Define the duplicate
Matching coordinates do not always mean matching points.
Two consecutive GPX points can have identical latitude and longitude while carrying different timestamps, elevations or extensions. They occupy the same horizontal position, but they are not necessarily duplicate observations. A stationary recorder, for example, can sample the same written coordinates at several times.
An exact XML duplicate repeats every relevant field. A positional duplicate repeats only latitude and longitude. A near duplicate has coordinates that differ slightly but represent effectively the same place at the scale of the activity.
That distinction matters before any clean-up. Deleting points solely because the coordinates match may also delete a pause, a sensor sample or a boundary between meaningful observations.
What they change
Zero horizontal movement can still carry time and height changes.
- Horizontal distanceTwo truly identical consecutive positions add no horizontal length between them.
- Elapsed timeDifferent timestamps still contribute an interval, which may represent waiting or a recorder continuing while stationary.
- Calculated speedZero distance over a positive interval yields a stationary sample. A zero-time interval needs guarded handling rather than division.
- Elevation gainDifferent elevation values at one horizontal position can add artificial climbing if every positive change is counted.
- File weightLarge runs of repeated points increase the document size and processing work without adding horizontal detail.
Near duplicates are more complicated. A cluster of tiny position changes can create distance while the person is still. This is usually a GPS-noise question rather than a duplicate-record question, and it belongs with GPS drift.
Common origins
Recording, conversion and editing can all repeat a point.
A receiver may output successive samples that round to the same decimal coordinates. A converter can duplicate the point at a boundary while joining two inputs. An editor may retain both the old and new copy after a split. Export software can also add a final point that repeats the previous position but closes a timing or sensor record.
GPX does not require adjacent points to be unique. Latitude and longitude must be valid, but the schema has no rule forbidding repeats. A validator can therefore accept a file containing thousands of identical points. Schema validity answers whether the structure follows GPX, not whether the sampling is useful.
A repeated coordinate is a symptom to inspect, not automatic permission to delete a record.
Clean-up
Decide which information must survive before removing anything.
- Copy
Keep the unedited file.
Duplicate removal changes the evidence in a recorded track, even when the visible map line stays still.
- Compare
Check every field on the repeated points.
Look at time, elevation, segment membership and extension data, not only latitude and longitude.
- Define
Choose a rule suited to the purpose.
A navigation-only copy can discard more timed detail than an activity archive should.
- Verify
Recalculate and inspect the result.
Confirm that distance, duration, elevation and segment boundaries still mean what you expect.
Sources & scope
What this answer is based on.
The schema defines required coordinates and optional point data but does not forbid repeats. The effect on summaries depends on the calculation applied by the receiving software.