Lecture 2

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a.s. caparas/06a.s. caparas/06

GE 161 – Geometric Geodesy

Lecture No. 2

Department of Geodetic EngineeringUniversity of the Philippines

Introduction to Geodesy: General ConceptsIntroduction to Geodesy: General Concepts

Definitions, Branches, Objectives,Professions and Organizations,

History and Development

Definitions, Branches, Objectives,Definitions, Branches, Objectives,Professions and Organizations,Professions and Organizations,

History and DevelopmentHistory and Development

Lecture 2Lecture 2 GE 161 GE 161 –– Geometric GeodesyGeometric GeodesyGeneral Concepts: Definitions, Branches, General Concepts: Definitions, Branches,

Objectives, Professions and Organizations, Objectives, Professions and Organizations, History and Development: History and Development:

Geodesy... the oldest among the earth scienceGeodesy... the oldest among the earth science

• dating back to the Sumarians 5000 years ago when man first became interested with his surroundings.

• it all started with the concern of what is “my house’s immediate vicinity”

• later it expanded to the distances of markets and exchange places

• and with the development means of transportation, man became interested in his “whole world”.

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Definitions of GeodesyDefinitions of Geodesy

• Geodesy came from the Greek words “geo” ad “desa” means…. “earth” and “ to divide”.

• Webster defines geodesy as..“that branch of applied mathematics which

determines by observation and measurement the exact positions points and the figure and areas of large portion of the earth’s surface, the size and shape of the earth, and the variations in the terrestrial gravity”



Definitions of GeodesyDefinitions of Geodesy

• The classical definition of geodesy is…“the science of measuring and portraying the Earth’s

surface” (F. R. Helmert, 1880)

• The contemporary definition of geodesy is…

“the discipline that deals with the measurement and representation of the Earth’s surface, including its gravity field, in a three-dimensional time varying space”

-(Vanicek & Krakiwsky, 1986)

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Concepts of GeodesyConcepts of Geodesy• All the definitions of geodesy will include three

general ideas or concepts:…. the size and shape of the earth…. the gravity field of the earth…. the positioning of points on the

surface of the earth• In its modern definition it also include

measurement and modeling of the geodynamic phenomena such as polar motion, Earth rotation and crustal deformation



Geodesy and the other earth sciencesGeodesy and the other earth sciences

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Branches of GeodesyBranches of Geodesy

GEODESYGEODESY

GEOMETRIC GEODESY

PHYSICAL GEODESY

SATELLITE GEODESY

GEODETIC ASTRONOMY



Practice and Profession of GeodesyPractice and Profession of Geodesy

• Universities and Government Institutions STUDY AND RESEARCH

• Private Institutions/Practitioners APPLICATIONS

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In the Philippines…In the Philippines…

• University of the Philippines - Training Center for Applied Geodesy and Photogrammetry (UP TCAGP)

• Coast and Geodetic Survey Department (CGSD) – National Mapping and Resource Information Authority (NAMRIA)



The Professionals…The Professionals…

1. Theoretical geodesist – Ph. D. or Master’s in Geodesy, Mathematics or Geophysics

2. Applied Geodesist – Geodetic/GeomaticsEngineers

3. Survey Technician

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The Geodetic CommunityThe Geodetic Community

IUGG

IGB

IAG

IERS IGS



The Story of Earth’s Size and Shape… the mother of Geometric Geodesy


It was the shape that comes first….• began with the Greeks (Homer)

theorizing the earth as a “flat disc”• then Anaximander a.k.a.

Anaximenes thought the earth as a rectangular object

• Next was the view of earth as sphere but exactly when the notion of a spherically shaped earth first came into existence is not known.

• However, recorded history reveals that as early as the sixth century B.C., a Greek philosopher by the name of Pythagoras believed the earth was not flat but round.

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• Three centuries later, Aristotle (384-322 B.C.) considered the idea of a round earth as he studied the movement of planets.

• From his observations, particularly those of lunar eclipses, he concluded that the earth was indeed spherical in shape.





after the shape, the size came in…..• the first approximation of the

earth’s circumference was proposed by Plato at 40,000 miles

• then Archimedes approximate it at 30,000 miles

• Meanwhile around 250 B.C., in Egypt, a Greek scholar and philosopher, Erathosthenes, set out for a more explicit measurement of the size of the earth

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• Eratosthenes developed a simple method for calculating the earth’s circumference.

• Using a knowledge of the sun’s position relative to the earth and some principles of geometry, he calculated the earth’s equatorial circumference to be 25,000 miles.





but the search for better figure that defines the shape of the earth continues….

• In the 17th century, the theory that earth is not a perfect sphere arises.

• However, these resulted to an intense controversy between the French and the English

• The English claimed that the earth must be flattened but the French defended their claim for an egg-shape earth

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• To settle the issue the French Academy of Sciences, in 1735, sent out an expedition to confirm the correctness of the claims.

• The measurements of the expedition in Peru conclusively proved the earth to be flattened.

But the story does not end there…• The pear-shaped earth was

introduced in view of the gravitational influence on the surface

• And lastly, the potato-shaped earth was introduced to consider the uneven distribution of masses on the surface of the earth



References:References:• National Oceanic and Atmospheric

Administration (1985), Geodesy for the Layman Fifth Edition (online), US Department of Commerce.

• Rockville, Md (1973), Basic Geodesy (online), US Department of Defense, Defense Mapping School, reprint by NOAA US Department of Commerce (1977)\

• Vanicek, Ptr (2001), An Online Tutorial on Geodesy (online), AcademicPress 2001, University of New Brunswick, Canada.

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Lecture 2