Brazilian rivers are a particularly challenging navigation environment because of frequent changes in bathymetry due to sediment transport. To accelerate the release of hydrographic information for these regions, the Brazilian Hydrographic Office has been investigating efficient ways of riverine surveying. In this context, Phase Measuring Bathymetric Sonars (PMBS) are being considered because of their potential to provide wider swaths than traditional Multibeam Echo Sounders (MBES) in shallow waters. Although these systems used to have severe limitations in sounding quality and nadir density, new models with multiple stave pairs are being built to overcome these issues, including the EdgeTech 6205, which claimed to use beamforming to resolve nadir gaps, a long-term problem of PMBS.

This research reproduced conventional phase detection algorithms and compared them to an in-house developed differential phase Direction of Arrival (DOA) estimator, which used phase-delay beamforming to constrain the receiver elevation angle sensitivity. To assess the performance, a shallow water region, known to have meaningful characteristics, such as rough, smooth, target-filled, and seafloor gradient, was investigated by both an EdgeTech 6205 and, as a benchmark reference, an MBES Kongsberg EM2040P, already well-assessed and used in high-quality hydrographic surveys around the world. Depths were comparable to shallow rivers to assess if it would provide reasonable quality and efficiency for riverine surveys.

The results obtained indicated that the use of beamforming significantly contributed to multipath and noise suppression. At the same time, the system evaluation attested to its potential to be used in hydrographic surveys, being an efficient alternative to conventional multibeam systems for IHO S-44 Order 1 riverine surveys.