Jim Gardiner, Paul Newman
21st Century Marine Survey
As we continue our journey through the third decade of the 21st century, it is curious to think what a hydrographic surveyor or oceanographer from 100 years ago would make of the array of technology now at our fingertips. Perhaps there would be more familiarity than you think - the use of sound as a distance measuring tool underwater was then still in its relative infancy, but an echosounder was used to help select the route of a telegraph cable between France and Algeria in 1922 (1).
Now, modern multi-beam echosounders produce tens of thousands of globally positioned depth measurements every second over wide swathes, 3D imaging sonar allow operations in zero visibility, we can position multiple moving or fixed objects underwater, and communicate with underwater vehicles and sensors using acoustic modems. It is, however, important to note that accurate and timely measurements of the sound speed structure through the water column are critical to any acoustic technology and this presents its own set of challenges as we move into the autonomous era.
Our understanding of the structure of the world’s oceans, and the interactions between the atmosphere and bodies of water has been greatly assisted by the ability to make readings of temperature, salinity, sound speed and biogeochemical parameters at depth using sensors that can be fitted to moving vessels, underway winches, autonomous underwater vehicles, and even diving marine predators (2).
The ease and speed by which a position on the surface can now be obtained, even embedded into handheld instruments, in any conditions would likely mystify a surveyor working before even the first artificial satellite was launched. The accuracy of the positions obtained would simply not be believed, but again at least some of the underlying concepts might well have been heard of – a prototype radio direction finding system was installed on a vessel in 1906 (3), the first use of radio navigation by an aircraft was in 1920 (4)
Since then we have seen countless stages of evolution including DECCA-Navigator, Syledis, MicroFix and Trisponder (5) before the deployment of the Global Positioning System and the issue of Selective Availability that led to surveyors developing differential positioning techniques and modern real-time kinematic positioning and the correction services available today.