About displaying layers
ArcGIS includes many layer display options that are used to portray geographic information. There are numerous ways to represent layers using symbols, colors, and labels. The topics in this help section cover how to symbolize and render layers.
Layers form the primary building blocks in GIS maps. Within each layer, symbols, colors, and text are used to portray important information that describes each of the individual geographic elements.
Features have geometry that defines their location and shape (for example, points, lines, and polygons) as well as attribute values. A wide range of renderers are used to assign map symbols based on attribute values.
Features are also often labeled using their attributes as well. See the help section on Adding text to a map for information about the use of labeling and annotation.
Symbols and renderers
ArcMap includes a number of alternative methods for portraying geographic datasets by applying symbols and graphics. For features, symbols are assigned to each feature based on attribute values, and particular methods are used to render each layer. For example, water bodies and streams might be shown with a single, constant blue color. Roads might be symbolized based on road class. Seismic events, such as earthquakes, might be represented using graduated symbols based on their magnitude. And polygons might be classified based on land use.
ArcMap includes a number of renderers to create these layer displays. Renderers are methods for displaying geographic information through the use of symbols and display techniques. In this part of the help, you'll learn about various alternative renderers that you can apply to your datasets when you create layers to portray them.
You will begin to learn about various renderers in the next help topic, A quick tour of displaying layers.
One of the alternatives that you can use to portray features using map layers is to use cartographic representations. A cartographic representation is a set of symbols, rules, overrides, and graphic edits that allow you to represent features cartographically without having to modify the underlying feature geometry. See Advanced layer display using representations for more information.
Using attribute fields
Two key aspects of layer display are the assignment of map symbols based on key feature attributes and the use of attribute fields for map labels. As you read through the help topics in this section, you'll begin to see and understand the critical role that feature attributes play in the layer rendering and display options that are available in ArcMap.
Using data classes in layers
Often, symbols are assigned to features based on a classification, such as a road class. In other cases, numeric data can be classified to portray quantitative information, for example, to show population density or the age breakdown of a population in each county or to show the value of certain parcels within a community.
When classifying numeric data about features, you can use one of many standard classification methods provided in ArcMap or you can manually define your own custom class ranges. You can learn more about data classification options in Classifying numerical fields for graduated symbols.
Improving your layer display using advanced options
A number of advanced techniques are used in ArcMap to create more effective layer displays and maps. You can learn about these techniques in this part of the help as well. These include
- Using color transparency within map layers.
- Controlling the drawing order of features in your map using Symbol Level Drawing. With this technique, you specify the display order of features using symbols.
- Using the Effects toolbar to interact with your map display and to flash features.
- Creating useful and effective symbol legends that appear in your table of contents and in page layouts.