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chapter 1.2

PART A: SHORT-ANSWER EXAM QUESTIONS WITH ANSWERS These are classic scoring questions . Memorize the keywords and you’re safe. 1. Define geodesy. Answer: Geodesy is the science of measuring and representing the Earth’s shape, size, gravity field, and temporal variations , and establishing accurate coordinate systems. 2. What did Eratosthenes contribute to geodesy? Answer: He measured the Earth’s circumference using shadow angles and distance , proving the Earth is spherical with remarkable accuracy. 3. Differentiate between ellipsoid and geoid. Answer: Ellipsoid: Mathematical, smooth surface used for calculations Geoid: Irregular gravity-based surface approximating mean sea level 4. What is a datum? Answer: A datum is a reference framework defining the origin, orientation, and scale for coordinate systems. 5. Why is Everest 1830 unsuitable for GNSS? Answer: It is: Local and outdated Not Earth-centered Causes distortions when used with satellite-based systems 6. What is ITRF? Answer: ...
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chapter1.1

  A. EXAM NOTES Geodesy: From Eratosthenes to the Digital Earth 1. Definition of Geodesy Geodesy is the science of measuring and representing the shape, size, orientation, gravity field, and temporal variation of the Earth . Core objectives: Determine Earth’s geometry Establish coordinate systems and datums Monitor Earth’s deformation and gravity changes 2. Historical Development a) Ancient Geodesy Eratosthenes (≈240 BCE) Used shadow angles and distance between Syene and Alexandria Estimated Earth’s circumference with ~1% error Proved Earth is spherical Key idea: Geometric reasoning + observation b) Classical to Medieval Period Greeks: spherical Earth models Romans: cadastral surveying, roads, aqueducts Islamic scholars: refined Earth measurements and astronomy c) 17th–19th Century Newton: Earth is an oblate spheroid Arc measurements confirmed polar flattening Development of triangulation networks Introduction of precision ...
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Chapter1

 Geodesy. The science that exists because humans refused to accept “the Earth looks flat enough” and instead chose math, shadows, and later, satellites. Here’s the clean arc from ancient flexes to modern overkill. 1. Motivation: Why Geodesy Exists Humans needed to: Measure land so neighbors stop fighting over fields. Navigate without accidentally discovering a new continent. Build big things that do not collapse due to “close enough” thinking. Understand Earth as a physical object, not vibes. Flat-Earth energy died early because reality kept interrupting. 2. Historical Evolution a) Eratosthenes (≈240 BCE): The Original Gigachad Measured Earth’s circumference using two sticks, shadows, and logic . Assumed Earth is spherical. Correct. Result was off by ~1%. Ancient accuracy that humiliates some modern surveys. Method: Noon sun angle difference between Syene and Alexandria Used distance + angle → circumference No satellites. No calculator...
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Geodesy

 Geodesy is the science of measuring and understanding Earth. Yes, the entire planet. No pressure. In slightly more serious terms, geodesy deals with determining the shape, size, orientation, and gravity field of the Earth , plus how these things change over time. Because Earth refuses to be a perfect sphere and insists on being a lumpy, spinning, slightly chaotic object. At its core, geodesy answers questions like: Where exactly is this point on Earth? How far is it from that other point? How is Earth’s surface moving, sinking, or rising? How does gravity vary from place to place? Geodesy is the backbone of surveying, mapping, GPS, satellite navigation, civil engineering, space science, and tectonic studies . Every time your phone knows where you are, thank a geodesist who lost sleep over reference ellipsoids. Main branches of geodesy Geometric geodesy : Focuses on Earth’s shape and dimensions using measurements like distances, angles, and coordinates. Physical geodesy : Studies E...
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