Hydrographic surveying Australia equipment can be very expensive. However, they are also useful. From tide stations to sonars, each piece of equipment plays a special role in producing nautical charts to keep mariners safe.

Multibeam sonars

Just like any other type of sonar system, multibeam echo sounders transmit energy and analyse the echo or the return signal that has bounced off an object or the seafloor. The sonars emit sound waves from beneath the hull of the ship to produce coverage of the seafloor. Multibeam sonars produce soundings to ensure full coverage of the area being surveyed. The coverage area depends on the depth of water.

A lot of multibeam sonars can record acoustic backscatter data. This is intensity data that is processed to produce low-resolution images.

Professional survey units use multibeam sounder systems to get full and partial bathymetric coverage of the bottom throughout the survey area. This helps in determining the least depth over important items such as obstructions, wrecks, and dangers to navigation. Professional surveyors use different models of swath multibeam systems both pole mounted and hull mounted for survey operations. The echo sounder systems used must meet various specifications.

Side scan sonars

These are specialised sonar systems for detecting objects on the seafloor. Side scan sonars transmit sound energy and process the echo just like other types of sonars. Side scan sonars consist of three main components: a transmission cable, a tow fish and the topside processing unit. The transmitted energy in a side scan is formed into a fan shape that sweeps the floor of the sea from under the towfish.

A hydrographic surveyor uses the side scan sonars to record the echo and create a picture of the bottom of the sea.

Lidar

Lidar is the abbreviation for light detection and ranging and this special technology measures depth or elevation by analysing the reflection of laser light pulses off the object. These survey systems are aircraft mounted and provide continuous coverage between the sea and land.

Bathymetric lidar equipment is used to determine the depth of the water by measuring the delay time between the pulse transmission and its return signal. Laser pulses at two frequencies are often used: An infrared pulse of a lower frequency that is reflected off the surface of the ocean and a higher frequency that penetrates through the column of the water and reflects off the sea bottom. These two pulses are analysed to establish the depths of the water and the elevations of the shoreline. These systems can go up to 50 meters deep with good clarity.

Laser scanners

These are important pieces of equipment used in hydrographic surveying Australia. They use a similar technology as the bathymetric lidar. A lot of surveyors have installed various topographic lasers on their launches to locate features such as islets, rocks, and small islands. Sixteen laser beams are produced by the laser head. These beams reflect off the target object and are then received by the laser head as echoes. They are then analysed in a computer to determine the location and height of the object.