Hydrographic survey is that branch of surveying which deals with the measurements of bodies of water

3. WHAT IS HYDROGRAPHIC SURVEYING?
 Hydrographic survey is that branch of surveying
which deals with the measurements of bodies of
water.
 It is the art of delineating the contour and features of
seas, river , lakes and submarine levels.

4. OBJECTIVE OF HYDROGRAPHIC
SURVEYING:
Measurement of tides for sea cost work
EXAMPLE:
Construction of sea defence works, harbours etc.
The establishment of levelling datum and for reducing sounding.
Measurement of quantity of water and flow of water in connection
of water schemes.
Power scheme and flood controls.

5. STEPS IN HYDROGRAPHIC SURVEYING:
There are two steps involved in hydrographic
surveying:
1.Horizontal controls
2.Vertical controls

6. HORIZONTAL CONTROLS:
In an extensive survey, the primary horizontal control is
established primary horizontal control secondary once by
running theologize and tape traverse.
For rough work, the control may be established by
running a theologize and stadia traverse or plane table
trader.

7. STADIA SURVEYING:
The distance are determined by angles.
There are stadia hairs from which angles are
determined without change.

8. VERTICAL CONTROLS:
These are based upon a series of bench mark
established near the shore line by spirit levelling and
these serve for setting and checking tide gauges etc to
which the sounding are referred .

9. METHODS OF HYDROGRAPHIC
SURVEYING:
SOUNDING:
The measurement of depth below the water surface is
called sounding.
 sounding is the main operation is hydrographic surveying.
To take the soundings vertical control is necessary , a
horizontal control is necessary to locate the sounding.

10. PURPOSE OF SOUNDINGS:
Soundings are required for,
Making nautical charts for navigation.
Measurement of areas subject to scour or silting and
to ascertain the quantities of dredged material.
Making sub-aqueous investigations.

11. INSTRUMENTS NEEDED:
The equipments needed for soundings;
sounding boat
Sounding rods or poles
Lead lines
Sounding machine
Fathometer

12. SOUNDING BOAT:
A new-boat for sounding should be sufficiently roomy
and stable.
For quiet water, a flat bottom boat is more suitable,
but for rough water round- bottomed boat is more
suitable.
For regular soundings, a row boat may be provided
with a well through which soundings are taken.

14. SOUNDINGS RODS OR POLES:
A sounding rod is a pole of a sound straight-grained well
seasoned tough timber usually 5 to 8 cm in diameter and 5
to 8 meters long.
They are suitable for shallow and quiet waters. An arrow
or lead shoe of sufficient weight is fitted at the end.
This helps in holding them upright in water. A pole of 6m
can be used to depth upto 4 meters.

16. LEAD LINES:
A lead line or a soundings line is usually a length of a such
cord, or tiller rope of Indian hemp or braided flax or a
brass chain with a sounding lead attached to the end.
The line should be kept dry when not in use. It should be
soaked in water for about one hour before it is used for
taking soundings.
The length of the line should be tested frequently with a
tape.

17. For regular soundings, a chain of brass, steel or iron is
preferred. Lead lines are usually used for depths over
about 6meters.
Sounding lead is a weight (made of lead )attached to the
line. The weight is conical in shape and varies from 4 to
12 kg depending upon the depth of water and the strength
of the current.
The weight penetrates in the mud and stops where the
board strikes the mud surface.

19. SOUNDING MACHINE:
Where much of soundings is to be done, a sounding
machine as very useful.
The sounding machine may either be hand driven or
automatic.
The readings are indicated in two dials. The outer dial
showing tenths of a foot.
A handle is used to raise the level which can be
suspended at any height by means of a paul and
ratchet.
The sounding machine is mounted in a sounding boat
and can be used up to a maximum depth of 100 ft.

21. FATHOMETER:
A fathometer is used for ocean sounding where the
depth of water is too much.
ECHO-SOUNDING is adjusted to read depth in
accordance with the velocity of sound in the type of
water in which it is being used.

23. The main parts of an echo-sounding apparatus are:
Transmitting and receiving oscillators
Recorder unit
Transmitter/ power unit
If the speed of sound in that water is v and the time interval
between the transmitter and receiver is t, the depth h is given by,
h=vt/2

25. METHOD OF LOCATING SOUNDINGS:
 BY CONNING THE SURVEY VESSEL:
1.By cross rope.
2.By range and time intervals.
 BY OBSERVATION WITH THEODOLITE:
1.By range and one angle from the shore.
2.By range and one angle from the boat.

26. 3.By two angles from the shore
4.By two angles from the boat.
5.By one angle from shore and one from
boat.
6.By intersecting ranges.
7.By tachometry.
BY THEODOLITE ANGLES AND EDM
DISTANCE FROM THE SHORE.
BY MICROWAVE SYSTEMS.

27. BY CONNING THE SURVEY VESSEL:
The process of keeping the survey vessel or boat on a
known course is known as CONNING THE VESSEL.
One of the most common method of conning is to fix markers(poles,
beacons etc..,) on the shore.
This method is suitable for work in rivers and open
seas up to 5km off shore.

28. o RANGE:
1.A range or range line is the line on which
soundings are taken.
2.The range lines are laid perpendicular to the shore
line and parallel to each other.
o SHORE SIGNALS:
1.Signals can be constructed in variety of ways.
2.The most satisfactory and economic type of signal
is a wooden tripod structure dressed with white
and coloured signal of cloth.
3.The position of the signals should be located very
accurately since all the soundings are to be located
with reference to these signals.

29. 1.LOCATION BY CROSS – ROPE:
This is the most accurate method of locating the soundings and
may be used for rivers , narrow lakes and for harbours.
It is also used to determine the quantity of materials removed
by dredging , the soundings being and after the dredging work
is done.
A single wire or rope is stretched across the channel and is
marked by metal tags .
The soundings are then taken by weighted pole.

30. 2.LOCATION BY RANGE AND TIME
INTERVALS:
In this method , the boat is kept in range with the two
signals on the shore and is rowed along it at constant
speed.
In this method soundings are taken at different time
intervals.
The method is used when the width of channel is small
and when great degree of accuracy is not required.

31. BY OBSERVATIONS WITH THEODOLITE:
1.LOCATION BY RANGE AND ONE ANGLE FROM THE
SHORE:
In this method , the boat is ranged in line with the two shore
signals and rowed along the ranges.
The point where sounding is taken is fixed on the range by
observation of the angle from the shore.
If the angle at the sounding point (say angle is β) is less than
30°, the fix becomes poor.

32. The nearer the intersection angle (β) is to a right angle, the
better.
The only defect of the method is that the surveyor does
not have an immediate control in all the observations.
In order to avoid acute intersections, the lines of
soundings are previously drawn on the plan and suitable
instrument stations.

33. 2.LOCATION BY RANGE AND ONE ANGLE
FROM THE BOAT:
The boat is kept in range with the two shore signals and is
rowed along it.
At the instant the sounding is taken, the angle , subtended
at the point between the range and some prominent point
on the shore is measured with the help of the sextant.
Then the telescope is directed on the signals , and the side
object is brought into coincidence at the instant the
sounding is taken.

34. ADVANTAGES:
 Since all the observations are taken from the boat, the surveyor has
better control over the operations.
 The mistakes in booking are reduced since the recorder books the
readings directly as they are measured.
 On important fixes , check may be obtained by measured a second angle
towards some other signal on the shore.
 To obtain good intersections throughout, different shore objects may be
used for reference to measure the angles.

35. 3.LOCATION BY TWO ANGLES FROM THE
SHORE:
In this method ,a point is fixed independent of the range
by angular observations from two points on the shore.
The method is generally used to locate so isolated points.
Two instruments and two instruments men are required.
New instrument stations should be chosen when the
intersection angle(θ)falls below 30°.

36. ADVANTAGES:
The initial work of setting out and erecting range
signals is eliminated.
It is useful when there are strong currents due to
which it is difficult to row the boat along the range
line.

37. 4.LOCATION BY TWO ANGLES FROM THE
BOAT
 In this method , the position of the boat can be located by the
solution of the three point problem.
 The three shore points should be well- defined and clearly
visible.
Prominent natural objects such as church spire, lighthouse,
flagstaff, buoys etc.., are selected for this purpose.
This method is used to take soundings at isolated points.

38. 5.LOCATION BY ONE ANGLE FROM THE
SHORE AND ONE FROM THE BOAT:
This method is the combination of methods
location by two angles from the shore and
location by two angles from the boat.

39. 6.LOCATION BY INTERSECTING RANGES
This method is used when it is required to determine by
periodical soundings at the same points.
This method is very essential on the harbours and
reservoirs.
The position of sounding is located by the intersection of
two ranges, thus completely avoiding the angular
observations.

40. The boat is rowed along a range perpendicular to the
shore and soundings are taken at the points in which
inclined ranges intersect the range.
The position of the range poles determined very
accurately by ground survey.

41. 7.LOCATION BY TACHOMETRIC
OBSERVATIONS:
This method is very useful in smooth waters.
The position of the boat is located by tachometric
observations from the shore on a staff kept vertically on
the boat.
The horizontal distance between the instrument stations
and the boat is calculated by,
d=(f/i)s+(f+d)

42. The transit station should be near the water level so
that there will be no need to read vertical angle.
The method is unsuitable when soundings are taken
far from shore.

43. PURPOSE OF HYDROGRAPHIC
SURVEYING:
Purpose of navigation and water supply
Harbour works or for determination of discharge of
streams
Photographic survey of shores and banks
Marine construction
Dredging
Offshore oil exploration /offshore oil drilling

44. USES OF HYDROGRAPHIC SURVEYING:
Used for making nautical charts.
Used for establishing mean sea level and observations of tides.
Used for measurements of discharge of rivers.
Used for controlling and planning of engineering projects.
Used for determination of shore line.

45. The location of light rocks sand balls,
buoys(anything that floats on the surface of water).
Hydrographical survey are made to a quire and
present data on ocean , lakes , harbours .

46. SOURCES:
Nautical charts are based on hydrographic surveys.
As surveying is laborious and time consuming,
hydrographic data for many areas of sea may be dated
and not always reliable.
Depths are measured in a variety of ways.

48. NAUTICAL CHARTS
A nautical chart is a graphic representation of a
maritime area and adjacent coastal regions.
Depending on the scale of the chart, it may show
depths of water and heights of land(topographic map),
natural features of the seabed, details of the coastline ,
navigational hazards , locations of natural and human
made aids to navigation , information on tides and
currents , local details of the Earth’s magnetic field ,
and manmade structures such as harbours , buildings
and bridges

49. Nautical charts are essential tools for marine
navigation.
Nautical charting may take the form of charts printed
on paper or computerized ELECTRONIC
NAVIGATIONAL CHARTS.

50. DEPTHS AND HEIGHTS:
Depths which have been measured are indicated by
the numbers shown on the chart.
Depths on charts published in most parts of the world
use METRES.
Older charts , as well as those published by the united
states governments , may use feet or fathoms.

51. Depth contour lines show the shape of underwater .
Depths are measured from the chart datum, which is
related to the local sea level.

53. THANK
YOU!!!