Legends help your audience recognize and understand data that is displayed on a map. The March update of ArcGIS Online introduced Interactive Legend, a new map-based configurable app that allows you to explore feature layers in the map by interacting with the legend.
This article will illustrate how to choose the best configuration options to craft an engaging experience for your audience, and introduces some new tools including the ability to take screenshots. The steps for creating an app from a map are described in this help article.
To use this app, you will need a web map with a feature layer using one of the supported drawing styles, see Supported Drawing Styles below for the details.
You can use the interactive legend to emphasize a specific category or set of categories to gain a deeper understanding of the data and how its distributed over space through a simple user interface.
For example, the Global Power Generation referenced below shows the distribution of different types of power generation used around the world. The Interactive Legend app allows you to explore this data to ask and answer questions in an interactive way. Using the legend, you can click on the Hydro primary fuel category. This allows you to understand the distribution of Hydro power generation and click on individual map features to find out more about a specific plant.
Feature filter is the visualization mode used in the Power Generation app. When you select an interactive category or categories in the legend, all features that are not a member of the categories are removed from the view. This enables you to really focus on specific categories as you explore the different categories of the dataset without being distracted by all the available categories. For example, if you want to focus on understanding the distribution of just renewable energy generation across the world, you can select the Hydro, Solar and Wind options in the legend.
The Mute visualization mode creates an interaction, in which all the unselected features in an application are de-emphasized (muted), effectively moving them into the background of the visualization. This brings the focus to the selected categories, but also allows your audience to still see the full distribution of the data.
In the example below, the app displays where spacecrafts have landed when they return to earth. The landing sites are categorized by project. When Apollo is selected in the interactive legend, all the other landing sites are displayed as gray, moving the visual focus to the Apollo landing sites. (Gray Scale 100% Opaque: 30%)
Mute mode can be configured to use gray scale and opacity to determine the visual effect on de-emphasized features. App authors can determine the amount of gray applied to these features. A value of 1 displays the symbology as shown in the original map and 100 displays the muted values as completely gray . Opacity can also be used in combination with gray scale or separately to help unselected values blend into the background. The key is to create a visualization with a large contrast between the muted/non-muted features. The example below uses 25% opacity and 30% gray scale to emphasize the Apollo landing sites, while still preserving some of original color.
The primary purpose of the Interactive Legend app is to enable your audience to explore the map by emphasizing different classifications data. But you might want to include other things to support the message of your map. For example, both of the apps above included a splash screen to help introduce the topic of the map. Interactive Legend includes these additional options:
- Splash screen
- Layer List
- Search – feature search will honor what is currently filtered by the legend.
- Basemap Toggle
- Screenshot tool
- Help panel
- Feature Count
- Zoom to button
The Screenshot tool will let you capture an image of the map, with the option to include a legend or the pop-up for a feature. This allows you to create a static version of the map further sharing or inclusion in a report. The Help panel provides in app documentation to support the use of the Interactive Legend and Screenshot tools.
The last two are new features, as of June 2019, which allow you to show the number of features in the current extent and zoom to the extent of features that are currently visible based on the element(s) selected in the legend.
Supported Drawing Styles
The drawing styles currently supported by the interactive legend app include:
- Types (Unique symbols)
- Predominant Category
- Counts and Amounts (Size) – Classify Data Checked
- Counts and Amounts (Color) – Classify Data Checked
- Predominant Category and Size (Partially interactive)
- Types and Size (Partially interactive)
- Relationship and Size (Partially interactive)
- Location (Single symbol)
When working with the two Counts and Amounts drawing styles, you will need to ensure that the data has been classified in order for it to be supported by the Interactive Legend. The last three listed are newly supported as of the June 2019 release.
When working with the three partially interactive drawing styles, keep in mind that the size portion of the legend will not be interactive, but you will be able to filter the data based on the category or type elements of the legend.
If an unsupported drawing style is used in the app, a message will be reported in the configuration panel noting that the map contains a drawing style that is not supported for interactivity.
The two examples included maps using the Types (Unique symbols) and Types and Size drawing styles. You can explore other examples in this gallery.
We look forward to see the apps that you will create with this new configurable app. Please share your great work and join the conversation on Geonet.