This document discusses hydrographic surveying, which involves measuring underwater physical features essential for marine activities such as navigation and construction. It outlines the importance, applications, and devices used in hydrographic surveying, including echo-sounders, satellite altimetry, airborne lidar, and GPS technology. The report emphasizes the significance of these surveys in providing critical data for safety and planning in maritime operations.

1. Introduction:
Hydrographic surveying or bathymetric surveying
is the survey of physical features present
underwater. It is the science of measuring all
factors beneath water that affect all the marine
activities like dredging, marine constructions,
offshore drilling etc.
In this report, I shall discuss the importance and
applications of hydrographic surveying, the
devices used for the hydrographic survivor, how
do they work and how he uses them.
Importance of Hydrographic Surveying:
Uses of hydrographic surveying are given below:
1. Depth of the bed can be determined
2. Shore lines can be determined
3. Navigation Chart Preparation
4. Locating mean sea level
5. Scouring, silting and irregularities of the bed can be identified
6. Tide measurement
7. River and stream discharge measurement
8. Massive structures like bridges, dams harbors are planned.
HydrographicSurveying

2. The applications of hydrographic surveying:
1. Dock and Harbor Engineering
2. Irrigation
3. River Works
4. Land reclamation
5. Water Power
6. Flood Control
7. Sewage Disposal
Methods of Hydrographic Surveying over History:
Lead lines, sounding poles, and single-beam echosounders methods1. (figure 1)
2. Wire-drag surveying. (figure 2)
3. Modern Surveying (which is discussed in this report – )figure 3
Figure 1- old method Figure 2 - Wire drag method
Figure 3 - Modern method

3. Hydrographic Survivor Job
- Hydrographic survivor’s daily job is basically to
check the depths of the harbor and ensure the
declared depths (the minimum declared depths are
He then produces chartsdepths safe for shipping).
for the pilots to bring the shipping in to the harbor
(see figure 4 that illustrates charts made for Port
Jackson).
- The information obtained from hydrographic
surveying is required to bring up nautical charts which
involve:
1. Available depths.
2. Improved Channels.
3. Breakwaters.
4. Piers.
5. The aids to navigation harbor facility.
Devices Used and how they work:
Devices used in Hydrographic
surveying can be basically divided
into 4 types ):(shown in figure 5
.1-Echo-sounders
It is used to measure the depth to
the seafloor by using the
properties of acoustic waves.
- The principle of echo-sounders is
basic by measuring the two-way
travel time between the acoustic
waves transmitted on sea surface
and those reflected at seafloor.
- The acoustic wave propagates
through sea water at approximately 1,500 m/s. For example, in the case of a measured two-way
travel time being 4 seconds, the water depth is computed as 1,500 × 4 ÷ 2 = 3,000m
Figure 4- Charts made for Jackson port
Figure 5- Types of hydrographic surveying devices

4. Echo-sounders are
classified into two types,
Single-beam Echosounder
(SBES) which can measure
only one point per
acoustic echo wave (echo)
emitted and Multibeam
Echosounder (MBES)
which is capable of
measuring many points of depth over a wide swath area at the same time.
which estimate information about ocean bathymetry.2- Satellite Altimetry
- The principle of the satellite-altimetry bathymetry is to accurately measure
the distance between the satellite and sea-surface height, where this sea-
surface height is argued to approximately represent the geoid surface. If the
height of the satellite is known in the geocentric coordinate system, then
the sea-surface height, which is the distance between earth ellipsoid and sea
surface, can be computed.
to measure water depth by aircraft equipped with laser3- Airborne Lidar bathymetry (ALB)
ranging system instead of survey vessel with systems that produce acoustic waves.
The ALB principle is to generally transmit two types of lasers, a green laser-
and an infrared laser. The green laser can measure the distance between the
aircraft and the sea bottom, while the infrared laser, which is absorbed by
water, measures the distance between the aircraft and sea surface.
- The merits of ALB is that they are quick and safer surveys in shallow-water
areas, when compared with surveying by vessels. Shallow-water areas
measured using traditional echo-sounder methods take much longer,
because the shallower the water, the smaller the ensonified area becomes
and as a result it takes a long time to survey.
4- Global Positioning System (GPS)
The principle behind GPS positioning is similar to that of radio navigation.
- GPS satellites are equipped with very accurate clocks and the signal
transmitter, and GPS receivers on ship can receive the signal transmitted
from GPS satellites.
The distance between a GPS satellite and a receiver can be determine by-
timing the difference between transmitted and receive times.
The receiver position can also be determined by computing the geometric-
relation among the multiple GPS satellites and the receiver at the same
time.