Hydrography is a branch of applied sciences which deals with the measurement and description of the physical features of oceans, seas, coastal areas, lakes and rivers, as well as with the prediction of their change over time.
Hydrography helps to map out water depth, shape, obstructions, and physical features also involves measuring the tide and the currents.
Hydrographic Survey and Topographic Survey are part of the data collection process used during Dredging, Reclamation and maritime infrastructure works to establish the seafloor and subsea conditions and monitor dredging accuracies.
Visakha Marine Surveys has an expert team to execute Single Beam Echo sounding, Multi Beam Echo sounding, Topographic surveys by Total Station, Auto Levelling, GNSS RTK for all kinds of Projects for Dredging, Reclamation, Breakwater construction, environmental studies and etc.
Single Beam Echo Sounding
Single beam Echo Sounding survey is a technique used to measure water depths and create detailed maps of underwater topography. Single beam survey typically involves a single beam echo sounder, which is a device that emits a single sonar beam downward from a transducer fixed on vessel and measures the time it takes for the sound wave to reflect back from the seafloor.
The survey vessel follows predefined survey lines based on the scope of the survey projects, to cover the survey area systematically. As the vessel moves, the echo sounder continuously sends sound pulses and records the time it takes for the echoes to return.
Acquired data will be processed and survey charts will be produced.
Single beam surveys provide a narrow swath of coverage directly beneath the vessel's track line as it moves. It acquires depth measurements along a single line as only one point per ping is recorded.
Single beam surveys can achieve good depth accuracy, but it's influenced by factors like sound velocity variations and vessel motion, Corrections are applied during data processing to enhance accuracy.
Single beam systems can operate effectively at shallow water depths.
Multi-Beam Echo Sounding
Multi-beam echo sounding (MBES) is a technique used in hydrographic surveying and ocean mapping to measure the depth of a water body and create detailed maps of the seafloor. Unlike traditional single-beam echo sounding, MBES employs an array of multiple sonar beams that are transmitted simultaneously in a fan-shaped pattern. This allows for the collection of a much larger amount of data, resulting in higher resolution and more accurate seafloor maps.
The principle behind multi-beam echo sounding is based on the measurement of the time it takes for the sound waves to travel from the sonar device to the seafloor and back. The sonar device emits sound waves in the form of a fan of beams that spread out horizontally as they travel through the water. When the sound waves encounter the seafloor, they get reflected back and are detected by the sonar receiver.
Multi-beam echo sounding (MBES) surveys have several advantages over traditional single-beam echo sounding.
MBES is faster and more efficient mapping of large areas.
MBES surveys provide highly detailed and accurate seafloor mapping due to the ability to collect a large number of depth soundings across a wide area. The multiple overlapping beams capture more data points, resulting in improved resolution and more precise seafloor representation.
By collecting a multitude of soundings, MBES surveys offer higher data density, ultimately increasing the quality of the derived seafloor maps. This is particularly useful for identifying small-scale features.
Topographic Survey
A topographic survey is a detailed mapping process that measures and delineates the shape, elevation, and features of a piece of land or a specific area of interest. It provides accurate and comprehensive data about the physical characteristics of the terrain, including natural and man-made features such as hills, valleys, rivers, roads, buildings, fences, trees, and other elements that influence the land's configuration.
The purpose of a topographic survey is to create a topographic map or plan, which represents the three-dimensional features of the land in a two-dimensional format. The map typically includes contour lines, which connect points of equal elevation, allowing for visualizing the relief and slope of the land.
Specialized equipment, such as Total Stations, GNSS RTK GPS, and Auto Levelling devices are used to collect accurate data.
Topographic data are processed by using specialized software packages like AutoCAD, Terramodel, Trimble business centre.