5. Looking back: A brief history of vessel-mounted ADCPs
In the 19th century, mechanical devices were developed that could interact with the currents, including current meters based on small propellers that could be lowered from a vessel into the water – the faster the propeller rotation, the stronger the current.
One pioneer of mechanical current meters, in the 18th century, was Christiaan Brunings, the multi-talented inventor of a meter to measure flow in the delta of the River Rhine. Vagn Walfrid Ekman was another important figure, creating an ingenious device used mainly for scientific studies in oceans.
Over time, mechanical devices became more sophisticated – and, indeed, similar instruments are sometimes still used today. But deploying them was far from straightforward. They had to be lowered accurately to the relevant depth – and if the current was strong, there was a risk of damage and potential safety concerns.
And if you needed to do anything that required multiple measurements in a short period of time, such as measuring current profiles at different depths regularly throughout a tidal cycle, then you needed more than one vessel. Sometimes more than ten vessels – and their crews, of course – were needed over a very long day.
Current measurement really began to change in the early 1990s, as computers became more portable, enabling the development of a new wave of digital instruments, including ADCPs.
Initially, profiling currents across an area remained a time-consuming business, requiring a number of instruments. These often produced poor data from inadequate software, with results made worse by poor bottom-tracking ability. The equipment typically came from multiple suppliers, whose products were not designed to work together. Electrical and data-connection problems were frequent. A specialist operator was required to handle the equipment and data presentation, adding to personnel costs.
That has all changed. Today, the best vessel-mounted systems on the market allow you to carry out a survey rapidly and accurately using a small, state-of-the-art ADCP, easily attached to the side or bottom of a vessel.