Fig. 5. Migration of inlet thalwag at New Pass, Florida (from Irish and Lillycrop, 1997).

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seismic technology is the frequency swept or Chip system. Chirp technology re-

duces the trade-off between signal range and image resolution. The Chirp system's

bandwidth, as well as frequency determines the spatial resolution. The Chirp swept

frequency sonar system emits a broadband FM source pulse having low frequencies

for depth penetration into the sub-bottom and higher frequencies for high vertical

resolution. The typical Chip data acquisition unit controls all data transmission,

recording and signal processing including analogue to digital conversion, compres-

sion of the FM pulse and spherical divergence correction. The recorded signal is the

output of the correlation filter used for pulse compression and is usually stored in

industry standard SEG-Y format.

A series of hydrophones trailed behind the boat receives the return signal. Simi-

lar to GPR, energy that penetrates the sediment is reflected off changes in lithology