Sonar data provides an excellent means of interpreting underwater structures and is often the only viable option in challenging environments where traditional sensors, such as cameras or laser scanners, fall short due to physical or environmental limitations.
Sonar is commonly used in surveying by mounting it to the hull of a boat, just below the waterline, to scan the seafloor. When combined with GPS positioning data, the sonar output can be processed in real time and automatically mosaicked using survey acquisition software. For greater detail, sonar can also be mounted on remotely operated vehicles (ROVs) or autonomous underwater vehicles (AUVs), allowing closer mapping of specific areas than what is typically achievable from the surface.
However, this approach introduces a challenge: accurately positioning the ROV. With advanced software, data can be processed using semi-automatic mosaicking methods. Raw sonar captures are extracted as individual images and precisely aligned within GIS software. Algorithms for stitching and blending these images are used to create a seamless, homogenous mosaic. This mosaic can then be georeferenced onto existing plans and orthophotos, enabling detailed identification and mapping of features for further analysis.
Over time, multiple mosaics can be layered to monitor changes in the environment. Additionally, vectorizing the data to map specific points of interest enhances compatibility across different software platforms and fosters collaboration with related fields. This process ensures that sonar data is not only accurate but also versatile for a wide range of professional applications.
TWO-Dimensional semiautomatic mosaicking without GPS positioning data
AUS-ROV engineers have developed a semiautomatic sonar image mosaicking method which does not require navigational positioning. The raw sonar data is extracted as single images and precision aligned in GIS software. Algorithm for stitching and blending is used for processing all images in one homogenous mosaic. As that it is georeferenced on existing plans or orthophoto. With sonar mosaicked data all details can be identified and mapped for further analysis. Multiple mosaics can be stacked and changes can be monitored over time. Vectorising data, mapping details of interest, further improves interoperability among the different software platforms and connects to other branches of similar profession.
Three-dimensional multibeam SONAR bathymetric survey
Bathymetry is the study and mapping of sea floor topography. It involves obtaining measurements of the depth of the ocean and is equivalent to mapping the topography on land. AUS-ROV use multibeam sonars to perform bathymetric surveys on behalf of our clients. Sonar can be used for locating near-surface seamounts and reefs, charting shipping hazards and understanding underwater environments. Engineering companies can use bathymetric data to determine location of subsea cables, oil and gas structures and sea floor pipelines. Often more specialised activities such as searching for missing planes, vessels or other man made objects on the sea floor are carried out. Australia's fishing industry also use bathymetric data to identify possible locations for deep sea fishing. The images below shows sections of bathymetric survey data that was carried out by AUS-ROV using the Norbit iWBMS Multibeam Sonar.
Three-dimensional tunnel and pipeline profiling sonar
AUS-ROV have developed a system for 3D modelling of internal sections of pipelines and tunnels. Our ROV’s integrated with profiling sonar has the ability to produce a 3D model of a tunnel or pipeline, even in zero visibility water.
