GpxFix Blog

Why Your Activity Distance Is Wrong And How to Correct It

By Roy Lachica on March 13, 2026. Last updated March 13, 2026.

Have you ever finished a run, ride, or hike and noticed that the recorded distance seems wrong? Maybe your watch says you ran 10.8 km on a known 10 km route, or perhaps it shows 9.6 km. GPS tracking is incredibly useful, but it is not perfect. Small errors during recording can accumulate and cause your total distance to be inaccurate.

In this article we’ll explain the most common reasons activity distance becomes incorrect, including GPS drift, bad sampling, pauses, and sensor errors — and how you can correct these issues in your activity data.

How Activity Distance Is Calculated

Most sports watches, bike computers, and mobile fitness apps calculate distance using GPS track points. Each recorded point contains latitude and longitude coordinates. The device calculates the distance between each consecutive point and sums them together to produce the total activity distance.

While this method works well in most situations, it depends on the accuracy and frequency of the recorded GPS points. When the recorded points are inaccurate or poorly spaced, the calculated distance becomes inaccurate as well.

1. GPS Drift

One of the most common causes of incorrect distance is GPS drift. GPS drift occurs when your device slowly shifts position even though you are not actually moving. This can happen while standing still at a traffic light, waiting at a trail junction, or pausing during a workout.

When drift occurs, the device records a small wandering path around your actual position. Even though you stayed in one spot, the GPS track might form a small circle or zig-zag pattern. Because the device assumes every point represents movement, it adds that drift to your total distance.

This can easily add several hundred meters to a long activity.

Common situations where drift occurs:

• Waiting at intersections
• Pausing during workouts
• Standing still before starting the activity
• Recording indoors or under dense tree cover

How to avoid it:

• Pause the sports watch at an intersection, but remember to start it again

How to correct it after the run is completed:

• Use GpxFix to remove stationary time segments using the crop/cut feature
• Use GpxFix to smoothen the GPS track
• Use GpxFix to delete individual drifted track points using the edit track feature

2. Low GPS Sampling Rate

Another common reason for incorrect distance is low sampling frequency. Some devices record GPS points every second, while others record every few seconds to save battery.

If too few points are recorded, the track may cut corners or skip curves. This means the calculated path becomes shorter than the actual route you traveled.

For example, imagine running along a winding trail. If the GPS only records a point every 10 seconds, the track may draw straight lines between those points instead of following the true path. The result is a shorter distance.

Conversely, noisy signals combined with sparse sampling may produce jagged lines that increase distance.

How to avoid it:

• Change settings on your device to track evey seconds. Often this means disabling power save mode

How to correct activities that are too long:

• Use our 'Fix GPS issues' feature
• Use our GpxFix Smoothen track feature
• Use our resample feature
• Use the Change distance feature

How to correct activities that are too short:

• Use the GpxFix edit track points feature to drag individual track points to match your route
• Use the Change distance feature

3. GPS Signal Interference

GPS signals travel from satellites to your device. Anything that blocks or reflects those signals can reduce accuracy. This includes buildings, mountains, dense forests, and even your own body or your clothing.

In urban environments this is sometimes called the urban canyon effect. Tall buildings reflect GPS signals, causing the device to calculate incorrect positions.

When this happens your GPS track may jump sideways across streets, zig-zag between buildings, or drift off the road entirely. These jumps add extra distance that you never actually traveled.

Common interference environments:

• City centers with tall buildings
• Dense forests
• Deep valleys or mountains
• Tunnels and bridges
• Having your device inside a back pack or underneath thick clothing

How to correct it:

• Use our 'Fix GPS issues' feature
• Use the Smoothen track feature
• Edit incorrect coordinates manually

4. Pauses and Stationary Time

If you forget to pause your watch during a break, your device will continue recording movements.

Even when auto-pause features are enabled, they are not always perfect. Some devices still record slight motion while paused.

This often happens during:

• Coffee stops during rides
• Waiting for traffic lights
• Taking photos during hikes
• Group stops during races

How to correct it:

• Use our 'Remove still time' feature
• Use the Crop/cut feature to remove the paused section

5. GPS Spikes

Sometimes GPS devices produce extreme outliers called GPS spikes. A single point may suddenly jump hundreds of meters away and then immediately return to the correct path.

This produces a long triangular spike in the track. Because the distance calculation follows every point, the spike dramatically increases the recorded distance.

Spikes usually occur when the device briefly loses satellite lock.

How to correct it:

• Use our 'Fix GPS issues' feature to automatically remove the spike
• Replace them manually using the Edit cooredinates feature
• Replace bad segments using the 'Restore section' feature

6. Incorrect Elevation Data

Elevation errors normally affect climbing statistics, but they can also slightly influence distance calculations. Some systems include three-dimensional distance calculations that factor in elevation change.

If elevation data is noisy or incorrect, the calculated distance may become slightly inflated.

How to correct it:

• Auto fix elevation using our 'Calibrate elevation' feature

7. Device or Sensor Errors

Some devices supplement GPS with other sensors such as accelerometers or foot pods. These sensors estimate distance based on stride length or motion patterns.

If these sensors become miscalibrated, the device may incorrectly estimate distance, especially when GPS signal is weak.

Examples include:

• Incorrect stride calibration
• Foot pod misalignment
• Device firmware bugs
• Low battery conditions affecting GPS accuracy

These issues are less common but can still cause noticeable distance discrepancies.

How to Correct Distance in an Activity File

Fortunately, activity data can often be corrected after recording. If your GPX file contains errors, you can repair the track by editing or cleaning the GPS data.

Typical correction steps include:

1. Removing stationary segments that contain drift
2. Smoothing noisy GPS tracks
3. Deleting large GPS spikes
4. Resampling track points for better spacing
5. Correcting elevation data
6. Adjusting distance calculations

After fixing the track points, the total distance shown on GpxFix is recalculated using the cleaned data. In most cases this produces a distance much closer to the real route.

Tips for Recording More Accurate Activities

While errors can be corrected afterward, it’s always better to record cleaner data from the start. Here are some tips to improve GPS accuracy:

• Wait for full GPS signal lock before starting the activity
• Avoid starting recordings indoors
• Use high-accuracy recording modes when possible
• Pause your activity during long stops
• Keep device firmware updated

These steps can significantly reduce the likelihood of distance errors.

Final Thoughts

Incorrect activity distance is a common issue for runners, cyclists, and hikers. GPS drift, sampling limitations, signal interference, pauses, and device errors can all contribute to inaccurate recordings.

The good news is that most of these issues can be fixed by cleaning and correcting the GPS track. By removing drift, smoothing noisy data, and recalculating the track, you can restore your activity to a much more accurate representation of what actually happened.

With the right tools and a bit of understanding about how GPS works, your activity data can become far more reliable helping you track progress, compare efforts, and analyze performance with confidence.