GpxFix Blog

GPS Freezes Then Jumps: Why Your Watch Shows Impossible Speed Spikes

By Roy Lachica on August 22, 2026. Last updated August 22, 2026.

Your splits look ordinary but Strava flags a top speed of 180 km/h during a run, or your pace chart has a single spike that touches zero minutes per kilometer. Looking closer at the map, the route sits still in one spot for several points, then teleports a surprising distance to the next one. This is not a single bad GPS point, it is a recognizable pattern: the device freezes, then jumps. Here is why it happens and how it gets fixed without just deleting the affected minutes.

What the freeze-then-jump pattern looks like

Instead of one obviously wrong coordinate, you get a short run of points reporting almost no movement, the same or nearly the same latitude and longitude several times in a row, immediately followed by a point that has moved a large distance in the very next reported timestamp. Because the timestamp gap between the two points is small, GPS-derived speed for that single interval can spike to well over 100 km/h even during an easy run, since the calculation is simply distance divided by time, and the time was short while the reported distance was large.

Why a GPS receiver freezes and then catches up

• Temporary signal loss: passing under dense tree cover, between tall buildings, or under a bridge can cause the receiver to lose a confident fix. Rather than reporting nothing, some firmware keeps writing the last known position at each timestamp until a new fix locks in.
• Weak satellite geometry: in a narrow valley or urban canyon, the receiver may only see satellites clustered in one part of the sky, which degrades position accuracy without dropping the signal completely, producing a position that barely changes for a period.
• Recording buffer catch-up: some devices buffer position calculations and write several queued points back to the log in a short burst once a good fix returns, compressing what was actually a gradual movement into what looks like a single very fast jump.
• Cold start after a brief lock loss: if the receiver has to reacquire satellites from a near-cold state, the first fix after reacquisition can land a meaningful distance from where you actually are, correcting itself only on the following points.

Why this is not the same problem as a single GPS spike

A classic GPS spike is one rogue point flung far off the route, easy to spot and remove because the points immediately before and after it agree with each other. The freeze-then-jump pattern is different, it involves a cluster of points that individually look plausible, several stationary points followed by one that has moved a long way. Deleting the fast point alone would leave the stationary run in place and understate your distance and pace for that stretch, so it needs to be corrected as a group.

How GpxFix corrects it

GpxFix's GPS fixing pass looks specifically for this still-then-fast shape, not just isolated outliers. When it detects a run of near-stationary points followed by an implausibly fast one, it treats the whole cluster as a single distorted period and redistributes the movement more evenly across it, rather than either deleting the fast point or leaving the frozen points untouched. The result is a smoothed speed profile that better reflects what you were actually doing, typically bringing an artificial spike of well over 100 km/h down into a realistic range for the activity, while the total elevation gain for the affected stretch is left essentially unchanged.

Reducing how often this happens

• Keep the antenna side of the watch facing the sky where possible, a wrist turned palm-up under a jacket sleeve degrades reception more than most people expect.
• Enable multi-band or multi-constellation GPS (GPS plus GLONASS/Galileo) if your device supports it, more visible satellites means fewer total signal-loss events under cover.
• Update your device firmware, GPS chipset and buffering behavior are frequently improved in firmware updates from Garmin, COROS, and other manufacturers.
• Expect it under bridges, in tunnels of trees, and between tall buildings, and treat a single unrealistic spike on the map as a signal to check the GPS fixer rather than assume your watch actually recorded a sprint.

Frequently asked questions

Why does my run show an impossible top speed on Strava?

Almost always because two consecutive GPS points imply a large distance covered in a very short time, either from a single rogue point or from a frozen-then-jumping cluster like the one described here. It reflects a GPS artifact, not an actual burst of speed.

Will fixing this change my total distance?

Slightly, and usually downward, since the artificial jump was overstating distance for that interval. Redistributing the movement more evenly produces a total that is closer to what you actually covered.

Does this affect elevation gain too?

It can, if the jump also carried an elevation change, but GpxFix's fix targets the position and speed profile specifically and keeps elevation gain for the corrected section close to its original value.

If your speed chart has a spike that does not match how the run actually felt, open the file in GpxFix and let the automatic GPS fix take a look. Related reading: understanding GPS spike zones and removing GPS spikes.