GIS Data Visualization and Presentation

Intro GIS

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 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.

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.

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.

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.

TITLE

INSET

MAPFIGURE

LEGEND REFERENCES

GRATICULE

SCALE

BORDERNEATLINE

INSET

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

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

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 features.

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

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://www.lib.utexas.edu/maps/index.html• http://www.esri.com/mapmuseum/index.html• http://nationalatlas.gov/printable.html

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)

Some Map Outputs

Some Map Outputs

Class Maps#

#

#

#

#

#

#

#

#

##

#

#

#

#

#

##

#

#

#

#

#

#

#

#

#

#

#

#

##

#

###

#

#

#

#

#

#

#

# #

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

##

##

#

#

#

##

#

#

#

##

#

#

##

#

#

#

##

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

##

#

#

##

#

#

#

#

# #

#

# #

#

#

#

#

#

##

#

#

#

#

#

#

#

#

#

#

#

#

##

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

##

#

##

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

#

##

1 0 1 Kilometers

N

380000

380000

381000

381000

382000

382000

383000

383000

384000

384000

385000

385000

386000

386000

387000

387000

4696000 4696000

4697000 4697000

4698000 4698000

4699000 4699000

4700000 4700000

4701000 4701000

4702000 4702000

hirolandcpAgricultureDevelopedExtractiveForestWetland

Points201.shp# Agriculture# Developed# Extractive# Forest# Wetland

Clip1cs.shpClip1rd.shp

Land Cover of the Ithaca East ParcelHand Digitizing

Created by Hiroaki Nakayaon April 30, 2001. Land cover interpreted from NAPP aerial photo 8052-119 and1: 24,000 USGS Ithaca East topographic map

1:36872

Ellis Hollow

Ellis Hollow Creek

Baker Hi ll

Turkey Hill

Quarry