May 22, 2012
Acoustics in Hydrographic Surveying
Math affects our lives in sometimes the simplest of ways. If you’ve ever rode on a boat you probably don’t think about the thousands of years of innovation that made it possible. Hydrographic surveying basically maps out the depth and floor of the ocean or any other body of water. It is very important to know the depths of the water a boat is sailing on so that they can safely pass. Ever since larger boats came in to use, depths were measured simply with sticks. Obviously this wasn’t very practical and eventually, as technology advanced, people progressed to what is called a lead line. This method has been used for the last thousand years, essentially it was a long rope with a piece of lead attached. The high density of lead ensured it would sink completely. After the lead hit the bottom, the rope would be measured. Measurements couldn’t encompass a large area, because like land the ocean floor has many mountains and valleys, so depths would have to be gathered about every half a mile and then would be put in a chart or map. Most of these measurements, of various countries were gathered by the British, whose empire was very vast at the time. An example of one of these maps is Map A which is an Antique Nautical Navigation Chart, of Rockport Harbor in Massachusetts, this map was made in 1859. On the map there are various numbers scattered, each refers to the depth of the ocean at that particular spot measured using lead lines. Obviously it was a challenge, because they would have to sail to each spot and measure the depth and record it accurately, but at the time it was the only way to ensure safe sailing.
It wasn’t until World War I, when man started studying acoustic principles for war craft, that RADAR (RAdio Detection And Ranging) was discovered. Radar was developed for air only as a way to determine the distance of particular object or any surface. The same technology was then applied in...