The section illustrated above was chosen as
there are two oceanographic phenomena - the near surface
internal wave packet and the mid water Kelvin Helmholtz wave
packet.
There are three EM302 configuration ("mode") changes involved
here:
- Shallow Mode - 1.1ms CW pulse less than 250m.
- Medium Mode - 2 ms CW pulse - 250 to 750m
- Deep Mode - 5 ms CW pulse - 750-1000m
The EM302 is switching back and forth from Shallow to
Medium on the floor of the NorthEast Channel and it is very
apparent that, for the purposes of water column imaging - the
Medium mode is to be preferred. This would contrast with the
bathymetric resolution requirement which would favour the
shorter pulse in the shallower water. As the vessel runs off the
shelf break, it switched to the longer pulse.