How to tell if a recorded GPS track is accurate

The short answer

A recorded track is worth trusting when the line follows the shape of the ground you actually walked on, the distance and elevation are in a sensible range for that walk, and nothing on it looks physically impossible. It stops being trustworthy, at least in the affected stretch, when the line cuts through something you could not have walked through, or a number jumps to a value no person on foot could produce even for a moment.

The instinct to expect pixel-perfect agreement with the real trail is the wrong bar. GPS was never that precise, and a walk recorded on open ground with a clear view of the sky will still wander by a few metres here and there. The question worth asking is not "does this match exactly" but "does this look like what actually happened."

What "accurate" means underneath the map

Every position a phone reports comes with its own margin of error, even if no app shows you the number. Under open sky, that margin is typically a few metres. Under tree cover, between buildings, or in a narrow valley, satellite signals bounce off surfaces before reaching the receiver, and the margin can grow to tens of metres for as long as the conditions last. Nothing about this is a fault in a particular app — every device pulling a position from the same sky is working with the same physics.

A single point being a few metres off is invisible at the scale of a whole hike and never worth chasing. What actually matters is whether errors are small and scattered, which barely changes the shape of a long route, or whether something has gone wrong in a way that visibly distorts it.

Signs the track is worth trusting

• The line follows the trail itself on the map, not a straight line through a building, a lake, or open water where there was clearly no path.
• Distance is in a sensible range for the walk. It does not need to match a trailhead sign exactly — GPS distance is a sum of straight segments between points and a signposted figure is measured differently — but it should be in the same neighbourhood, not double or half.
• The elevation profile looks like a hill, with rises and falls that correspond to the terrain, not a jagged saw blade of noise on ground that was actually flat.
• There is no single point that jumps far off the rest of the line and back again in the space of one recorded position — a classic, easily explained spike rather than a stretch of genuinely bad data.

Signs of a real problem

A handful of things are worth actually looking into, rather than shrugging off as normal GPS wobble:

• A long stretch of the line that is dead straight across terrain nobody walks in a straight line across — usually a sign the receiver lost the sky for a while and the gap was bridged with a straight connector between the last good point and the next one, rather than a wrong reading at any single point.
• A pace figure that stays implausibly high for more than an instant, rather than spiking for one reading and settling back down — a momentary jump is ordinary GPS noise; a sustained one usually means something upstream of the app, such as a route with far too few points to describe what actually happened.
• A whole section of the walk with almost no recorded points at all, which usually lines up with a stretch of heavy tree cover, a narrow canyon, or a built-up area with tall buildings on both sides.

None of these mean the whole recording is worthless. They usually affect one stretch of a route, and the rest of the walk can still be trusted normally.

What denser points do not tell you

It is tempting to judge a track by how many points it has, but point count and accuracy are two different things. A recorder logs a new point when there is something new to report, which is driven mainly by whether you are moving, not by a fixed clock. A sparse but clean set of points draws a truer line than a dense but noisy one, so a lower point count on its own is not a red flag, and a high one is not a guarantee of quality either.

What to actually do about it

For an isolated spike, the fix is straightforward: the point is easy to identify against the rest of the line, and removing it — or editing the raw GPX file directly, since it is plain text — leaves the rest of the route untouched. For a whole stretch recorded under heavy cover or in a canyon, there usually is not a clean fix beyond accepting that the distance and elevation for that section are approximate, and comparing the walk against your own past recordings rather than expecting it to match a guidebook figure exactly.

What is rarely worth doing is re-recording a whole hike over a single dubious point. One good look at the line on a map, and a sanity check on the total distance and elevation, is usually enough to tell whether the rest of the recording is sound.

What TrailCam does

TrailCam reports distance, moving time, pace and elevation gain for every recorded route, drawn as a profile under the map. Because photos, video clips and voice notes are pinned to the exact spot on the route where they were captured, they double as a plain, human check on the line itself — if a clip filmed at a viewpoint sits where the viewpoint actually was, the surrounding stretch of track is doing its job. A route exports as GPX 1.1 or CSV, as part of the optional TrailCam Pro upgrade, for anyone who wants a closer look at the raw points themselves. It is free to download.