Exploring the Information

In this, the final section of the tutorial, you will learn how to explore the map information by working with layers and examining the attributes of various map features.

Layer List

To understand this better you may wish to take a look at GIS Concepts page where we discuss layers.

Because there are often many layers available for a map, map layers are organized into related folders on the Layer List (if you don't see the Layer List, click on the tab in the Information Panel). When you initially open the map, some folders may be open and some may be closed. Likewise, some layers may be turned on while others may be turned off by default.

Turning Layers On and Off

To manually set the display of layers, you can open a closed folder by clicking on it. A list of all the layers contained within the folder will be shown. Similarly, you can click on an open folder to close it. Notice that opening and closing folders doesn't turn layers on or off; it simply helps you stay organized.

Next to each folder you will see a checkbox which indicates whether or not a layer is visible on the map. A layer is 'on' (displayed on the map) when there is a check in the checkbox. Toggle individual layers on and off by clicking an empty box to make the layer visible, or clicking a checked box to hide the layer.

Figure 2. The Layer List

Making Layers Active

Some layers are only available at certain scales. Layers that are available at your current scale will be shown with a white identify icon ( Figure 3) next to the layer name, while layers that are unavailable at a given scale are shown with a grey identify icon (Figure 3) next to the layer name. A layer can be made 'active' by clicking on the white icon adjacent to its name. A black identify icon (Figure 3) will denote the active layer, and its name will be highlighted in blue in the Layer List. When a layer is active, you can work on and interact with that layer in the Map Window. You can have numerous layers active at any one time.

Figure 3. Available Layer (white), Active Layer (black) and Unavailable at given scale icons (grey)

So, what the heck does all this mean? When a layer is active, it means that a spotlight is on the layer. In other words, this is our way of telling the computer that this is the layer in which we are interested. How is this relevant, you ask?

Wow, you ask a lot of questions. Read on.

Identifying Attributes of Features

As discussed in the Introduction to GIS, features have attributes associated with them in Geographic Information Systems. Suppose you are interested in the attributes associated with a street in a particular location to which you have zoomed. First, ensure that the layer with street attributes is the active layer (see Making Layers Active for more information). In this case, ‘Streets (10000-20000)’ is the layer made active.

Next, use the Identify tool to get attribute information about the street by clicking on it. Select the Identify tool whenever you want to examine the attributes of a feature on the map.

Attribute information can be displayed in a few different ways. Once you select one of the options listed under ‘Reports,’ the attribute information is displayed in a separate Selection Reports window.

For more information on identifying features, see the Tools & Tasks page.

Map Legend

In addition to the functions above, the Layer List can also display a Map Legend. To make the legend visible, click on the ‘View Legend’ button at the bottom of the Layer List. To hide the legend, click the ‘Hide Legend’ button. Legend symbols will only be visible for layers that are turned on.

Figure 4. Activated Layer List Legend

Congratulations! You've finished the basic tutorial. Pretty painless, wasn't it?

While we've only scratched the surface of what can be done with web-based GIS during this basic tutorial, it is our hope that we've perhaps opened your eyes to the power of this technology.

Now, we encourage you to start working with the mapping system to put to use the information we've shared. While we've shown you the basics, we hope you’ll spend some time reading the Tools and Tasks section, to learn how to use the tools and functions of the mapping system.

We’ll tell you how you can draw on and add your own things to a map, create your own custom maps as PDF documents (which you can save and/or print), measure distances, select features based on various criteria, search for features, and a whole lot more. We don't claim all these tasks are dead simple, but we work hard to make everything as easy as possible.

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