Does a jagged elevation profile mean the recording is inaccurate?

Not on its own. The position track can be perfectly usable even while the height readings behind the profile carry their own small, separate margin of error, which is what produces the jagged look.

Will recording the same trail again give a smoother-looking profile?

Not reliably — a second recording carries its own independent scatter of small height errors, so the line will still look jagged, just with the little ups and downs falling in slightly different places.

Does a jagged profile affect the total elevation gain figure?

Yes, usually upward — an elevation gain total is built by adding up every upward step in the profile, so a noisier, spikier line tends to add up to a higher total than the trail's real climb.

Guides

Why does an elevation profile look jagged instead of smooth?

Open the elevation chart under a recorded route and the line rarely looks like the calm, even slope the walk felt like underfoot. Instead it saws up and down in short little steps, even on a trail with one steady grade and no real dips. Most of that jaggedness is not a sign that anything went wrong — it is what happens when a continuous, gently changing slope gets rebuilt from a series of separate height readings, each one carrying a small amount of its own noise.

The short answer

An elevation profile is drawn by connecting the height recorded at each point along the route, one after another. Each of those height readings is independently estimated and carries a small margin of error — a few metres either way — that has nothing to do with the real shape of the ground. String enough of those slightly-off points together and the line zigzags upward in little steps instead of rising as one clean slope, even when the actual trail underneath was a steady, unbroken climb.

Where the noise comes from

Working out height is a harder problem than working out position on a flat map. A GPS position is fixed by comparing signals from satellites spread out across the sky in every direction, which pins down latitude and longitude fairly tightly. Height depends on the same signals viewed from a much narrower range of angles, since every satellite in view sits somewhere above the horizon rather than below it, so the vertical estimate is inherently the shakier of the two numbers coming out of the same fix. A phone reading is also affected by nearby terrain, tree cover and how many satellites happen to be visible at that exact point, so the amount of noise is not even constant — it can tighten up in open country and loosen again under trees a few steps later.

None of this shows up as a single big error. It shows up as a steady scatter of small ones, a metre or two up, then a metre or two down, point after point — which is exactly the pattern that turns a smooth incline into a jagged line once it is drawn.

Some of the jaggedness is real

Not all of it is noise. A trail that looks like one steady climb from a trailhead sign or a map contour line is rarely a perfectly even ramp underfoot — a rooty section, a short rock step, a dip where the path crosses a dry creek bed, or a switchback that briefly loses and regains a few metres, all put genuine small ups and downs into the ground itself. A profile built from closely spaced points will pick up those real bumps as well as the GPS noise, and the two are not easy to tell apart just by looking at the chart. A trail that is genuinely rougher underfoot tends to produce a genuinely rougher-looking profile even with a perfect height reading at every point.

What a jagged profile does and does not tell you

A jagged line does not mean the recording failed or that the route is unreliable — the position track underneath it can be perfectly good even while the height column bounces around. It is also the same underlying noise responsible for elevation gain totals looking inflated on ground that was actually close to flat, since a gain figure is really just counting up every one of those small upward jogs in the line. Seeing a spiky profile is a reasonable explanation for a climb total that felt too high for how the walk actually felt, rather than a separate problem to chase down.

It also is not something a route can be walked around by trying harder. Walking the exact same line again would still produce a profile with its own scatter of small ups and downs, just not the same ones in the same places, because the noise comes from the measurement rather than from anything about how the trail was walked.

Where TrailCam fits in

TrailCam draws the elevation profile for every recorded route as a chart running underneath the map, built from the same points behind the distance and pace figures. The route exports as GPX 1.1 or CSV, so anyone curious can look at the raw elevation values behind the chart rather than taking the picture at face value. Export is part of the optional TrailCam Pro upgrade; the app itself is free to download.

Questions

Does a jagged elevation profile mean the recording is inaccurate?: Not on its own. The position track can be perfectly usable even while the height readings behind the profile carry their own small, separate margin of error, which is what produces the jagged look.
Will recording the same trail again give a smoother-looking profile?: Not reliably — a second recording carries its own independent scatter of small height errors, so the line will still look jagged, just with the little ups and downs falling in slightly different places.
Does a jagged profile affect the total elevation gain figure?: Yes, usually upward — an elevation gain total is built by adding up every upward step in the profile, so a noisier, spikier line tends to add up to a higher total than the trail's real climb.

Related guides

Recording your own routes

TrailCam is an iPhone app that records your route with GPS, keeps video clips, photos and voice notes pinned to the spot where you took them, and exports the result as GPX 1.1 or CSV. It is free to download.

Download on the App Store