Hydrographic survey

VOCABULARY

hydrographic survey – гидрографическая съемка

oilfield – нефтяное месторождение

magnetic variation - магнитное склонение

state of the art of measurement equipment – уровень измерительного оборудования

vertical reference - вертикальный ноль глубин

thin out the data – разрежать, уменьшать количество данных

correct –вносить поправки

dredging – дноуглубительные работы

sub-decimetre менее дециметра

land features – особенности рельефа, береговые ориентиры

heave - вертикальное перемещение судна под воздействием волн

process – обрабатывать (данные, информацию)

accuracy – точность

which can offer substantial productivity gains – которая может быть очень результативна в мелкой прозрачной воде.

Find the answers to these questions in the following text:

1. What does hydrographic survey include?

2. Does hydrographic survey describe aids to navigation?

3. Why is water level observed in the course of the survey?

4. Why is it important to study the sea floor material?

5. How is hydrographic data now collected and processed?

6. What equipment does the modern surveying rely on?

7. What contributes to the best results in hydrographic surveying?

Hydrographic survey in its strictest sense is the process of gathering information about navigable waters for the purposes of safe navigation of vessels. It applies to survey of any navigable waters, including lakes and rivers, but it is most commonly applied to marine navigation.

The term may be more broadly used for data gathering exercises for the purpose of describing the seafloor for a variety of purposes, e.g. the largest hydrographic community is globally involved in the description of offshore oilfields.

Hydrographic surveying is an age-old art of collecting soundings and other data which is used to make charts and other navigational aids used by seafarers.

• Taking soundings - measuring water depths - is the most basic operation of hydrographic surveying..

• Tide or water level measurements are also recorded to provide a vertical reference (e.g. Mean Lower Low Water) for water depths.
• In addition to delineation of coast lines and measurement of submerged features, a hydrographic survey usually includes measurement of magnetic variation, currents, and meteorological elements.
• In the course of surveying it is essential to precisely determine positions of all detected water and land features, as well as aids to navigation. The capability to position the data precisely in the horizontal plane has been increased enormously by the availability of satellite positioning systems, particularly when augmented by differential techniques. This advance in technology has been particularly significant since navigators are now able to position themselves with greater accuracy than that of the data on which older charts are based.

It should be noted, however, that the accuracy and completeness of a hydrographic survey cannot currently reach that of land mapping, owing to technological limitations of imaging systems.

• Of additional concern to most surveys is the nature of the sea

floor material (i.e. sand, mud, rock) due to its implication for

anchoring, dredging, structure construction, pipeline and cable

routing and fisheries habitat.

All hydrographic data is now collected and processed with specialized computer systems. After data is collected, it has to undergo post-processing. A massive amount of data is collected during the typical hydrographic survey, often several soundings per square foot. Depending on the final use (navigation charts, Digital Terrain Model, volume calculation for dredging, topography, bathymetry) this data must be thinned out.

It must also be error corrected (bad soundings,) and corrected for the effects of tides, waves/heave, water level and water temperature differences (thermoclines.) Final output of charts is created in charting software.

The state of the art of depth measurement equipment has been evaluated by the IHO as follows:

a) Single beam echo sounders have reached a sub-decimetre accuracy in shallow water. The market offers a variety of equipment with different frequencies, pulse rates etc. and it is possible to satisfy most users' and, in particular, hydrographers' needs.

b) Side scan sonar equipment technology has also reached a high level of bottom obstacle detection and definition. Although, at present, its use is limited by the low speed (5-6 knots maximum) at which it can be operated, it is widely employed for harbour and navigable channels surveys to ensure obstacle detection between the measured survey lines. Many hydrographic agencies consider its use compulsory in such areas, often prescribing overlaps of 100% or more.

c) Multi-beam echo-sounder technology is developing rapidly and offers great potential for accurate and total seafloor search if used with proper procedures and provided that the resolution of the system is adequate for proper detection of navigational hazards.

d) Airborne laser sounding is a new technology which can offer substantial productivity gains for surveys in shallow, clear water. Airborne laser systems are capable of measuring depths to 50 m or more.

The equipment can be installed on small craft, AUVs (Autonomous Underwater Vehicles), or UUVs (Unmanned Underwater Vehicles). Laser measuring systems can be on a helicopter or an aircraft. Surveys of offshore areas require a large and properly equipped vessel, as well as a staff of qualified hydrographic surveyors

Best results are achieved in hydrographic surveying when the appropriate procedures and equipment are used in conjunction with the expertise and training of the hydrographic surveyors.

ASSIGNMENT

1. What word does not fit the others?

Vehicle draft ship craft

Precise accurate approximate exact

Seafloor bottom seabed flooring

Rapidly fast quickly slowly

2.Read and translate the following words. Consider the different stress in nouns and verbs:

Verbs	Nouns
Pro’cess	‘Process
Sur’vey	‘Survey
Con’duct	‘Conduct
Im’port	‘Import

3.Match the words with their short definitions:

1. Reference datum

2. Aids to Navigation

3. Depth

4. Submerged.

5. Accuracy

a. The vertical distance from a given water level

to the bottom.

b. Buoys, beacons, fog signals, lights, radiobeacons, leading marks,

and other devices serving the interests of safe navigation

с. A general term applied to any datum, plane, or surface used as a reference or base from which other quantities can be measured.

d. Under water; not showing above water.

The opposite is.uncovered..

e. The degree of closeness of a variable to its true value

4. Read the text. Fill the lettered spaces with the correct words given below the text. One word is odd.

SURVEY

Hydrographic data is collected a. …. and positioning the data so that it may be accurately charted. Hydrographic data will include b. … of use to navigators as well as information about the water and с ….

Surveys are most commonly d. …out by or under the supervision of national organizations with responsibility for chart making and distribution. Coordination of those organizations is e. …by the International Hydrographic Organization.

1. bottom
2. shore features
3. under strict rules for evaluating
4. carried
5. produced
6. conducted

5. Scientists must make conclusions. To do this they often use a syllogism. Syllogism contains three statements: two premises and one conclusion.

Look at the following example of a syllogism:

1. Echo sounders with high frequency are used for surveying shallow waters.
2. This echo sounder has very high frequency.

Conclusion: Therefore, this echo sounder is intended for surveying shallow waters.

We can change the syllogism to a formula:

All “A” are “B”

“C” is “A”

Therefore, “C” is “B”

Complete the syllogisms below.

1. All depths within the area have been obtained by sweeping.
2. The depth over the shoal is in this area.

Conclusion: …

1. Most standards established by IHO concern hydrographic matters.
2. The standards included in this manual were established by IHO.

Conclusion: …

1. Most hydrographic requirements depend upon depths.
2. Between line requirements are hydrographic requirements.

Conclusion: …

Translate the sentences:

1. Измерение глубин – одна из важнейших задач

гидрографической съемки.

2. Гидрографическая съемка обычно включает измерение

магнитного склонения.

3. В ходе съемки очень важно точное позиционировать все

Обнаруженные особенности рельефа дна.

4. Судоводители могут определить свое местонахождение с

большей точностью, чем точность старых карт.

5. Дифференциальная спутниковая система позиционирования

дает возможность точно

определить местоположение всех данных.съемки.

6. Приливный уровень является нулем глубин

7. Дополнительный интерес для гидрографа представляет

материалы морского дна (песок, ил и т.д.)

Fill the blanks in the sentences with the appropriate word. Rewrite and translate the sentences:

large

clear

basic

amount

attenuated

main

detected

Measuring water depths - is the most …. operation of hydrographic surveying.

It is essential to precisely determine positions of all … aids to navigation.

Airborne laser sounding is a new technology which can offer substantial productivity gains for surveys in shallow, … water

A massive …. of data is collected during the typical hydrographic survey

Surveys of offshore areas require a … and properly equipped vessel

The …. beam is directed perpendicular from the transducer.

The received echo signal is basically an … copy of the short transmit pulse.

Дата добавления: 2015-11-16