Some layers in your web map may be continually updating, for example a GeoRSS feed or a feature service being updated by workers performing edits while in the field. When the map or layers are redrawn, these data refresh. But by using the refresh interval on these layers (introduced in the September 2013 udpate), you can force an automatic refresh at a specific time interval. These refreshes occur even while the map is open and idle, and will synchronize the map anywhere it is accessed – via browsers, desktops, and devices*.
Example: USGS Earthquakes
Continually updated earthquake data is published by the USGS in a variety of formats, the one we’ll use is the Atom syndication. In the upper right of the page is a list of available feeds showing earthquakes of various magnitudes ranging in time periods that range from the past hour to the past 30 days.
Below we’ve right-clicked All earthquakes in the past hour to show the choice to Copy link address. Your choices will vary depending on your browser, but copy the link for the desired feed. Note that the update interval for the past hour feeds is every 5 minutes:
Add the feed to your web map
Open a new web map and choose Add, then Add Layer from Web:
From the drop down list choose GeoRSS and paste the link you copied from the USGS website into the URL:
Our map now displays earthquakes that have occurred over the last hour. Since we know the feed is updated every 5 minutes, we can set the refresh interval on the layer to match.
Click the arrow next to the layer name, then choose Refresh Interval. Make sure the refresh box is checked, and enter your desired interval (in this case 5 minutes). The interval must be expressed in minutes, but can be in the range 0.1 (6 seconds) to 1440 (1 day).
When you save the map the layer properties persist, and the layer will automatically refresh at your specified interval.
For more information see:
*Depending on layer type, for example as of this post GeoRSS layers are not supported via ArcGIS Online web maps in ArcGIS for Desktop and the ArcGIS application for iOS and Android.