Transcript Surveying I. – Lecture 1

Surveying I.
Lecture 1.
Sz. Rózsa: Surveying I. – Lecture 1
Outline
Introduction
Historical Surveying
Surveying - Science and Profession
Methods of height determination
Levelling
The surveyors’ level
Sz. Rózsa: Surveying I. – Lecture 1
Introduction
Lecturers:
Lectures
Dr. Szabolcs Rózsa
Department of Geodesy and Surveying,
K. building groundfloor 16.
Practicals
Dr. Lóránt Földváry
Department of Geodesy and Surveying,
K. building groundfloor 16.
Mr. Albert Kiss
Department of Geodesy and Surveying
K. building groundfloor 16.
Sz. Rózsa: Surveying I. – Lecture 1
Introduction
Course details:
• First part of a two-semester-course
• 4 hours/week (equally divided between lectures and
practicals)
Communication:
• Activities involve lectures, practicals, tutorials and a field
practice
• Lectures - provide the theoretical background of the topics
• Practicals - practical sessions, in which You’ll carry out
measurements and process them.
• Tutorials - if there’s a need for additional guidance in the
preparation for assessments. Please note that You have to
arrange an appointment in due time.
• Field practice - a 9-day-long intensive course after the
course Surveying II.
Sz. Rózsa: Surveying I. – Lecture 1
Introduction
Attendance:
• Please attend all scheduled lectures, seminars and
practicals
• Please note: attendance falling below 70% may lead to
failing the course irrespective of the academic performance.
Sz. Rózsa: Surveying I. – Lecture 1
Introduction
Classroom tests:
• Altogether 4 classroom assessments:
• Practicals 1-4 (10 points)
• Using a theodolite – must pass
• Practicals 10-11 (10 points)
• Theory (involving the topics of the lectures) – 80
points
Course Evaluation:
Excellent
good
satisfactory
pass
fail
(5)
(4)
(3)
(2)
(1)
87-99
75-87
62-74
50-61
0-49
You’re required to achieve a minimum of 50% in each classrom
test to pass the course.
Sz. Rózsa: Surveying I. – Lecture 1
Introduction
Learning resources:
• Some of the lecture notes are available for download on
the website of the department:
http://www.geod.bme.hu/index_e.html
• However You shall write own notes during the lectures,
too.
• You’ll be suplied with computational sheets, field notes
etc. during the course.
• Textbook:
A. Bannister - S. Raymond - R. Baker: Surveying (Seventh
Edition, Prentice Hall, 1998)
Cca. 16000 HUF
Sz. Rózsa: Surveying I. – Lecture 1
Website
Lecture notes can be downloaded from:
http://www.geod.bme.hu/index_e.html
Sz. Rózsa: Surveying I. – Lecture 1
Website
Sz. Rózsa: Surveying I. – Lecture 1
Outline
Introduction
Historical Surveying
Surveying - Science and Profession
Methods of height determination
Levelling
The surveyors’ level
Sz. Rózsa: Surveying I. – Lecture 1
Historical Surveying
What is Surveying?
The art of making measurements of the relative positions of
natural and man-made features on the Earth’s surface, and
the presentation of this information either graphically or
numerically.
Since when?
The first surveying works date back to the antiquity, the
Greek provided the first account of surveying techniques.
Euclid founded the theoretical background for surveying by
the development of his geometry.
Sz. Rózsa: Surveying I. – Lecture 1
Historical Surveying
Eratosthenes
(ca. 250 BC)
„Spherical Earth”
Sz. Rózsa: Surveying I. – Lecture 1
Historical Surveying
Sz. Rózsa: Surveying I. – Lecture 1
Outline
Introduction
Historical Surveying
Surveying - Science and Profession
Methods of height determination
Levelling
The surveyors’ level
Sz. Rózsa: Surveying I. – Lecture 1
Surveying - Science and Profession
Surveying vs. Geodesy
• in most languages there are no distinctions between
the terms
• in English (according to Vanicek - Krakiwsky):
• Surveying: the practice of positioning
• Geodesy: the theoretical foundation of surveying
Geodesy is the scientific background of Surveying as a
profession.
Sz. Rózsa: Surveying I. – Lecture 1
Surveying - Science and Profession
Surveying:
The art of making measurements of the relative positions of
natural and man-made features on the Earth’s surface, and
the presentation of this information either graphically or
numerically.
Geodesy:
Geodesy is the discipline that deals with the measurements
and representation of the Earth, including its gravity field,
in a three-dimensional time varying space.
Geodesy focus on the Earth and neglect any man-made
features on it (e.g. buildings, public utilities, etc.), while
surveying use the results of geodesy for positioning and
mapping of these features.
Sz. Rózsa: Surveying I. – Lecture 1
Basic principles of Surveying
Recall the definition of Surveying:
The positioning is usually
The art of making measurements of the relative
positions of natural and man-made features on separated
the Earth’sinto horizontal (2D)
and vertical
surface, and the presentation of this information
either (1D) positioning.
graphically or numerically.
Nowadays 3D positioning can
be achieved using satellite
techniques, too.
How to achieve this?
Let’s determine the position (XP, YP) of point P!
Absolute vs Relative positioning
XP
Y
dBP
P
dAP
B
(XB,YB)
YP
Control points
(known coords;
marked on the field)
A
(XA,YA)
l AB
X
Sz. Rózsa: Surveying I. – Lecture 1
Basic principles of Surveying
Let’s determine the position of a third, unknown point (C).
We have two unknowns: XP, YP
b
We need two measurements:
a
• two distances
Y
• one distance and an angle
P
• two angles
dBP
dAP
dAP
b
B
a
(XB,YB)
a
A
(XA,YA)
X
Sz. Rózsa: Surveying I. – Lecture 1
Classification of Surveying
Plane Surveying
According to the space involved:
• relatively small areas
• surface of earth can supposed to be
flat
Note: The two radii can supposed to be
parallel, when the l(A,B) is small.
• measurements plotted represent a
horizontal projection of the actual field
measurements
Sz. Rózsa: Surveying I. – Lecture 1
Geodetic Surveying
Classification of Surveying
Don’t forget! Size does matter!
• large areas
• surface of the Earth can not supposed to be flat
• the curvature of the Earth is taken into account
Mostly used for establishing control networks, determining the size and shape
of the Earth and determining the gravity field of the Earth.
Sz. Rózsa: Surveying I. – Lecture 1
How to create a countrywide coordinate system?
In order to use the relative positioning, a proper number of control points
are needed. These points:
• are coordinated points;
• are marked.
Sz. Rózsa: Surveying I. – Lecture 1
Control Networks
Why is it necessary to have a common countrywide coordinate
system?
Many engineering tasks cover a large area (highways, bridges,
tunnels, channels, land registry, etc.), where the common coordinate
system (reference system) should be available.
The Control Network provide us with control points given in the
same refence system (coordinate system).
Thus measuring the relative positions of unknown points using these
control points, the coordinates of the new points can be computed
in the same reference system.
Sz. Rózsa: Surveying I. – Lecture 1
The role of Surveying in Civil Engineering Practice
Surveyors are needed:
• to maintain the geometric order during the
construction process
• to provide fundamental data for the design and
planning process
• to provide quantity control during the construction
process (for example: earthwork quantities)
• to monitor the structure after the construction
(subsidence, deformations,
etc.)
What is
this?
Wrong
geometry
theappropriate
structure is geometry,
not functional!
Laying
them in–the
outstanding structures can be created!
Sz. Rózsa: Surveying I. – Lecture 1
The role of Surveying in Civil Engineering Practice
Surveying activities during the construction process
Before Construction
Under construction
After construction
Planning and
data collection
Setting out on each
phase
of construction
Final (as-built)
plan or map
on the construction
Observations
in the field
Field checks of
construction
Presenting
documentation
to the client
Processing the
observations
(office)
Providing data
and services to
the client
Deformation
Monitoring/
Load Tests
Drawing maps,
plans or providing
numerical data
Presenting
documentation
to the client
Sz. Rózsa: Surveying I. – Lecture 1
Outline
Introduction
Historical Surveying
Surveying - Science and Profession
Methods of height determination
Levelling
The surveyors’ level
Sz. Rózsa: Surveying I. – Lecture 1
Methods of height determination
Question 1:
What does the height (elevation) of a point mean?
Question 2:
What does it mean, when point B is at a higher elevation
than point A?
Answer 1:
The height of a point represents its energy level above a
reference level.
Answer 2:
For example water flows from point B to point A.
Sz. Rózsa: Surveying I. – Lecture 1
Methods of height determination
Definition of height systems:
• The potential energy of a point should be represented by the height of
a point. Hence water should flow from the higher elevation towards the
lower elevation.
• Should have metric unit.
What should be the reference of height determination? What
is the 0 level?
• Since the height systems should represent the potential energy
level, we need a reference surface, which is an equipotential surface
of Earth’s gravity field.
• The surface of calm water forms an equipotential surface
• Mean Sea Level – Kronstadt (Baltic Sea) is used in Hungary
(formerly Triest, Adriatic Sea).
Sz. Rózsa: Surveying I. – Lecture 1
Methods of height determination
Equipotential surfaces
B
A
HB
HA
MSL
equipotential surface
g
Gravity vector is always perpendicular to the equipotential surface.
Equipotential surface
(=)
horizontal surface
Gravity vector
(=)
vertical direction
Sz. Rózsa: Surveying I. – Lecture 1
Methods of height determination
1D position determination - determining the height
We can not determine absolute heights above the reference level
Relative height determination - determining the height
differences
Levelling benchmarks are needed - control points for which the
elevation is known.
B
H BA  H B  H A
A
HB
HA
Reference level
Sz. Rózsa: Surveying I. – Lecture 1
Methods of height determination
How can we determine the height difference?
Two solutions:
• setting a horizontal plane, and measuring the offset from this plane
• measuring the slope and slope distance between the points
Levelling
Trigonometrical height determinationB
l AB
H BA  H B  H A
a
A
HB
HA
Reference level
Sz. Rózsa: Surveying I. – Lecture 1
Outline
Introduction
Historical Surveying
Surveying - Science and Profession
Methods of height determination
Levelling
The surveyors’ level
Sz. Rózsa: Surveying I. – Lecture 1
The principle of levelling
Line of sight
dA
(lA)
dB
lA
A
lB
(lB)
HAB
B
HAB=lA-lB=(lA)-dA-(lB)+dB
When dA=dB (spherical approximation, equal distance to A and B)
HAB=(lA)-(lB)
Sz. Rózsa: Surveying I. – Lecture 2
1
Levelling
Over short distances the horizontal line and level line coincide.
For a distance of 100m the effect of the curvature is less than 1 mm.
The levelling device (called level) must be set up so, that the line of sight is
perpendicular to the gravity vector (plumb line). -> the line of sight is horizontal.
Horizontal
line of sight
Graduatedstaff
Level
Graduatedstaff
Difference
in height
Sz. Rózsa: Surveying I. – Lecture 1
Levelling
Sz. Rózsa: Surveying I. – Lecture 1
Outline
Introduction
Historical Surveying
Surveying - Science and Profession
Methods of height determination
Levelling
The surveyors’ level
Sz. Rózsa: Surveying I. – Lecture 1
The Surveyor’s level
Tilting level
Bubble tube
Diaphragm
Tilting screw
Tilting axis
Circular bubble
Levelling head
Clamping screw - to fix the telescope in one vertical plane
Tangent screw (slow motion screw) - to finely rotate the telescope
along a vertical axis
Sz. Rózsa: Surveying I. – Lecture 1
Elements of Surveyor’s level
How to set the line of sight to be exactly horizontal?
More general: how to set anything to be exactly horizontal?
The bubble tube
Sz. Rózsa: Surveying I. – Lecture 1
The bubble tube
The radius determines the sensitivity of the bubble tube:
a
a
R1
R2
R1 greater than R2
Sensitivity: how much the bubble moves due to a given
amount of inclination. The more the bubble moves, the more
sensitive the bubble tube is.
Sz. Rózsa: Surveying I. – Lecture 1
The bubble tube
The determination of sensitivity:
a
a
R1
R1
l2  l1
 a radians
L
a
l1
L
l2
a "  a radians 206264.8
L
Sz. Rózsa: Surveying I. – Lecture 1