State PCS
The science of precisely measuring and understanding the Earth's shape, orientation in space and gravity field is called:
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Answer: Option C — Geodesy
Detailed Solution
Geodesy is the science of accurately measuring and understanding three fundamental properties of the Earth: its geometric shape, its orientation in space and its gravity field, and how these change over time.
Meaning of the word:
"Geodesy" comes from the Greek words "ge" (Earth) and "daiein" (to divide), originally meaning the division of the Earth into areas.
What geodesy studies:
- The exact shape and size of the Earth, which is not a perfect sphere.
- The geoid, an imaginary surface that matches mean sea level extended under the continents, shaped by the Earth's gravity.
- Precise positions of points on the Earth's surface.
- Changes in the Earth's rotation and the position of its axis.
- Variations in gravity from place to place.
- Movements of the Earth's surface, such as plate motion, land subsidence and the rise of sea level.
Tools and techniques:
- Global Navigation Satellite Systems (GNSS), such as GPS (USA), GLONASS (Russia), Galileo (Europe), BeiDou (China) and India's NavIC.
- Satellite laser ranging and very long baseline interferometry (VLBI), which uses radio signals from distant quasars.
- Gravity-measuring satellites, such as GRACE and GOCE.
- Satellite altimetry, which measures the height of the sea surface from space.
Uses of geodesy:
- Making accurate maps and setting national reference systems.
- Navigation, including GPS in phones and vehicles.
- Monitoring earthquakes, volcanoes, glaciers and sea-level rise.
- Engineering projects such as dams, bridges and railways.
Geodesy in India:
- The Great Trigonometrical Survey (GTS), started in 1802 by William Lambton and continued by George Everest, measured the Indian subcontinent with remarkable accuracy.
- The Survey of India, founded in 1767, is the national mapping agency and carries out geodetic work today.
- The height of Mount Everest was first calculated during this survey, and the mountain was named after George Everest.
Why not the other options?
- ✗Geology is the study of the Earth's rocks, minerals, structure and history.
- ✗Geomorphology is the study of landforms and the processes that shape them.
- ✗Cartography is the science and art of making maps.
Quick tip
Remember: Geodesy = measuring Earth's shape, orientation and gravity field; India's Great Trigonometrical Survey began in 1802.
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Earth: Structure, Rocks & Landforms — Preparation
This question tests your understanding of Earth: Structure, Rocks & Landforms, a key topic in the General Knowledge section. The detailed solution above uses a step-by-step approach to show the reasoning, and where available, a shortcut that helps you solve similar questions in under 90 seconds during the actual exam.
This topic covers the interior of the Earth (crust, mantle and core), types of rocks, plate tectonics and continental drift, earthquakes and volcanoes, and the landforms created by rivers, glaciers, wind and waves. Questions frequently ask about the layers of the Earth and their discontinuities, the three types of rocks (igneous, sedimentary and metamorphic), the Pacific 'Ring of Fire', and which agent forms which landform, such as river meanders and oxbow lakes or glacial cirques and moraines. Alfred Wegener proposed the continental drift theory in 1912. Practise the Earth's structure and landforms questions below, written in the style of the general awareness sections of exams such as SSC, banking, railways, CUET GAT, MAH CET and CLAT. Each question comes with a detailed explanation that adds related facts, so every question helps you revise more than one point.