Islamic University of Gaza Civil Engineering Department Surveying

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. -

Introduction Definition 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.

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 2: Step 3:

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 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, radionavigation system that provides worldwide, all-weather, threedimensional 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. 2. 3. 4. 5. Location of Rocks. Determination of water volume, flow and velocity. Determination of mean sea level. Determination of the depth of water. Surveying works for engineering projects such as dams, channels, bridges and sea ports.

Hydrological Surveying works. . Contouring Maps for under water surface. 7. Location of ships. 8. Location of sea property boundaries. 6. Depth of water: By rope and height / By rods / By sonic equipments.