Fig. 4
From: An autonomous GPS geofence alert system to curtail avian fatalities at wind farms
Timing and locations of GPS fixes and SMS alerts received during geofence field trials. Flight path of the helicopter used to field-test the performance of the geofence transmitters indicated by the black line with directional arrows. GPS location fixes from the two transmitters (purple and green points) are labeled with the time each fix was acquired. Banner labels show the times and locations that SMS alert messages were received after the transmitters crossed the 20 km geofence alert zone (red shaded region)