Fragment z tego artykułu.

The combination of these two relativitic effects means that the clocks on-board each satellite should tick faster than identical clocks on the ground by about 38 microseconds per day (45-7=38)! This sounds small, but the high-precision required of the GPS system requires nanosecond accuracy, and 38 microseconds is 38,000 nanoseconds. If these effects were not properly taken into account, a navigational fix based on the GPS constellation would be false after only 2 minutes, and errors in global positions would continue to accumulate at a rate of about 10 kilometers each day! The whole system would be utterly worthless for navigation in a very short time.

Przepraszam, że nie po polsku. Efekty relatywistyczne trzeba uwzględniać. Chodzi o kumulację błędów, a nie statyczne rozważania dla wybranego momentu.

Wystarczy w gugla wpisać "relativity theory in gps" i dostanie się milion artykułów na ten temat. Nie ze stron typu "alternatywna fizyka" - dziwnie to brzmi.