The Earth is not a perfect sphere, but is instead more like a slightly squashed sphere called an ellipsoid. Because of this, GPS receivers must use a correction model (called a geoid) to calculate true elevation above sea level. UNAVCO has prepared this explanation for both teachers and students to learn more about accuracy, scientific models, and how GPS receivers work.
Subject: Geoscience:Geology:Geophysics:Geodesy, Geography:Geospatial Resource Type: Scientific Resources:Overview/Reference Work
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