Most of what Arcview consists of is themes. The theme is the one of the
most important components of GIS. A view consists of one or more themes
layered on top of each other. In this section, the following parts of a
theme will be covered:
The concepts covered in this exercise will be:
- Adding a theme
- Creating a new project
- Changing the symbols of a theme
- Classifying and customizing a classification method
Suppose you wanted to use another theme not present in the View. The theme
has to be added.
- Click on the button titled Add Theme, it is the second button
in the top row.
- Double click on the esri folder, double click again on the folder
called esridata. Scroll down the list until you see the folder labeled
world and double click on that. On the left screen is a list of
files. Double click on the file called country.shp.
- Activate(refer to the introduction, if you have forgotten) it and turn
it on. A world map should appear on the right side of the screen.
- Deleting a theme does not remove the theme from disk. It only
deletes the theme from the current project. To delete a theme, activate
the theme to be deleted(country.shp), go to the Edit menu and select
Delete Theme. Answer "yes" in the delete themes dialog box.
The Legend and Symbol editor change the way data looks either through
changes in the feature classification or through changes in the legend
- Activate a theme and double click the legend. The Legend
Editor should open with information on the way the data is grouped and
classified. More information is in the exercise that follows.
Close the Legend Editor.
Classification of a Theme
Classification of data involves grouping data so that the data is more
understandable. There are different ways of classifying data,
only a few of which will be explained here:
- Graduated Color
Unique Value Dots Charts
These are different classification methods, i.e, different ways of
- Graduated color is a way of showing data by using a color ramp for
showing different classes of data. For example, if there is a population
range, then the lightest color will be for the smallest population and the
darkest color will be for the largest population. This method is used to
change the legend type and thus influence the way data
- Quantile method creates classes that have the same number of features
in each class.
- If unsatified with any of the classifications, you can make your own
classification. Making a custom classification is covered in the
In this exercise,various concepts of classification are covered.
- Go to the File menu and select Close All. This closes all open windows
in the project. Go to the File menu and select New Project. When the
dialog box pops up asking whether to save changes. Click No.
- Highlight the View icon and click New. Maximize the ArcView GIS and view1 windows.
- Click on the button titled Add
Theme. When the dialog box opens up, double click on the c:\ folder
and then double click on the basins folder. This folder contains all the
data for the Cahaba River.
- Double click on the folder named "data" and then on the folder
- On the left there will be a listing of all shapefiles which can be
themes. Hold down the Shift key and select
dam.shp, rf1.shp, cat.shp and cnty.shp. You will need to
scroll down the list to find all the themes. Release the shift key. Click OK. Turn all themes on.
- Go to the View Menu and select Properties. Highlight View1 in the
Name field and type in any name(for ex: Cahaba) for your View. Click
Ok.Notice the name change in the View window.
- In the Table of Contents, make sure the order of the themes are as
follows:rf1.shp, dam.shp, cat.shp, cnty.shp from top to bottom. This is to
ensure visibility of all themes. If this is not so, click and drag the
theme(s) so that they are in the proper order.
The dams are hard to see because the circles representing them are
too big. Open the symbol editor for the dam.shp theme by double clicking
on the theme's name in the table of contents. Notice the symbol in the
is a dot. Double click on the dot in the symbol box. This opens the
symbol editor. Click the drop down arrow in the size window, scroll up
and click on 4. A 4 should appear in the size box. Exit the symbol window
by clicking on the X in the upper right hand corner. Click apply in the
legend editor. Exit out of the
Double click on the cnty.shp theme to open the Legend
Editor. Currently the legend type is Single Symbol. Click on the
"Legend Type" drop down box and select Graduated Color. The Editor's
appearance changes. Click on the drop down box in the "classification
field" and select Area.
- Using the Legend and Symbol Editors: rf1.shp is the theme
representing the Cahaba river. If the theme is not blue, double click on
the legend to open the Legend Editor. Double click the line in the
Symbol box to open the Symbol Editor. Click on the button
with the brush. Change the color to blue. Exit out of the color palette by
clicking the "X" on the upper right hand of the box. Click Apply in the
Legend Editor. Exit out of the Legend Editor window. Likewise change the
colors of any other themes that are not readily visible.
The classification field is the attribute shown on
the theme. Therefore, in this theme different classes of area will be
the Alabama county map.
Click on the classify button. Change the type to Quantile by
clicking on the "Type" drop down box and selecting Quantile. Click
on the Number of classes drop down box and select 3. Click Ok.
Under the Normalize field, you see a row of boxes under the
headings: symbol, value and label.Highlight the first box under the
heading Label. Highlight the value and type Low. Highlight
the next Label box and type Medium and in the next, type High. Click
apply. The Quantile classification is customized for your
presentation where the distribution of area among the counties is
divided into low, medium and high. Close the Legend Editor.
On the right side of the Table of Contents, the county map has been
classified using Graduated Color with the county
area as the classifying field and classifying method is Quantile.
Summary:In this exercise, you learned to open a new project, change
and colors of a theme and change the legend type and classification method
of a theme. You also learned to customize a given classification method.
Unit Summary: :In this unit, you learned how to
add a theme,
delete a theme, customize a
open a new project and also had a brief introduction to the symbol editor.
If you want to go to the next unit, keep Arcview running and do not delete
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