Optics · Fig. 1 · interactive

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Fig. 1 — Ray paths through a lensdrag
Image b
Magnification
Lens equation
1/f = 1/a + 1/b
Fig. — 4 satellites, one instant in time
Featured · Navigation

How satellites know where you are

Four signals, one instant in time and a pinch of relativity. We take GPS apart — orbit by orbit, microsecond by microsecond.

Read the article 18 min · verified 06.2026
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