Traditional echo-sounders use a technology tested and apt to be used at depth greater than 1 m, but require the immersion of the sensor at least 60/70 cms.

The use of an acoustic echo-sounder in shallow-waters enviroments with rocks, emerging obstacles, or rapidly rising bottom asks for a constant attention during the survey, and a limited operative speed, to avoid transducers damages.

Water turbulence around the transducer could produce unreliable measures during high-speed surveys, or strong stream, or for the gas presence (also organic) in sediments.

For several years SOA has carried out shallow-water surveys using prism and total station as well as traditional echo-sounders, taking advantage from high speed transfers between subsequent measuring stations, while performing the soundings using the hovercraft in floating setting to gather proper transducer immersion.

This necessity and a strong consumption of the bottom hull strongly reduced remarkable hovercraft advantages in river surveys.

A recent improvement in our survey techniques and instrumentation led us to overcome these problems.

Using new Electromagnetic Sensors, with no submerged transducer we are now able to carry out our survey employing our hovercrafts in "air-cushion" setting at high speed 30/35 knots) avoiding obstacles and operating in super-shallow areas.

This new technique open interesting perspectives in the field of fluvial and lacustrine bathymetries, giving solution to two main problems affacting these environments, accessibility and presence of obstacles.

The operative speed of the system and the mts. cost permit the continuous scan of remarkable extensions, allowing therefore the matching with land digital models obtained through LIDAR relief.

Operative characteristics
- fresh waters
- relief max depth 8 mts.

The advantages in short
- productivity
- accessibility
- same relief of submerged or emerged zones
- low environmental impact
- costs