There are four types of triggers that are used in AR. The decision of which type of trigger to use can be based on the location of the AR activity you want to use and the opportunity to place a trigger at the site.
Location (latitude, longitude)
We can use latitude and longitude to trigger an AR event. Most devices (smartphones and tablets) now have a built-in GPS that will continually monitor the location of the device. We can use that and set up a zone around a GPS location (latitude and longitude) and when the device moves into the zone, it will trigger the event. You will need to know the location of the trigger point and the active distance (a circle) around it in which it is active. You can use Google Maps or another mapping program on your device to find the latitude/longitude of a place.
A QR code is a high contrast code that is generated for a specific webpage address (URL). There are online generators for QR codes, and they can be used printed out, or even on another device. See this powerup on how to create a QR code. The AR game uses the devices camera scanner to read the QR code the send you to the specific URL.
An image works just like a QR code to trigger an event. However, an image needs to have some high contrast. A symbol works great, and even a photo of a sign with a good contrast between the words. Images of forests, parks, etc do not work well. The AR game can use the image to go to a specific webpage (URL) or even trigger another AR event, like playing video or audio file.
A beacon is a small Bluetooth device that triggers an AR event when your smartphone/tablet moves close to it. You can set the distance from the beacon a person needs to be to trigger the AR event. Beacons are great for setting up an AR game inside a building when you don’t have GPS coverage. They can be hidden so people can’t see them, unlike a QR code or image that needs to be displayed and scanned to activate the trigger. The downsides are that beacons cost money, have a battery that will eventually run down.