GpxFix Blog

You Pressed Start Before the GPS Locked: How to Fix a Ruined First Kilometre

By Roy Lachica on October 16, 2026. Last updated October 16, 2026.

The activity opens with a long straight line from your front door, or from the car park, or from a hotel four streets away. Your first kilometre split says 2:14. Max speed for the whole run says 180 km/h. The distance is half a kilometre longer than the route you actually did. Nothing went wrong with your running, you simply pressed start a few seconds before the watch had worked out where it was, and those few seconds are now baked into the file.

What the device is doing while it is still searching

A GPS receiver needs several satellites and a few seconds of clean signal before it can state a position with any confidence. Press start before that happens and the device does not stop recording, it records the best position it has. That is usually one of three things: the last place it had a fix, which may be yesterday on the other side of town, a coarse position worked out from too few satellites, or a position estimated from cached satellite data that has gone stale.

So the file begins with points at a place you never were, timestamped from the moment you pressed start. When a real fix finally arrives, the position jumps to where you actually are. Everything that follows is good data. Everything before it is fiction, and the jump between the two is where the damage comes from.

What it breaks

• Max speed for the entire activity. A 400 metre jump between two points one second apart reads as roughly 1,400 km/h. Max speed is taken from the single fastest interval in the file, so one bad pair of points sets the number you see on the activity page.
• Distance. The phantom opening leg is added to your total, which is why the file reads long, see why your activity distance is wrong.
• The first split or lap. It absorbs the jump, so your opening kilometre looks either impossibly fast or wildly slow depending on which direction the error points.
• Segments near the start. A segment that begins in the first few hundred metres will not match, because your track did not come through its start the way the geometry expects, see why your Strava segment did not register.
• Elevation. A stale position usually carries a stale altitude, so the first points can add a climb or a drop that never happened.
• Average pace. Longer distance over the same time flatters your pace, which is the part people notice last and like the most, and it is still wrong.

Why the automatic fixes may leave the first point alone

This is the one GPS problem where reaching straight for the automatic pass is not the best first move, and it is worth understanding why. Spike detection looks for a point that jumps away from the track and then comes back, a detour that returns to the line. A bad start does not do that, it goes one way and stays there, because the rest of the recording is correct and it is the beginning that is displaced.

On top of that, the very first point of a file is treated as the anchor the rest of the track is measured against, so it survives the automatic clean-up even when the leg leading away from it is obviously impossible. The practical consequence: deal with the opening manually first, then run the automatic pass for everything else. Compare this with a freeze and jump in the middle of an activity, which the automatic tools handle well precisely because there is good data on both sides of it.

Find the first real point

1. Upload the file to GpxFix.
2. On the map, follow the straight line from the start, the point where it stops being a straight line and starts following the road is your first genuine position.
3. On the speed chart, the same moment is a single enormous spike in the first seconds. Select around it to read off the track point number.
4. Note that number, everything before it is what has to go or be moved.

Two ways to repair it

Crop the opening points

The simplest fix. Use Crop or cut and remove the range from the first track point up to the last bad one. The phantom distance, the speed spike and the stale elevation all disappear with those points. Two things change as a side effect, and both are expected: your activity now starts at the timestamp of the first remaining point, so the elapsed time shortens by however many seconds you cut, and your total distance drops. See the crop and cut guide.

Move the opening points onto the real start

If those seconds matter, for example because the activity has to start at the official race start time, use Edit coordinates instead. You reposition the bad points onto the place you actually were, keeping their timestamps, so the elapsed time and the start time stay exactly as recorded while the phantom distance goes away. It takes longer than cropping, and it is the better choice when the clock matters more than the convenience.

After either repair, run Fix GPS issues or Just fix it to deal with anything else in the file, and read the summary again to confirm distance and max speed are now plausible. If the opening is fine but the whole track sits in the wrong place, that is a different problem, see manually fixing a track that drifted far off course.

Is trimming the start legitimate

Yes, and note which direction it moves your numbers: removing a phantom opening leg makes your activity shorter and your average pace slower, which is the opposite of flattering. You are deleting distance you did not cover, see the ethics of editing fitness data. What is not legitimate is cropping a slow warm-up you genuinely ran in order to improve your average pace, that is editing performance rather than correcting a recording error.

Not pressing start too early next time

• Wait for the fix indicator to go solid, not just for the GPS screen to appear. Most watches distinguish searching from ready, and the difference is a few seconds.
• Sync the watch before you head out. Devices download predicted satellite data that expires after a few days, and a watch that has not synced takes far longer to find itself.
• Stand still in the open while it searches. Walking towards the start line while the receiver is still working it out is exactly how the phantom leg gets recorded.
• Do not search indoors, under a roof, in a car, or beside a building, then step out and press start immediately.
• Phone users, open the app a minute early rather than at the moment you want to start.
• In a race, get the fix in the start pen well before the gun, then press start as you cross the line.

More on recording clean data in the first place is in how to get accurate GPS and heart rate data.

Frequently asked questions

My watch said GPS was ready, so why did this still happen?

Ready can mean a coarse fix from the minimum number of satellites, which is enough to claim a position and not enough for that position to be right. Accuracy keeps improving for a while after the device says it is ready, which is why the first seconds of a recording are the least reliable part of it.

Does cropping the start change my activity start time?

Yes. The activity begins at the first track point that remains, so cutting 40 seconds off the front moves the start 40 seconds later and shortens elapsed time by the same amount. If you need the original start time, reposition the points instead, or set the time afterwards, see adjusting the start time of your activity.

Why is only the start wrong when the rest of the track is perfect?

Because the problem is a timing one, not a signal quality one. Once the receiver has a proper fix it keeps it, so the error is confined to the seconds before that happened.

Can I just leave it and let Strava sort it out?

Strava displays what the file contains, so the inflated distance and the impossible max speed stay. It also has no way of knowing which part of the opening was real.

Both the start and the end of my activity are junk

Common enough, the end usually being a recording that kept going after you finished, see forgot to stop your watch. Fix them in the same session, one crop at each end.

Got an activity that starts at your front door instead of the start line? Upload it to GpxFix, find where the straight line ends, and cut or move the points before it. Related reading: removing GPS spikes and snap to road.