The Secret to Effective Geofencing

You’ve probably heard of geofencing, but in case you haven’t, geofenced notifications are alerts that users receive on their smartphone when they are near a particular location. They are a powerful activation & re-engagement tool for location based apps because they communicate information to a user at a time that is contextually relevant. Over the past year, geofenced notifications have become popular with many shopping apps such as RetailMeNot, RedLaser, etc. In this post I’ll cover some of the basic problems you might encounter with developing geofencing.

1. Inaccurate Location Data
The dirty little secret of most location data providers is that their data just isn’t that accurate. Typically for geofencing you will want to geofence a small radius (ex: 150 meters) around the point of interest. The way these data providers get latitude & longitude information is through a method called address interpolation. The problem is that the latitudes and longitudes from this method can often be off by hundreds of meters. This means when a user is standing directly at the point of interest, there is a good chance they will not fall into the geofencing radius! To overcome this problem you either have to manually fix the location data (like eBay did) or use user data to automatically correct the locations.

2. Battery Drain on Android
Android has built in support for geofencing, but unfortunately it has severe battery drain issues on certain versions & devices. To work around this issue, many developers have taken to developing their own proprietary geofencing framework based on polling GPS. However, a lot of attention needs to be given into tweaking the framework to ensure users receive notifications in a timely manner, but without significantly draining their battery. Some ways to decrease battery drain are to poll less frequently, or instruct the device to only use wifi data to get a location fix rather than turning on the GPS.

3. iOS’s hard limit on the number of geofenced regions
Thankfully, iOS has a geofencing framework that doesn’t seem to drain user’s batteries. Unfortunately, iOS sets a pretty low limit on the number of regions you can monitor. This means to geofence effectively, you need to update which regions your geofence as a user moves around. Luckily, iOS has another framework that will wake up your app when the user has moved a significant distance (on the order of 5-10 miles). You can use this framework to wake up and update the regions your app is geofencing.

These are just a few of the problems that might be encountered when developing geofencing, but geofencing is such a powerful engagement tool and it is well worth the effort.

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