Why a Trip Distance Might Seem Off
Why a Trip Distance Might Seem Off
If a trip's distance looks too high or too low compared to what you expected, here are the common reasons.
How distance is calculated
SmartMiles records GPS points as you drive, then matches that path to real roads using a process called map matching.
The distance is measured along the matched road route — not a straight line between start and end.
This means the distance reflects the actual roads you drove on, including turns, detours, and highway ramps.
Distance seems too high
You took a longer route. SmartMiles measures the route you actually drove, which may be longer than the most direct
path. If you took a detour, went through a drive-through, or circled looking for parking, those extra miles are
included.
GPS drift. If GPS accuracy was poor (tall buildings, tunnels, dense trees), the recorded path may zig-zag slightly,
adding small amounts of extra distance. SmartMiles minimizes this with road snapping, but it cannot fully correct very
noisy GPS data.
Distance seems too low
GPS signal was lost. If your phone lost GPS signal for part of the trip (tunnel, parking garage, phone restart), that
portion of the route may be missing or estimated.
The trip was split. If you made a long stop during a trip (e.g., got out of the car for a while), SmartMiles may have
recorded it as two separate shorter trips instead of one long one.
Distance on a manual trip
For manual trips, SmartMiles calculates the driving distance using the most direct driving route between your start and
end locations. This may differ from the route you actually took.
Can I edit the distance?
No. Trip distances are calculated from GPS data (or routing data for manual trips) and cannot be manually overridden.
This ensures your mileage log is accurate and based on actual driving data, which is what the IRS expects.
What to do
If a trip distance seems significantly wrong:
- Check the trip's route map — it shows the recorded path, which can help you understand where the discrepancy came
from.
- If the trip was split, you may want to delete the fragments and add a manual trip for the full route.
- If trips consistently show wrong distances, check that your location permissions are correctly set — poor GPS data
is the most common cause.
