Lecture 2

GE 161 – Geomet Geometric ric Geodesy Geodesy

Introduction to Geodesy: General Concepts

Definitions, Definitions, Branches, Branches, Objectives, Objectives, Professions Professions and and Organizations, Organizations, History History and and Development Development Lecture No. 2 Department of Geodetic Engineering University of the Philippines

a.s. caparas/06

Geodesy... Geodesy... the the oldest oldest among among the the earth earth science science • dating dating back to the the Sumarians Sumarians 5000 years 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”. Lecture 2

GE 161 – 161 – Geometric Geodesy

General Concepts: Definitions, Branches, Branches, Objectives, Professions and Organizatio Organizations, ns, History and Development:

Definitions Definitions of of Geodesy Geodesy • Geodesy came from the Greek words “geo “g eo”” ad “d “des esa” a” me mean ans… s….. “ea “eart rth” h” an and d “ 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” Lecture 2



Definitions Definitions of of Geodesy Geodesy • The classical definition of geodesy is… “the science of measuring and portraying the Earth’s surfac sur face” e” (F. R. R. Helme Helmert, rt, 1880 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 -(Va nicek & Krakiwsky, Krakiwsky, 1986 1986)) Lecture 2



Concepts Concepts of of Geodesy 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 rotati on and and crustal crustal deform deformation ation Lecture 2



Geodesy Geodesy and and the the other other earth earth sciences sciences

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Branches Branches of of Geodesy Geodesy GEOMETRIC GEODESY

PHYSICAL GEODESY

GEODETIC ASTRONOMY

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SATELLITE GEODESY



Practice Practice and and Profession Profession of of Geodesy Geodesy • Universities and Government Institutions 

STUDY AND RESEARCH

• Private Institutions/Prac Institutions/Practitioners titioners 

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APPLICATIONS



In In the the Philippines… Philippines… • Universi University ty of the Philippin Philippines es - Train Training ing Center for Applied Geodesy and Photogramm Photo grammetry etry (UP TCAG TCAGP) P) • Coast and Geodetic Survey Department (CGSD)) – Natio (CGSD National nal Mapping Mapping and Resourc Resource e Information Authority (NAMRIA)

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The The Professionals… Professionals… 1. Theoreti Theoretical cal geodes geodesist ist – Ph. D. or or Master’s in Geodesy, Mathematics or Geophysics 2. Applied Applied Geodesist Geodesist – Geod Geodetic etic/Geom /Geomatics atics Engineers 3. Survey Technician Lecture 2



The The Geodetic Geodetic Community Community IUGG

IAG

IGB Lecture 2

IERS GE 161 – 161 – Geometric Geodesy

IGS General Concepts: Definitions, Branches, Branches, Objectives, Professions and Organizatio Organizations, ns, History and Development:

The Sto ry of Earth ’s Size Sh ape… The Story Story Story of Earth’s Earth’s Earth’s Size and and and Shape… Shape… Shape … the the mother mother of of Geometric Geometric Geodesy Geodesy It was the shape that comes first…. • began with the Greeks (Homer) theorizing the earth as a “flat disc” • then Anaxima Anaximander nder a.k.a a.k.a.. Anaximenes Anaximen es thought the earth 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 philosoph philosopher er by the name of Pythagoras believed the earth was not flat but round. Lecture 2



The Sto ry of Earth ’s Size Sh ape… The Story Story Story of Earth’s Earth’s Earth’s Size and and and Shape… Shape… Shape … the the mother mother of of Geometric Geometric Geodesy Geodesy • 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. Lecture 2



The Sto ry of Earth ’s Size Sh ape… The Story Story Story of Earth’s Earth’s Earth’s Size and and and Shape… Shape… Shape … the the mother mother of of Geometric Geometric Geodesy Geodesy 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 Lecture 2



The Sto ry of Earth ’s Size Sh ape… The Story Story Story of Earth’s Earth’s Earth’s Size and and and Shape… Shape… Shape … the the mother mother of of Geometric Geometric Geodesy Geodesy • 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. Lecture 2



The Sto ry of Earth ’s Size Sh ape… The Story Story Story of Earth’s Earth’s Earth’s Size and and and Shape… Shape… Shape … the the mother mother of of Geometric Geometric Geodesy Geodesy 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 Lecture 2



The Sto ry of Earth ’s Size Sh ape… The Story Story Story of Earth’s Earth’s Earth’s Size and and and Shape… Shape… Shape … the the mother mother of of Geometric Geometric Geodesy Geodesy •

•

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 Lecture 2



References: References: • National Oceanic and Atmospheric Administration (1985), Geodesy for the Layman Fifth Edition (online), US Department of Commerce. • Roc Rockvi kville, lle, Md Md (19 (1973) 73),, Basic Geodesy (online), Geodesy (online), US Department of Defense, Defense Mapping School, reprint by NOAA US Department of Commerce (1977)\ • Van Vanicek icek,, Ptr Ptr (20 (2001) 01),, An Online Tutorial on Geodesy (online Geodesy (online), ), Academ AcademicPress icPress 2001, University of New Brunswick, Canada. Lecture 2



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