The Reason Your GPS Is Always Slightly Wrong — and the Fix

3. The Relativity Factor - Einstein's Impact on Your Morning Commute

Albert Einstein's theories of special and general relativity play a crucial and often overlooked role in GPS accuracy, demonstrating how fundamental physics directly impacts everyday technology. GPS satellites orbit Earth at approximately 8,700 miles per hour, causing their onboard atomic clocks to run slower than identical clocks on Earth's surface by about 7 microseconds per day due to special relativity. Simultaneously, the weaker gravitational field at the satellites' altitude causes their clocks to run faster than Earth-based clocks by about 45 microseconds per day according to general relativity. The net effect is that satellite clocks gain approximately 38 microseconds per day relative to Earth-based time standards. Since GPS positioning depends on extremely precise timing measurements—with each microsecond of error translating to roughly 1,000 feet of positioning error—these relativistic effects would render the system completely useless within hours if left uncorrected. GPS satellites compensate for these effects by running their clocks at a slightly different rate (10.22999999543 MHz instead of exactly 10.23 MHz) so that they appear to keep perfect time when observed from Earth. However, relativistic effects also vary with satellite altitude and velocity, and the mathematical models used to compensate for these effects introduce small residual errors that contribute to the overall uncertainty in GPS positioning calculations.