Why does my sat nav say I’m going slower than my speedometer?
Katie F asked:
My car’s speedometer says I’m going faster than my sat nav says I’m going.
My car’s speedometer says I’m going faster than my sat nav says I’m going.
Which one is likely to be the more accurate?
My petrol gauge is about a quarter of a tank out, so I’m not sure any of my car’s dials can be trusted!
PDA insurance
your car’s speedometer is most likely more correct. GPS’s just estimate your speed based on how much distance your covering in a certain amount of time. there will always be some delay in speed changes because the GPS needs time to calculate. your speedometer will always be more acurate than your GPS.
Sat Nav is probably more accurate. Run a time and distance check on your speedometer by using mile markers on the interstate. Run 10 miles at a constant 60 MPH, or as close to constant as you can. Check that it takes 10 minutes and that the odometer registers 10 miles. Just divide the actual time by 10 minutes and the odometer distance by 10 miles to find the % error.
Satellite is more accurate.