GPS – Bartosz Ciechanowski
ciechanow.ski/gps
What Jamie wrote
Even if you know how the GPS system works this article is worth spending some time on. It is an incredibly well done explainer of the location techniques used by GPS, and the interactive diagrams do a great job of illustrating the concepts right in front of your eyes. This will give you a detailed understanding of how these little devices can tell you where you are, anywhere in the world.