Islamic University of Gaza

Civil Engineering Department

Surveying II

ECIV 2332

By

Belal Almassri

Chapter 10

Horizontal Control Frameworks

- Introduction.

- Method of Horizontal Control.

- Triangulation.

- Trilateration.

- GPS.

- Types of Triangulation systems.

- Hydrographical Surveying.

IntroductionDefinition of horizontal control surveying:

A surveying process which can determine the positions (Horizontal Coordinates) of survey points into a definite element area.

Control Surveying Types:

1. Horizontal Control: Use the horizontal coordinates (E,N) to determine the positions.

2. Vertical Control: Use the vertical elevations to determine the positions.

Method of Horizontal Control:

Traverse Surveying:

The Horizontal control usually involves the measurement of angles and distances for a small project and it may use one or more Traverses into consideration.

Triangulation & Trilatration:

For larger areas, the horizontal control use the triangles and quadrilaterals to achieve the required accuracy.

GPS

Triangulation

This method is based on the trigonometric

proposition when one side and three

angles of triangle are known, the remaining

sides can be determined by the law of sine.

Moreover if the direction of one side is

known it can determine the rest of the

directions.

Base Line

Step 1:

Step 3:

Step 2:

Step 4:

How to choose the control points

On each point you can see at least two

close points.

The angles should be less than 90

degrees.

The points should be at high terrains so it

can be reached easily.

The triangle should be equally sided.

The internal angles should measured by

the theodolite.

Trilateration

The existence of EDM devices made it

more practical to measure the distances

instead of angles.

It is a very similar to the triangulation

method.

The angles can be measured using the

cosine law.

Note: Similar Steps of Triangulation

GPS (Global Positioning System) GPS is a space-based, radio-navigation

system that provides worldwide, all-

weather, three-dimensional position,

velocity, navigation, and time data to both

civilian and military users.

GPS can provide a very accurate digital

map of the highway infrastructure. The

system includes at least 24 satellites in

orbit 19,320 kilometres (12,000 miles)

above the earth and inclined at 55°.

Types of triangulation systems:

Chain of triangles:

1. Simple and fast.

2. Less cost and less accuracy.

3. For thin strip of lands, angles less than

30 degrees are not permitted.

Chain of quadrilaterals

More accuracy here because there is a

potential for double check on the sides

measurement from two triangles.

Central point figures (Wide Area)

For a city or even a country coverage, the

survey points here are relatively linked

with the dense distribution.

Hydrological Surveying

It is a part of survey that includes the

survey works (mapping or setting out) of

water bodies such as oceans, seas, lake,

rivers and etc.

Hydrological Surveying works

1. Location of Rocks.

2. Determination of water volume, flow

and velocity.

3. Determination of mean sea level.

4. Determination of the depth of water.

5. Surveying works for engineering

projects such as dams, channels, bridges

and sea ports.

Hydrological Surveying works. .

6. Contouring Maps for under water

surface.

7. Location of ships.

8. Location of sea property boundaries.

Depth of water:

By rope and height / By rods / By sonic

equipments.