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