Geodesy - Definition, Types, Uses and Applications

literature review speaks about the geodesy and its relation to the figure of the earth. The definition of geodesy and the imagining of the earth's shape evolution throughout history, it passed at many important developments. We will discuss that geodesy almost interferes with all Geo- and Space sciences, by clarifying some of its uses and applications.

1. Faculty of engineering - Shoubra
Benha University
Literature Review
in fulfillment of the requirements of
Department Surveying Engineering
Division
Academic Year Second Year Surveying
Course name Geodesy 1B
Course code SUR 223

Topic 3: “Geodesy Definition, Types, Uses and Applications.”

By:

Name Edu mail B. N
Ahmed Yasser Ahmed Mohamed Nassar [email protected] 210018

Approved by:

Examiners committee Signature
يكز دلاخ .د.أ
دعس ينم .د.م.أ
.د.م.أنيمأ رهام
ريغصلا يلع .د.أ

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Abstract
This literature review speaks about the geodesy and its relation to the figure of the earth.
The definition of geodesy and the imagining of the earth's shape evolution throughout
history, it passed at many important developments. We will discuss that geodesy almost
interferes with all Geo- and Space sciences, by clarifying some of its uses and
applications.

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Table of contents
Abstract ....................................................................................................................... 1
1. Introduction ........................................................................................................... 4
2. Literature Review ................................................................................................... 5
2.2. Brief History ..................................................................................................... 5
2.3. Types of Geodesy ............................................................................................. 6
2.3.1. Geometric Geodesy ....................................................................................... 6
2.3.2. Physical Geodesy .......................................................................................... 6
2.3.3. Satellite Geodesy .......................................................................................... 7
2.4. Uses and Applications of Geodesy .................................................................... 8
2.4.1. Uses of Geodesy ............................................................................................ 8
2.4.1.1. Boundary Determination ........................................................................ 8
2.4.1.2. Engineering Construction ........................................................................ 8
2.4.1.3. Topographic Mapping ............................................................................. 8
2.4.1.4. Traffic and Transportation ...................................................................... 9
2.4.1.5. Space Sciences ........................................................................................ 9
2.4.2. Applications of Geodesy ................................................................................ 9
2.4.2.1. Geodetic Datums .................................................................................... 9
2.4.2.2. Global Positioning Systems (GPS) .......................................................... 10
2.4.2.3. Geodetic Control Networks ................................................................... 11
2.4.2.4. Reference Frameworks ......................................................................... 11
2.4.2.5. International Terrestrial Reference System (ITRS) ................................. 11
2.4.2.6. Satellite Orbit Determination ................................................................ 12
2.4.2.7. Precise GPS Positioning in the Marine Environment .............................. 12
2.4.2.8. Determination of Precise Figure of Earth ............................................... 12
2.4.2.9. Geosciences and Environmental Applications ....................................... 12
3. Conclusions .......................................................................................................... 13
References ................................................................................................................. 14

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List of Figures







Figure I.D Description Page
1-1 Geoid Height computed from EGM2008 4
2-1 Geoid, Ellipsoid and Topography of Earth 5
2-2 Ellipsoidal Axis 6
2-3 Satellite measurement system 7
2-4 Satellite Laser Ranging Diagram 7
2-5 Boundary Determination 8
2-6 geodetic coordinate system 9
2-7 Geodetic Datums 9
2-8 geodetic surfaces and GPS satellites 10
2-9 Egyptian Geodetic Control Network 11
2-10 Plate Tactonics Movement Based on Space Geodesy 12

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1. Introduction
Geodesy is the science that locates objects on the Earth and relating them relative to
each other and determines the size, shape, and gravity of the earth. word GEODESY is
composed of two Greek words, GEO means Earth, and DESY means Dividing and
Measuring. The fundamentals of geodesy include reference systems, map projection
systems, geoid models, control systems, and Global Navigation networks. geodesy
science is dated back to the Sumerians of 5000 years ago, its subject and even its name
have been widely unknown. current explorations into the space and increasing
knowledge of science and interactions with the world surrounding us have made us
recognize the rising importance of geodesy.














Figure 1-1: Geoid Height computed from EGM2008

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2. Literature Review
2.1. Definition
Geodesy is defined as “a division of geomatics, surveying, and geosciences concerned
with the determination of the size, shape, orientation and gravity field of the Earth
(referred to as the geoid) and the exact positions of points on Earth's surface by
representing it in three-Dimensional space and changes of these properties with time .”
2.2. Brief History
In the sixth century B.C., Pythagoras assumed that the Earth was spherical in shape,
then the Greek Scientist Eratosthenes tried to estimate the size and circumference of the
sphere which Pythagoras assumed. Then Columbus and Magellan, through their
journeys around the world in the fifteenth and sixteenth centuries, supported the theory
of the spherical Earth. Newton came in 1687 with the theory of gravity and one of the
results of the theory was that the shape of the Earth is not completely sphere but flattened
at the poles. we need to define the shape and size of this surface so that we can determine
any location on the surface of the earth, the natural surface shape of the earth is not
regular so that we can express it easily, and it called Geoid.
2.3. Figure of Earth
Geoid (Figure 1-1) is defined as “the Earth's gravitational equipotential surface,
coinciding with the mean sea level.” geoid is a very complex surface, so it’s difficult to
mathematically define the geoid. The Ellipsoid, on the other hand, is a simple shape
generated by rotating an ellipse
?????? = ?????? + ??????
ℎ: Ellipsoidal Height
?????? : Orthometric Height
?????? : Geoidal Height (Undulation)
Figure 2-1: Geoid, Ellipsoid and Topography of Earth

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Ellipsoid (Figure 2-2) is a mathematically defined surface that approximates the
geoid, the true figure of the Earth.
Flattening: � =
�−�
�

1
st
eccentricity: �= √
�
2
−�
2
�
2

2
nd
eccentricity: �′= √
�
2
−�
2
�
2

2.3. Types of Geodesy

2.3.1. Geometric Geodesy
Geometric geodesy is mainly concerned with Geometric to find relations between the
specific locations of points on the surface of the Earth, and then study the size, shape,
and rotation of the Earth through Determination of some observations such as distances,
azimuths, angles... etc. by various methods such as triangulation, trilateration, electronic
surveys, etc. These observations define geometric relationships between points and their
position relative to a specific coordinate framework of the Earth. Choosing this
framework requires a large amount of information about the shape of the earth.
Coordinate systems are the most important products of geometrical geodesy
2.3.2. Physical Geodesy
Physical geodesy uses earth's gravity field measurements and characteristics along with
theories of this gravity field to determine the shape of the geoid and its relationship to
the geometric figure used to create the maps (ellipsoid) and in combination with arc
measurements, the earth's size. It is possible to determine geoid undulations and earth
flattening by having enough information about the Earth’s gravity field. These
operations are carried out using either gravitational observations, using astronomical
observations, or, more recently, using measurements on satellites.
Figure 2-2: Ellipsoidal Axis
1.2, the earth
d but it is not
So it is a mat
Ellipsoid, Sph
h is not in a
t a perfect elli
thematically d
ere, Geoid and
a spherical sh
ipsoid. The p
defined surfac
d actual topogra
hape. The E
polar radius o
ce of the earth
aphy of the ear
Earth’s shape
f earth is app
h.
rth

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2.3.3. Satellite Geodesy
Geometric and physical geodesy had been well developed until the middle of the 20th
century. Measurements of the Earth's figure and the Earth's gravity field were however
not satisfactory, since astro-geodetic surveys can only be performed on land rather than
across the sea. In areas such as the oceans, high mountains, and deserts, there were only
limited data from gravity surveys. Until the first artificial satellite launched in 1957,
satellite geodesy began to emerge, and geodesy developed into a completely new
technology. Not long after artificial satellites emerged, the Earth ellipsoid flattening
methods was used precisely by satellites. the constant growth of space technology, the
development of EDM devices, and the perfection of electronic data processing
equipment, satellites specifically equipped for geodetic purposes have been developed,
launched, observed and the data utilized. ANNA-1B was launched in 1962 as the first
real geodetic satellite, many observational systems such as geodetic cameras and
electronic ranging were developed and improved by ANNA. Project ANNA was also
useful in the development of Satellite Laser Ranging (SLR) (Figure 2-4) systems.









Figure 2-3: Satellite measurement system Figure 2-4: Satellite Laser Ranging Diagram

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2.4. Uses and Applications of Geodesy
Geodesy is a science dedicated to studying the earth's figure and external gravity. This
science used in surveying, positioning, navigation, topography and mappings, and the
study of a variety of terrestrial, air, marine, submarine and even extra-terrestrial gravity
phenomena…etc.
The science of geodesy has many uses in various fields, but we will mention only
some of them.

2.4.1. Uses of Geodesy

2.4.1.1. Boundary Determination
Geodesy play the primary role in determining and
documenting the coordinates of border markers
between states or administrative boundaries between
governorates . Boundary Determination depends on the
accurate positioning and GIS analysts.
2.4.1.2. Engineering Construction
When constructing any engineering projects (such as roads, bridges, dams, canals,
factories, etc.) it is necessary to determine their exact locations by defining the
coordinates of the various elements of the project and these coordinates are used in
planning the project as well as in following up the implementation throughout the
project stages.
2.4.1.3. Topographic Mapping
establish mapping triangle control network consisting of several geodetic stations and
to determine their horizontal and vertical coordinates.
Figure 2-5: Boundary Determination
1.2, the earth
d but it is not
So it is a mat
Ellipsoid, Sph
h is not in a
t a perfect elli
thematically d
ere, Geoid and
a spherical sh
ipsoid. The p
defined surfac
d actual topogra
hape. The E
polar radius o
ce of the earth

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2.4.1.4. Traffic and Transportation
A high efficiency and accuracy satellite navigation and positioning make a significant
decrease in traffic accidents and a vast improvement in transportation efficiency. The
navigation and positioning level of old means of travel is between several and ten
kilometers, whereas today's air and marine traffic is between several and ten meters.
2.4.1.5. Space Sciences
to launch, monitor, remotely control, spacecraft return need
a precise geodetic coordinate system(Figure 2-6), positions
of surface points in this system, and global gravity field
parameters of the surface points. A geodetic coordinate
system is used to describe a spacecraft’s movement relative
to the Earth, which is realized by a certain number of datum
points.
2.4.2. Applications of Geodesy

2.4.2.1. Geodetic Datums
there need to be corresponding reference points (geodetic datums) (Figure 2-7), which
surveying, and mapping results are referred to measure terrain, surface features, position
coordinates, heights, and gravity values at points on the Earth’s surface. Geodetic
datums mainly composed of Horizontal coordinate datums, vertical datums, sounding
datums, and gravity datums. Geodetic datums provide data for all types of surveying
and mapping works.



Figure 2-6: Geodetic Coordinate System
d but it is not
So it is a mat
Ellipsoid, Sph
h is not in a
t a perfect elli
thematically d
ere, Geoid and
a spherical sh
ipsoid. The p
defined surfac
d actual topogra
hape. The E
polar radius o
ce of the earth
aphy of the ear
Earth’s shape
f earth is app
h.
rth
Figure 2-7: Geodetic Datums

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2.4.2.2. Global Positioning Systems (GPS)
GPS Applications have varied considerably in the past years and Some of them are:
• Establishing geodetic networks and intensify the old networks.
• Monitor the displacement or landing of vital facilities, such as bridges, bridges, dams
and arches. And Monitor the movements of the Earth's crust.
• cadastral and topographic surveying works, and Produce accurate, detailed,
topographical and digital maps.
• Development of national geoid models in integration with the terrestrial leveling
method.
• Linking the different geodetic references of countries in cases of joint border
projects.
• Hydrographic surveying and development of sea and river maps.
• Fixing and documenting the locations of borders between countries.
• By integrating GPS and GIS, digital maps and portable data bases for cities with all
their details and services, is produced.








Figure 2-8: geodetic surfaces and GPS satellites

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2.4.2.3. Geodetic Control Networks
A geodetic control network (Figure 2-9) is a foundation on which precise and consistent
mapping, GIS, and surveying are based. Geodetic control points are traditionally
established as permanently placed, precisely
marked, located and documented, physical
monuments. A geodetic control network can be
established by using the GNSS (referred to as
International Terrestrial Reference Framework)
used as a 3-Dimensional geocentric reference
system for a country by developing satellite
surveying methods and their availability and
high degrees of accuracy.
2.4.2.4. Reference Frameworks
A geodetic reference framework forms the spatial base to create any Land-Information
System (LIS). this system Consisting of huge number of points whose locations have
been determined with respect to an accurate mathematical framework. it enables the
spatial referencing of all land data to specific positions on the surface of the Earth. A
geodetic reference framework provides an accurate and efficient means for positioning
data, uniform, effective language for interpreting and disseminating land information.
2.4.2.5. International Terrestrial Reference System (ITRS)
the International Terrestrial Reference System (ITRS) is a geocentric reference system.
the International Terrestrial Reference Frame (ITRF) is the reference frame derived
from (ITRS). Its origin is at the canter of whole earth's mass (land, oceans,
atmosphere...). ITRF unit of length is the meter. The ITRF is currently the primary
global spatial reference system but other regional reference frames have also been
developed.
Figure 2-9: Egyptian Geodetic Control Network
d but it is not
So it is a mat
Ellipsoid, Sph
h is not in a
t a perfect elli
thematically d
ere, Geoid and
a spherical sh
ipsoid. The p
defined surfac
d actual topogra
hape. The E
polar radius o
ce of the earth
aphy of the ear
Earth’s shape
f earth is app
h.
rth

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2.4.2.6. Satellite Orbit Determination
2.4.2.7. Precise GPS Positioning in the Marine Environment
2.4.2.8. Determination of Precise Figure of Earth
Geometrical Geodesy seeks to determine the precise size and shape of the earth and to
locate positions accurately on the earth's surface by geometrical and astronomical
measurements.
2.4.2.9. Geosciences and Environmental Applications
modern geodesy offers accurate geodetic information for the study of plate movement
and crustal deformation and new methods to develop accurate kinematic models of
recent plate movement (Figure 2-10) and crustal deformation. Very long baseline
interferometry (VLBI), SLR, and GPS can measure the precise and relative velocity of
plates with an approximate speed of 1 mm/year. geodesy determines crustal movements
with incredible space-time resolution, and then the stress-strain model inside the plates
can be established to test the validity of the rigid plate hypothesis, to deduce the
deformation inside the plates, and to provide the explanation of the tectonic processes.
Some geology and structures cannot be explained currently by plate tectonics, and
Geodesy is expected to make a new role here.




Figure 2-10: Plate Tactonics Movement Based on Space Geodesy

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3. Conclusions
At the end we discussed a brief introduction to geodesy. geodesy concept
summarized in the science of studying the shape, size, and rotation of the earth.
Geodesy is one of the oldest sciences on earth, from the Sumerian civilization to the
present day; it passed through radical developments, Geodesy stayed extremely
important in all fields of life, so it entered various branches of engineering such as
civil, surveying, and architectural planning, geosciences, space sciences, gravity
field...etc.

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References

Shaker, Ahmed. Geodesy. Surveying Department - Shoubra Faculty of Engineering,

Basic Geodesy. National Oceanic and Atmospheric Administration, 1977.

Dawod, Gomaa. Principles of Geodetic Surveys And GPS. 1st ed., 2012.

Lu, Zhiping et al. Geodesy: Introduction to Geodetic Datum And Geodetic Systems. 1st
ed., Springer-Verlag Berlin Heidelberg.

Seeber, Günter. Satellite Geodesy. 2nd ed., Walter De Gruyter, 2003.

Smith, James R. Introduction to Geodesy. Wiley, 1997.

Procedures and Standards for A Multipurpose Cadastre: The Geodetic Reference
Framework. National Academy Press, 1983.

"The International Terrestrial Reference System (ITRS) | GEOG 862: GPS And GNSS
For Geospatial Professionals". E-Education.Psu.Edu, 2020.