Understanding Earth's Shape: Geoid vs. WGS84 Ellipsoid

Ever wonder why the Earth's true shape is a "wonky" gravity model, but your GPS uses a smooth mathematical ellipsoid? In this lesson, we break down the fundamental geodetic models used in offshore and hydrographic surveying. We explore how irregular global features and gravitational variances are converted into standardized spatial coordinates, and why understanding the difference between physical gravity frameworks (Geoid) and mathematical reference models (Ellipsoid/Spheroid) is essential for high-precision measurement. 00:00 – The true shape of Earth 01:20 – Requirements for measurement 03:37 – Defining the Geoid 04:19 – Factors changing Earth's mass 05:27 – The reference spheroid 06:01 – The oblate spheroid 06:24 – WGS84 parameters 07:23 – Geoid vs. Spheroid 08:25 – Earth Gravity Models (EGM) 09:38 – International Terrestrial Reference Frame (ITRF) 10:12 – Deflection of the vertical WHAT YOU WILL LEARN: Spherical vs. Planar: Why large-scale geographic distances require spherical geometry rather than simple planar calculations. The Geoid: Defined as an irregular, gravity-based mathematical shape representing global mean sea level. The Spheroid/Ellipsoid: Why we use smooth, regular mathematical models like WGS84 for global positioning and height measurements. Deflection of the Verticals: Why gravitational verticals and ellipsoidal normals don't always align, creating measurement errors in the field. Gravitational Updates: How global mass redistribution—from melting ice caps to mining—forces frequent updates to models like EGM 2008. Understanding these concepts is critical for any surveyor or navigator. Subscribe to Offshore Surveys for more professional-grade technical content on geodesy and navigation physics. #Geodesy #Geoid #Spheroid #Ellipsoid #Hydrography #OffshoreSurveying #GPSAccuracy #CoordinateSystems #WGS84 #Datums #NavigationScience #GIS 🍵Buy me a coffee🍵 https://buymeacoffee.com/jaom Join this channel to get access to exclusive offshore survey videos:    / @offshoresurveys