

27. Simultaneous Contrast (left)

29. Some Map Outputs

30. Some Map Outputs

31. Class Maps