HAWAII MR1 Swath Capabilty

The HAWAII MR1 is an acoustic swath mapping system that simultaneously acquires digital bathymetry (swath width > 3.4 times water depth) and sidescan sonar imagery (swath width > 7.5 times water depth). The HAWAII MR1 swath width is unlimited in the sense that data are acquired throughout the duration of the transmit/receive cycle. However, the effective swath width is defined by a critical signal-to-noise ratio that occurs as the strength of the received signal decreases through the length of the transmit/receive cycle.

The following graphs and explanations describe the practical swath widths of HAWAII MR1 bathymetry and acoustic imagery.

Bathymetry Swath Width

The HAWAII MR1 bathymetry swath width is presently defined by the first acoustic multiple, which results in a total angular width of 120°. This corresponds to a swath width equal to 3.4 times the water depth (that is, in 2000 m water the full bathymetry swath is 6.8 km wide). In some cases the swath width can extend beyond the first multiple, for instance in shallow water or over reflective seafloor. Bathymetric precision is limited by the signal-to-noise ratio, which varies as a function of slant range, bottom reflectivity and grazing angle. A quantitative study of MR1's sister system, SEAMAP, and Sea Beam bathymetry collected simultaneously over the Jan Mayen Ridge in the Norwegian Sea showed that SEAMAP depth soundings were within 1.0% of the Sea Beam soundings [Lingsch and Robinson, 1994]. Similar good agreement has been found in comparison to Hydrosweep and Simrad EM-12 multibeam bathymetry.

Select one of the following to see a graph of bathymetry swath width versus water depth:

Sidescan Swath Width

The width of the HAWAII MR1 sidescan sonar swath is a function of the towfish altitude over the seafloor and the period of the transmit/receive cycle. Using a typical towfish depth of 100 m, a transmit interval of 12 seconds in 2000 m total water depth results in a HAWAII MR1 sidescan swath width of approximately 17 km.

At far range the system is limited by signal:noise. However, previous deep water surveys (6000 m) have shown that sonar targets are readily identifiable in swaths greater than 27 km wide in the sidescan data.

Select one of the following to view a graph of sidescan swath width versus transmit interval: