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Define one trajectory and its time basis
The source dates shown in this guide identify documentation checks on 22 October 2026, while the cited records retain their stated publication dates. Start with feature id, timestamp format, timezone or UTC marker, coordinate array, altitude policy, and source sample status. A point recorded by a sensor, a point interpolated between samples, and a point generated by map matching are different evidence states.
| Field | Record | Stop if |
|---|---|---|
| Feature id | Stable trajectory identity | Id changes mid-path |
| Datetime | Exact string and normalized instant | Offset is discarded |
| Position | Coordinate order and dimensions | Axis order is assumed |
| Reference | WGS 84 or declared alternative | Projection is unnamed |
| Sample state | Observed, interpolated, or generated | Derived point looks observed |
| Coverage | Start, end, and missing intervals | Path length implies coverage |
Keep raw coordinates beside any normalized representation. The cited GeoJSON and trajectory requirements support a strict baseline for GeoJSON-like trajectories RFC Editor, (opens in a new tab) Open Geospatial Consortium, (opens in a new tab), but an owner still needs to describe capture method, expected sampling, and whether a point was withheld.
Measure sampling intervals before interpolation
Compute intervals between adjacent observed timestamps and record the expected cadence separately. A long interval is a gap finding, not permission to draw a straight line. Note duplicate or backward timestamps, bursts, pauses, and boundary gaps. If a trajectory uses variable sampling, report the distribution of intervals without compressing it into one average that hides outages.
| Sampling case | Evidence | Disposition |
|---|---|---|
| Regular | Expected cadence and observed deltas | Cadence matches within stated tolerance |
| Burst | Several points close together | Preserve raw sequence |
| Gap | No point across an interval | Hold interpolation decision |
| Duplicate time | Two positions at same instant | Owner rule required |
| Backward time | Timestamp less than predecessor | Ordering error or late arrival |
| Edge gap | Coverage boundary differs from request | Partial trajectory |
The cited trajectory requirements call for increasing datetimes with no repeated instant in a trajectory Open Geospatial Consortium, (opens in a new tab). If the source does not meet that rule, retain the raw sequence and report nonconformance rather than sorting and hiding the issue.
Separate coordinate semantics from path drawing
Record longitude and latitude in the order the format requires, then keep optional altitude and any engineering coordinate system in separate fields. Do not treat an easting and northing pair as ordinary GeoJSON longitude and latitude. State whether a line segment is a visual connection, a linear interpolation in time, or a path computed by another method.
- Validate coordinate array length and numeric order.
- Confirm the reference system and units from metadata.
- Compare coordinate and datetime counts.
- Mark all gaps and duplicate or backward instants.
- Record interpolation method and boundary assumptions.
- Keep interpolated points out of observed-point counts.
Use a synthetic trajectory fixture
Synthetic trajectory review
{"id":"fixture-route","coordinates":[[-73.0,40.0],[-72.9,40.1],[-72.7,40.2]],"datetimes":["2026-01-01T00:00:00Z","2026-01-01T00:05:00Z","2026-01-01T00:20:00Z"],"state":["observed","observed","observed"],"interpolation":"unresolved"}| Test | Expected result | Hold condition |
|---|---|---|
| Order | Longitude then latitude recorded | Axis order inferred from map |
| Counts | Three coordinates and three times | Arrays differ in length |
| Monotonicity | Times strictly increase | Duplicate or backward instant |
| Gap | Fifteen-minute interval flagged | Straight line called observed |
| State | All points explicitly observed | Derived point mixed in |
The fixture uses invented coordinates and times. Add an invalid axis-order example, an optional third altitude value, a duplicated datetime, and a missing start marker. The worksheet should return a stable format finding without attempting to transform or geocode anything.
Keep trajectory evidence separate from location conclusions
Trajectory review can document coordinate and temporal structure. It cannot establish a person’s location, route intent, positional accuracy, safety, or suitability for a use. Preserve the raw positions, timestamps, reference system, sampling notes, and derived paths as separate artifacts.
Pair this guide with GeoJSON coordinate and geometry review for static geometry and export timestamps and timezones for time provenance. After a supported non-health scope, authority to describe the collection, and a controlled trajectory packet are established, the qualified appraisal request path may be a preparation step. It does not geocode, transform coordinates, infer routes, create a quote, match a buyer, or grant a license.
Takeaways
- Record timestamp, coordinate order, reference system, and sample state together.
- Measure intervals and mark gaps before choosing interpolation.
- Keep longitude and latitude distinct from projected easting and northing.
- Require matching coordinate and datetime arrays for trajectory fixtures.
- Do not treat a rendered line as an observed path.