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GIS Data Visualization and Presentation Intro GIS


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 ... – PowerPoint PPT presentation

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Title: GIS Data Visualization and Presentation Intro GIS

GIS Data Visualization and PresentationIntro
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

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
  • What does the table tell us?
  • How about trying to answer the following
  • Which parts of the US have larger populations?
  • Do areas of high populations appear to be grouped
  • Which states have the largest change in
  • 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.

Visualizing US Data
  • Now thats 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
  • This gives us a clearer picture of the data we
    just looked at.

Digital Cartography
  • Cartography is the art and science of creating a
  • Digital cartography creates maps using a
  • Making the map is often the final stage in a GIS
  • - 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.

Cartographic Elements
  • Border part of the map that extends beyond the
  • 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.

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

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Basic Map Elements
Map Features and Placement - USGS
Symbolizing Map Data
Types of Maps
  • Topographic
  • Thematic
  • Population
  • Land use
  • Temperature

USGS Topographic Map
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

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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.

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.

Classification of Choropleth Maps
  • Quantile Each class contains the same number of

Exploring classifications
  • You should visit the site
  • http//
  • 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

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.

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.

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.

Good maps
  • There are lots of sites that allow you to see
    good maps. A few are listed below
  • http//
  • http//
  • http//

A bad map
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

Simultaneous Contrast (left)
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Some Map Outputs
Some Map Outputs
Class Maps