Map Basics: Working with Layers


The Layer List

The Layer List, located to the left of the main map window, contains the names, status, and symbology of the layers offered in the Interactive Mapping Service.

Since a large number of layers are available, the Layer List is organized into folders:
Below the folder level, some individual layers are grouped with other related layers into group layers:

The Layer List (default view)

The Default Layer List

Showing and Hiding Layers

By default, folders (Cadastral, Topographic, Aerial Photos, etc.) are closed when you first open the Interactive Mapping Service.   You can open a closed folder by clicking on its closed folder icon (  ).   A list of all the layers and group layers contained within the folder will be shown. To close a folder, click on its open folder icon (  ).   Notice that opening and closing folders doesn't turn a layer's visibility in the map on or off; it simply helps keep the layer list uncluttered.

Similarly, a closed group layer can be opened by clicking on its closed group layer icon (  ). A list of all the individual layers contained within the group layer will be shown. To close a group layer, click on its open group layer icon (  ). As with folders, opening and closing group layers doesn't turn a layer's visibility in the map on or off; it only contributes to an uncluttered layer list.

Next to each folder, layer, or group layer is a checkbox that indicates whether layers are visible in the map.  A layer is 'on' (its features are visible in the map) when there is a check in its checkbox, its folder's checkbox, and its group layer's checkbox.  In the Interactive Mapping Service, some layers are checked by default, while some are not.  Also, keep in mind that some layers are set to be visible only at certain ranges of map scale.

While checkboxes are provided at both the folder and group layer levels to allow users to turn all sublayers on or off with one click, folders and group layers work differently.   When you select or deselect a folder's checkbox, the checkboxes of all layers inside the folder automatically are selected or deselected.   Selecting or deselecting a group layer's checkbox will not change the checkboxes of the individual layers in the group layer.  When you select a group layer's checkbox, every individual layer whose checkbox is already selected becomes visible in the map, as long as the layer is set for visibility at the current scale.

Folders and Groups in the Layer List

Managing Layers with the Layer Explorer

The Layer List may be customized to include only layers of interest by removing layers that are not needed or used.

To open the Layer Explorer, click "Manage Layers," located in the lower left corner of the Layer List. Layers with a green checkmark will appear in the Layer List; features from those layers will continue to be available for selection and display in the map. Uncheck the layers you wish to exclude from the Layer List. When every layer within a group is excluded, the group layer will be removed from the Layer List.

Layer Explorer

Layer Actions

Layer Actions, or functions and tasks related to the properties of individual layers, are provided where individual layer names are underlined in the Layer List.  To perform an action on a layer, left click the underlined name of a layer in the Layer List and select an action from the menu that appears a moment later.  Keep in mind that not all of the following layer actions will be available for every layer.

A Sample Layer Actions Menu

Swipe Layer
The Swipe Layer action allows users to swipe (or roll out of view) a layer to reveal the map features that lie underneath the layer.  Click the layer you want to swipe and select Swipe Layer. The map will redraw with a swipe window overlaying the main map window.  To swipe the layer, drag one of the overlay window's borders. You can swipe vertically or horizontally.  To close the overlay window, click   Close Swipe Overlay   in the swipe window's upper right corner.

Swiping a layer from left to right

Show/Hide Labels
The features of some map layers are labeled in the map.   An example of feature labels are house numbers associated with tax parcel polygons.   When labels are not desired in the map view, such as when details are obscured in the map, left click on the layer of interest to access available layer actions and choose "Show" or "Hide" to turn labels on or off.
Zoom to Visible Scale
The Zoom to Visible Scale action allows you to zoom directly to a scale at which the layer is set for visibility.   Use this action when you want to view features in a layer that is not visible at the current scale.
Zoom to Full Extent
The Zoom to Full Extent layer action zooms directly to the extent of all features in a layer.   Note that this extent may be different from that provided by the Zoom to Full Extent tool in the Navigation toolbar.   Also, if the scale at a layer's full extent is beyond the visible scale of features in that layer, the features will not be visible.
Symbolize Layer
The Symbolize Layer action allows you to customize the appearance of features in layers that are added to the map via the Upload Shapefile tool in the Project toolbar.
View Layer Metadata
Metadata, or “data about data,” is background information about a layer such as its source or creation date.  This action displays a layer's metadata in a new browser window in either a “frequently asked questions” (FAQ) format or in the Federal Geospatial Data Committee (FGDC) standardized format.

Making Layers Active

Some layers are available only at certain scales. Only features from layers that are visible at the current map scale and set as "active" can be queried and selected in the main map window.   By default, the "Tax Parcels" layer is set as active in the Interactive Mapping Service.

Layers that may be made active at your current scale will be shown with a white "available" icon ( Available Layer ) to the right of the layer name, while layers that are unavailable at a given scale are shown with a greyed-out "unavailable" icon ( Unavailable Layer ) to the right of the layer name.  When a layer is unavailable, zoom in or out until its name in the Layer List is no longer greyed-out.  A layer can be made active by clicking on the white icon adjacent to its name.  A black "active" icon ( Active Layer ) indicates that a layer is active, and its name will be highlighted in blue in the Layer List when it is within its visible scale range, or in grey when it is beyond its visible scale range.  Multiple layers may be active at the same time. To inactivate a layer, click its black "active" icon.

When no layers are set as active, and querying or selection tools are used in the map, the following message appears in the bottom half of the information panel:

Select the layer you wish to set as active from the drop-down list.

Viewing the Map Legend

In addition to the functions above, the Layer List can also display a Map Legend, or how a layer's features appear in the map (symbology).   To make the legend visible, click the "View Legend" button at the bottom of the Layer List.   Group layers must be opened to view the symbology of individual layers within group layers.   To hide the legend, click the "Hide Legend" button. Keep in mind that legend symbols are shown only for layers with features visible in the map.

Layer List Legend

The following sections will show you how you can draw on and add your own data to a map, create, save, and print your own custom maps, measure distances, search for and select features based on various criteria, export data, and more:

> More Advanced Functions