TG4-CIE112.pdf - CIE 112 - Fundamentals of Surveying...

CIE 112 - Fundamentals of Surveying
Teachers’ Guide Module #4
Name:
_____________________________________________________
____________
Section: ____________ Schedule:
________________________________________
Class number:
_______
Date:
________________
This document is the property of PHINMA EDUCATION
1
Lesson title: Earth’s Curvature and Refraction
Lesson Objectives:
At the end of this module, you will be able to:
1. Apply the earth’s curvature and refraction correction.
2. Determine whether it is an obstruction or a clearance
at a certain point according to the line of sight.
Materials:
Calculator, Pen, Paper
References:
Roy, S.K. (1999). Fundamentals of
Surveying . New Delhi: Prentice
Hall of India Private Limited
Schofield, W. & Breach, M.
(2007). Engineering Surveying.
Burlington, Canada: Elvesier Ltd
}
A. LESSON
PREVIEW/REVIEW
1) Introduction (2 mins)
Have you ever tried mountain climbing or experienced to be on the top of a tall building?
If you already did, you could say that as you go higher your line of sight will extend to the
horizon. It is due to the earth’s curvature that conceals the view but already seen as you
go to a higher altitude. On the other hand, refraction of light is the bending of light
downwards as it passes through different layers of air with varying densities. When
measuring short distances, these effects can be neglected but working with surveys in long
sights requires these two to be considered. Because errors yielded from these phenomena
increases with distance. For precise work these errors need to be calculated and corrections
will be applied for accurate data.
Due to the curvature of the earth, the points of measurement appear to be lower than
they actually are. In refraction of light, the points appear to be higher than the actually are.
The effect of curvature is always greater than that of refraction. Thus, the combined effect
of these two causes the points of measurement to be lower than its true quantity.
2) Activity 1: What I Know Chart, Part 1 (3 mins)
What I Know Questions: What I Learned (Activity
4)
Research using different means of resources. Learning the
same topic using different methods at the same time will help
you to acquire more detailed ideas and widen your
understanding.

CIE 112 - Fundamentals of Surveying
Teachers’ Guide Module #4
Name:
_____________________________________________________
____________
Section: ____________ Schedule:
________________________________________
Class number:
_______
Date:
________________
This document is the property of PHINMA EDUCATION
2
1. Horizontal line departs
from a level surface
because of __?
2. How to eliminate the effect
of earth’s curvature and
refraction?
3. In long sights, the
horizontal line of sight
doesn’t remain straight but
it slightly bends
downwards having
concavity towards earth
due to __?
B.MAIN LESSON
1) Activity 2: Content Notes (13 mins)
Vertical Line – is a line that follows the local direction of gravity as indicated by a plumb
line.