ArcGIS Resource Center

In a previous post we described the newly added application template gallery, a feature of the ArcGIS.com viewer that’s available when you share your map. A very nice new template (authored by John Grayson of Esri’s Applications Prototype Lab) was just added that enables you to compare three ArcGIS Online maps side-by-side. This comparison template has been featured at several recent conferences and at other events, and now it’s available for anyone to implement. Let’s take a closer look.

Using the ArcGIS.com viewer, you’ll find the template when you open your map or other maps shared via ArcGIS Online. Click share:

And choose Make a Web Application:

You’ll find the comparison template along with many others you can choose from:

You can choose Preview for a quick look, but download the template to implement it from your own website. After unzipping the download, take a look at the readme.html file to learn how the template is organized and how you can customize it with your own maps. It’s very simple – just edit the layout.js file (shown below) and insert IDs for three maps of your choosing.

The map ID is unique, and is found in the URL when you open any map. For example, the URL below is the link to one of the maps currently featured at the ArcGIS.com Gallery:

http://www.arcgis.com/home/webmap/viewer.html?webmap=12dccf99d82749aeb864259ee0854c7b

The unique ID appears after webmap= . Just insert the map IDs in the layout.js file as shown below:

They can be maps that you’ve created, or any other publicly shared ArcGIS Online map. Here’s an example that compares maps showing USA diabetes, obesity, and poverty rates:

One of the features of this template is that you can synchronize all three maps together, so they zoom and pan to the same location and scale. Just check the boxes shown below:

You can also choose the map information that you would like to display for all three maps:

And use the Identify tool to display information about features at the same location in each:

Here’s another example comparing current and recent fires from GeoMAC, social vulnerability, and daytime population:

You can also modify the source JavaScript to tweak the look and feel of the template, add your own tools, and more. The possibilities are as endless as there are ArcGIS Online maps!