Islamic University of Gaza Civil Engineering Department Surveying II ECIV 2332 By B elal A lmassri

Islamic University of GazaCivil Engineering Department

Surveying IIECIV 2332

ByBelal 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 pointsOn 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.

TrilaterationThe 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 SurveyingIt 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 works1. 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.