Hydrographic surveying in Australia is the survey of physical features found underwater. It can be defined as the science of measuring different factors beneath the water that have a substantial effect on marine activities such as marine constructions, dredging and offshore drilling. This type of surveying is mainly conducted under authority concerns. Hydrographic survey is mainly carried out using sounding, sensors or electronic sensor systems for shallow water. Data obtained from this type of surveying is needed to bring up nautical charts that involve improved channels available depths, piers, breakwaters and aids to navigation harbour facility.
The survey can also take part in the necessary collection of data relating to developments and constructions of port facilities.
Applications
There are different types of applications for hydrographic survey. These applications include irrigation, river works, dock and harbour engineering water power, land reclamation flood control, sewage disposal and many more.
Uses
Hydrographic survey has a lot of uses that may include determining shorelines, determining the depth of the bed, preparing navigation charts, measuring direct currents to locate sewer fall, locating mean sea level, tide measurement, silting, scouring and irregularities of the bed identification, stream and river discharge measurement, planning massive structures such as dams and bridges.
Preliminary steps involved
The method of the hydrographic survey in Australia starts by locating special points of control along the shoreline. Determining the depth at different points using stationary boats is done using the sounding method. From hydrographic surveying definition that we gave you earlier in this article, we talked about sounding being one of the methods. Sounding locations can be made by fixing a point in the boat or from boat to control points. Before going on with this procedure, some preliminary steps need to be carried out such as locating vertical control, locating horizontal control and reconnaissance.
Reconnaissance
Every project requires a start-up plan. It is, therefore, necessary to do reconnaissance. This is to help in choosing the best way of doing the survey. This is also important in facilitating the satisfactory completion of the survey according to the requirements and specifications that govern such work. It is, therefore, necessary to take aerial photographs to help in the study.
Locating horizontal control
It is also necessary to locate the horizontal control to be able to locate all marine and land features in true relative positions. Methods such as triangulation are used to determine a series of azimuths and lengths. Plane table and tachometric survey can be done to undergo rough works. There are no rules involved in establishing horizontal controls.
Locating vertical control
Locating vertical control is also an important step in hydrographic surveying in Australia. Establishing of vertical control is necessary before sounding is done. A lot of benchmarks are put in order to serve as vertical control. Checking and setting the levels of the gauges are some of the benchmarks uses. Sounding is typically the process of determining depth below the water. Before undergoing sounding, determining the mean sea level is done. In our next article, we shall talk about the specific need for sounding.
