This report discusses methods for fixing horizontal control positions in hydrographic surveying, emphasizing their importance and application in determining water depths and coordinates. It outlines various techniques, including the methods of transit & stadia, range and one angle, and two angles from the shore, detailing their advantages and disadvantages. The aim is to highlight the significance of accurate coordinate systems and the processes required for effective hydrographic surveys.

1. (Methods of Shore Observations for
Horizontal position Fixing)
Student Name: Copyright
Class: 4th
Stage
Course Title: Hydrographic Surveying
Department: Geomatics (Surveying) Engineering
College of Engineering
Salahaddin University-Erbil
Academic Year 2019-2020

2. 1
Abstract
This report is about the methods of observations of shore for fixing the horizontal
control position, I will try to explain the hydrographic engineering science within its
advantages and applications and the most common methods that used in hydrography
briefly.
We knew that the depths of the water bodies at various points and will be changed
and unstable so Depths are determined by making sounding which is determining the
depth of water from stationary boat and the positions of sounding can be determined
either from boat from shore or both of them.
If we want to make a survey Project or let's say if a surveyor wants to make a survey
project for hydrographic surveying and an observation for this project so he needs
andequipmentmany techniques many toolssmany processes many preparation
So For establishing horizontal control and vertical control points ,we have many
methods either offshore or onshore or both I mean from boat or from shore or both
consequently I wrote a report about this important t subject and In this report I
mention all methods and explain the three applicable and usage methods that have
been used in hydrographic surveying and also mention which method is good or
better than the other and advantages and disadvantages of these methods .At the end
my aim for preparing this report is to show the importance of hydrographic surveying
and how these methods can be used and all requires and need for these methods and
also mention all steps, all equations that must be used for these methods.
Finally most important point I should mention it is co-ordinate system or finding the
coordinates .the surveyor deals with the coordinates, so we make all these processes,
learning all methods, equations, formulas, steps, establishing control points, all above
just for one purpose which is finding the or calculating coordinate, and the most
important thing in coordinate is accuracy, avoiding from errors and uncertainty.

3. 2
Table of contents
Contents page
Abstract.......................................................................................................................... 1
Table of contents ........................................................................................................... 2
Chapter one - Introduction ............................................................................................ 3
1.1.Overview of Hydrographic surveying.................................................................. 3
1.2. Methods of locating Sounding are ...................................................................... 4
Chapter two- Background and Review ......................................................................... 5
Chapter Three- Methods................................................................................................ 6
3.1.method of transit & stadia (tacheometer(............................................................. 7
3. 2.Method of range and one angle:.......................................................................... 9
3.3.Method of two angles from the shore ................................................................10
Chapter Four- Conclusion ...........................................................................................13
Chapter Five- References ............................................................................................14

4. 3
Chapter one - Introduction
1.1. Overview of Hydrographic surveying:
Hydrographic surveying (also known as a bathymetric survey) is one of the oldest
forms of marine research, and comprises a process of collecting depth information
that can be used in developing and maintaining nautical charts. In essence, a
hydrographic survey collects depth, position and time data, which can be used to
create a model of the seabed so Hydrography is Branch of science that deals with the
measurement of bodies of water and Deals with the physical features of the navigable
portion of the earth’s surface and adjoining coastal areas and Sounding measurement
of depth below the water surface. The method starts by locating special control points
along the shore line. The sounding method is employed to determine the depth at
various points by means of stationary boats. Sounding locations can be either made
from boat to the control points or by fixing a point in the boat and taking sounding
from the control point. Before this procedure certain preliminary steps have to be
made:
1. Reconnaissance
2. Locate Horizontal Control
3. Locate vertical Control
Mainly we have horizontal fixing positions and vertical fixing positions So the
methods of observations from the shore for horizontal position fixing are:
1. Method of transit and stadia (tachometer).
2. Method of Range and one angle.
3. Method of two angles from the shore.

5. 4
As I mentioned we have horizontal fixing positions and vertical fixing positions for
the horizontal fixing positions there are many methods of locating the soundings
1.2. Methods of locating Sounding are:
1.2.1. From the shore:
A. Location by Cross-Rope.
B. Location by two angles from the shore.
C. Location by Range and One angle. From the shore.
1.2. 2.From the boat:
A. Location by two angle from the boat.
B. Location by Range and One angle from the boat.
1.2.3. From both (the shore and the boat):
A. Location by One angle from the shore and from the boat.
B. Location by Range and Time Intervals of the boat.
C. Location by Intersecting Ranges.
D .Location by Tachometric Observations.

6. 5
Chapter two- Background and Review
On the day Hydrographic surveying is getting increasingly advanced. In the past,
measurements had to be taken by hand – dropping lines into the water and bringing
back spot results. Now, specialized water vessels with sonar equipment on board are
most commonly used, and in some cases low-flying aircraft are also used. The size of
the vessel depends on the size of the area being surveyed, as well as the depth of the
water – for deep ocean surveys a large ship is often used, whereas areas closer to the
shore may even use inflatable rafts. In my particular case, we were on board a boat.
On board we had access to two types of sonar equipment – sides can and multiband
sonar. Combined, these two forms of sonar (an acronym for sound navigation
ranging), provide a detailed look at the surface below the water. Sonar works by
sending sound waves to the bottom of the ocean floor and bouncing them back up to
the vessel. The echo of that sound wave is then measured to give a depth in that
particular area. A huge amount of measurements need to be taken – so it’s no easy
task! Several scans are taken per square foot, so it can take several days or even
weeks to cover a significant area.

7. 6
Chapter Three- Methods
As I mentioned above that we have horizontal control and vertical control position so
Locating Horizontal Control for hydrography is often based on preexisting geodetic
control. When it is unavailable or insufficient the hydrographic surveyor must
establish his own horizontal control network or supplemental control stations. The
accuracy requirements for horizontal control for hydrography are not as strict as those
for land surveys. The IHO (Special Publication No. 44) suggests some minimum
accuracy standards and gives some general specifications in order to achieve these
standards.so control is necessary to locate all features of the land and marine in true
relative positions. Hence a series of lines whose lengths and azimuths are determined
by means of either triangulation or any other methods.
Let's Have Quick look for these figures which are a principal of work for
Hydrographic Surveying in General:
Figure1: hydrographic surveying Figure 2: hydrographic surveying

8. 7
There are three methods from shore so let's mention and explain them briefly:
3.1. Method of transit & stadia (tachometer):
Tachometer is the optical instrument for level the stadia measurement memes
distance measurement.
Location by Tachometric Observations Method is very much useful in smooth
waters. Position of the boat is located by tachometric observations from the shore on
a staff kept vertically on the boat. Observing the staff intercepts at the instant the
sounding is taken, the horizontal distance between the instrument stations and the
boat is calculated by : Direction of the boat (P) is established by observing the angle
(α) at the instrument station (B) with reference to any prominent object so this
method This method is very much usable in smooth waters Position of the boat is
located by tachometric observations from the shore on a staff kept vertically on the
boat Observing the staff intercepts at the instant the sounding is Taken the horizontal
distance between the instruments stations and the boat is calculated by Direction of
the boat( p) is established by observing the angle a the instrument station (B) with a
reference to any prominent object (A).
The equation and figure are shown below:
𝐴𝑍𝑠1 = 𝐴𝑍 𝐴𝐵 + 90………… (1)
𝐸 𝑎1 = 𝑆1 + 𝑠𝑖𝑛𝐴𝑍𝑆1………… (2)

9. 8
Figure 3: Stadia Method
This method has many Advantages which are:*
Easy to use.-
Accuracy depends on the distance.-
Not expensive.-
Is simple-
Used to find direction.-
Not need much time.-
Also this method has many Disadvantages which are:*
-It is a difficult method because of movement of the boat.(and to solve this we use the
flot rope which is the easiest way to elimuminate errors).-
It is not used for Long Distance more than 200m.-

10. 9
3. 2.Method of range and one angle:
In this method, boat is kept in range line with the help of two signals on the shore.
The boat is moved and the point where sounding is measuring is observed by the
theodolite or sextant and angle is noted. Using this angle, we can fix the point in the
range.
Likewise, all other soundings are observed from different stations. The angle should
be more than 30 degrees otherwise fix should be poor.so, whenever the angle is less
than 30o
, new instrument station is selected. This method is so accurate and easy for
plotting the sounding details, and its formula with its figure are shown below:
tanα1 =
S1
d
………………… (3)
S1 = d. tanα1……………… (4)
Na1 = NA + S1……………………… (5)
Ea1 = EA + S1……………. (6)
Figure 4: Range and one Angle Method

11. 10
*This method has many Advantages which are:
Easy to do.-
More accurate and pricise than previous method.-
Used for long range.-
But also has disadvantages that are:*
It is difficult to design.-
More Advanced.-
-More time needed.
Many angles are required.-
Needs many calculations.-
3.3. Method of two angles from the shore:
In this method, two instrument stations are fixed on the shore with proper distance.
Two instruments and two instrument men are required to do this job. From the two
instrument stations, angular observations are made and a point is located where
sounding is measured.
then new instrument station is)0
30(ent is less thanIf the angle made by instrum
selected. In this case, primary setting out and erecting range signals are eliminated.
This method is useful when water currents are strong and difficult to row the boat
along range line so
Location by two angles from the shore is a point is fixed independent of the range by
angular observations from two points on the shore. Used to locate some isolated
points. Two instruments & two surveyor are required & instrument is selected with
accuracy. If (A & B) are two instrument station and( ‘d’) is measured accurately.
Instrument stations A and B are precisely connected to the ground and their positions
on plan are known.

12. 11
Methods of Locating Sounding to the ground and their positions on plan are known.
Surveyor on the boat holds a flag for a few seconds, and on the fall of the flag the
sounding and the angles are observed Simultaneously. co-ordinates of the position (P)
method is used when it isthisof the sounding may be computed from the relations
sible to keep the sounding boat on a fixed range line. The method requires twonot pos
on the shore)A and B(theodolites. The instruments are set up at two known stations
, whose location is required, horizontal angles)P1(the sounding boat is atline. When
.The time at which the sounding is)α1 and α2(th the instruments measured asat bo
-.The cois also measured)and BA(betweentaken should be noted. The distance d
tan α1+ tan/ (=d tan α2relationsmay be computed from the)P1(pointordinates of
:its formula and figure shown below.tan α1+ tan α2)/ (α1.tan α2=d tan) yα2
∆𝑋 =
𝑑.𝑡𝑎𝑛𝛼2
𝑡𝑎𝑛𝛼1+𝑡𝑎𝑛𝛼2
…………………… (7)
∆𝑌 =
𝑑.𝑡𝑎𝑛𝛼1+𝑡𝑎𝑛𝛼2
𝑡𝑎𝑛𝛼1+𝑡𝑎𝑛𝛼2
…………………………. (8)
Figure 5: Range and Tow Angle Method

13. 12
This Method has the following advantages:*
- Preliminary work of setting out and erecting range signals is eliminated.
- Suitable for strong current of water due to which it is difficult to row the boat a1on
the range line
Flexibility in distrbution from shore control points.-
Flexible for the positions that have high relief.-
Also it has many disadvantages which are:*
-because we have 2 angle measurement so more error may occurs.
It is difficult to read some Angles one moment.-
Needs more time.-
Needs more practicable staff.-
-It needs pre-designed work which means it is difficult to get the same angle as
designed.
We have to avoid more observations in hydro to get more accurate results.-

14. 13
Chapter Four- Conclusion
Hydrographic surveying is an important part or important science in our life we
mentioned that and we saw that horizontal and vertical fixing positions are the most
important things in this science Consequently i talked and explained one of these
methods , So nowadays we need this important science with all its methods,
processes, and all components and contents of it As I told the most important thing
for Surveyor is (coordinates system) and we can get these coordinate system which
is( Easting and northing and elevation)(E,N,Elevation) via many methods within
many conditions and situations and as I explained the methods from the shore that
have been used in hydrographic surveying to calculate (E,N) and each method will be
used within a specific condition and satiation I mean depends on its situation and
circumstances and under many conditions.
The method of Horizontal Fixed Position from the shore by using this method we
can make surveying and observation and fixing the positions and then using them as
the control points in order to get coordinates So the three above methods have
advantages and disadvantages and i explained them briefly.

15. 14
Chapter Five- References
1. https://www.slideshare.net/gokulsaud/hydrographic-survey-for-std-not-print
2. https://slideplayer.com/slide/12744517/
3. http://stream1.cmatc.cn/pub/comet/MarineMeteorologyOceans/IntroductiontoHydrography/
comet/oceans/hydrography/references.htm
4. https://theconstructor.org/surveying/methods-locating-sounding-hydrographic-
surveying/19976/#:~:text=By%20Range%20and%20One%20Angle%20from%20the%20Sh
ore,the%20point%20in%20the%20range.
5. https://pdfs.semanticscholar.org/c4ae/b558db7ea7a7017bb07558c336ab580b1fdc.pdf
6. https://pdfs.semanticscholar.org/c4ae/b558db7ea7a7017bb07558c336ab580b1fdc.pdf
7. https://theconstructor.org/surveying/hydrographic-surveying-methods-uses/13838/