Agents of Discovery players will find your GPS-based Challenges by using their in-game scanner. This will unlock Challenges within a set proximity to the player. You can customize the scan radius by going to the My Missions page and clicking “Edit Map” for the chosen Mission.
If you have a small Mission, you may want to make your scan radius smaller so players have to explore your entire Mission area to unlock all the Challenges. If you have a larger Mission, you may want to make the scan radius larger so it is easier for players! Scan radius only applies to GPS Missions or Mixed Missions.