Documentation

Understanding track metrics

How distance, speed, moving time, elevation gain and gradient are calculated, and why values can differ between applications.

GPX Viewer calculates values from the positions and times in the file. It never invents measurements: a value the file does not contain stays empty.

Distance

The sum of the distances between consecutive points within each segment. A gap between segments adds nothing.

• The desktop applications measure each step on a sphere with the mean Earth radius (6,371,008.8 m).
• Web Lite measures each step on the WGS 84 ellipsoid (Vincenty’s formula).

The two methods differ by up to about 0.5 % depending on latitude and direction.

Time

• Elapsed time: from the earliest to the latest timestamp.
• Moving time: the sum of the steps, within one segment, that last more than 0 and at most 300 seconds and cover at least 0.5 m/s.
• Stopped time: elapsed time minus moving time.

Speed

• Calculated speed: the distance covered within about 5 seconds on each side of a point, divided by the time between them. It is never calculated across a recording gap, a segment break or a timestamp that goes backwards, and not over windows of 120 seconds or more.
• Recorded speed: the speed written by the device, shown separately when present.
• Average speed is distance over elapsed time; moving average is moving distance over moving time; maximum speed is the highest calculated speed.

Elevation gain and loss

Recorded elevation rises and falls by small amounts because of measurement noise. GPX Viewer counts a climb or descent only once the elevation has changed by at least the gain threshold from the last counted level: 5 m by default, or 2 m or 1 m. The level restarts in every segment. A lower threshold counts more of the noise, so it usually gives a higher gain.

The desktop applications can also use official terrain heights instead of the recorded elevation; each source keeps its own gain.

Gradient and vertical speed

• Gradient: the elevation, smoothed over 25 m on each side, compared over a centred 50 m window. It is not calculated where less than 40 % of the window is available.
• Vertical speed: the change of smoothed elevation over 30 seconds, in metres or feet per minute, within each segment.

Climbs

The desktop applications list climbs of at least 20 m at 3 % or more, starting where the route leaves the valley floor.

Recorded and calculated

Point details and graph tooltips label every value as recorded (from the file) or calculated (by GPX Viewer).

Updated 2026-10-25