Step 1: Differences between frequency and time domains
Step 2: Advantages of helicopters over fixed-wings
Greatest advantage of AEM is transmitter and receiver(s) are both onboard the fixed-wing or helicopter aircraft. That makes it a relevant tool to cover wide areas efficiently. Helicopters acquiring in the time domain is however now the most common AEM technique since it could fly slowly and at very low altitudes (i.e. 30 meters), increasing considerably the magnetic dipole strength. Additionally, helicopters low velocity flights enable to follow sharp topography more easily.
