HYDROGRAPHIC SURVEYING
HYDROGRAPHIC SURVEYING course will provide students with the fundamental knowledge in hydrographic survey including the theory of tides, plan of works, techniques for positioning and sounding, charts production process and also one week practical camp to expose hydrographical survey working environment from
planning to charts production.
planning to charts production.
Intro Hydrographic Surveying
Hydrographic survey is the science of measurement and description of features which affect maritime navigation, marine construction, dredging, offshore oil exploration/drilling and related activities. Strong emphasis is placed on soundings, shorelines, tides, currents, sea floor and submerged obstructions that relate to the previously mentioned activities. The termhydrography is sometimes used synonymously to describe maritime cartography, which in the final stages of the hydrographic process uses the raw data collected through hydrographic survey into information usable by the end user.
Hydrography is collected under rules which vary depending on the acceptance authority. Traditionally conducted by ships with a sounding line or echo sounding, surveys are increasingly conducted with the aid of aircraft and sophisticated electronic sensor systems in shallow waters.
SLIDE POWER POINT : https://drive.google.com/file/d/0B9rxsp2-nmrFdDF3Qlp0aFRQb3M/view?usp=sharing
Tides
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth.
Some shorelines experience two almost equal high tides and two low tides each day, called a semi-diurnal tide. Some locations experience only one high and one low tide each day, called a diurnal tide. Some locations experience two uneven tides a day, or sometimes one high and one low each day; this is called a mixed tide. The times and amplitude of the tides at a locale are influenced by the alignment of the Sun and Moon, by the pattern of tides in the deep ocean, by the amphidromic systems of the oceans, and by the shape of the coastline and near-shore bathymetry
SLIDE POWER POINT : https://drive.google.com/file/d/0B9rxsp2-nmrFQnVYNnFGZEFWT3c/view?usp=sharing
Hydrographic survey planning
The guidelines are intended for use in ports and harbours where hydrographic surveys are carried out to support safe navigation of vessels. They are based on widely accepted good practice for the planning, execution and management of hydrographic surveys.
The guidelines should be used by those responsible for the provision of hydrographic information when determining the hydrographic aspects of risk relevant to the safe navigation of vessels within their jurisdiction.
The guidelines should be used by those responsible for the provision of hydrographic information when determining the hydrographic aspects of risk relevant to the safe navigation of vessels within their jurisdiction.
SLIDE POWER POINT : https://drive.google.com/file/d/0B9rxsp2-nmrFZ2J3cGpTQ01qeFU/view?usp=sharing
PDF : https://drive.google.com/file/d/0B9rxsp2-nmrFZkNxQ0pLaUxtUWM/view?usp=sharing
Positioning
Differential GPS is widely used to fix vessel position during hydrographic suveys. The source of the differential corrections should be proven by comparison with a known survey control point, particularly if a local base station is established. GPS receivers should be configured to output positions in the desired datum (normally WGS84) with associated quality tags. The quality of the position fixes should be monitored during sounding operations through examination of the GPS parameters in use (number of tracked satellites, dilution of precision (HDOP and PDOP), etc), and real-time comparison with a second positioning system is recommended. Post-processed differential is an alternative to RTK in instances where a high accuracy positioning solution is required. Users can navigate with a Satellite Based Augmentation Service (SBAS) such as WAAS while logging raw GPS aboard, and simultaneously at a reference (control) station ashore.
Depths are normally measured using either single-beam (SBES) or multi-beam (MBES) echo sounders. Complete seabed ensonification for the purpose of small target detection can be achieved when these systems are used in conjunction with a towed or fixed side scan sonar system. It should be noted that SBES is still the most common tool used in port and harbour surveys and will continue to give valid results when used correctly in a well planned and executed survey. Multi-transducer, single beam (Sweep) systems are becoming less popular in favour of shallow water, wide swathe or dual head multi-beam sonar systems. However, until capital and operating costs reduce significantly, it is unlikely that, in the short term, MBES will replace SBES for routine surveys in the average port or harbour.
Chart Production Process
Hydrographic data can be presented in a number of formats and styles, depending on its intended purpose. The underlying principle in compiling records of any survey is that they must be entirely intelligible to any person having a sound knowledge of the
type of survey concerned, but not necessarily involved in the survey. A large proportion of hydrographic surveysin ports and harbours will be repeat surveys for a specific purpose, and for specific end users, where extensive reports and deliverables are
not usually required. Nevertheless, a minimum level of information should accompany sounding data, not only to provide the necessary confidence that the data is fit for its intended purpose, but also to allow for its use by end users with differing requirements.
type of survey concerned, but not necessarily involved in the survey. A large proportion of hydrographic surveysin ports and harbours will be repeat surveys for a specific purpose, and for specific end users, where extensive reports and deliverables are
not usually required. Nevertheless, a minimum level of information should accompany sounding data, not only to provide the necessary confidence that the data is fit for its intended purpose, but also to allow for its use by end users with differing requirements.
SLIDE POWER POINT :
PDF :
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