As an organizer of event you prepare data for activity with QR codes as checkpoints. It may be orienteering event, quiz or similar activity. Users record their presence and decisions at checkpoints or answer questions using QREvented app as client. GPS coordinates also may be used as virtual checkpoints. QREvents and QREvented itself exchange information by QR codes. QREvents gives some preliminary results of event. Now you can use public QR code on orienteering polygons. Controls with BLE beacons and NFC tags also may be used.