TL;DR
This glossary is a set of neutral, practical definitions used across Drivurs Learn. It’s written so you can copy/paste a term into a chat, an event plan, or your own notes without arguing about jargon.
GPS fix
A GPS “fix” is the device’s current navigation solution: its best estimate of position (and often velocity) based on available satellite signals. Fix quality can change as conditions change (sky view, environment, motion).
Related: How accurate is GPS for racing apps?
2D fix vs 3D fix
Simplified:
- 2D fix: position estimate without reliable altitude.
- 3D fix: position estimate that includes altitude.
In practice, “3D” often correlates with a more complete solution, but your real goal is stable, repeatable telemetry under good sky view.
Telemetry
Telemetry is a time-series stream of measurements sent from a device to an app. In GPS-based timing workflows, telemetry typically includes speed and/or position samples at a given rate.
Related: How does drag timing work in GPS-based apps?
Sample rate
How often a device provides telemetry samples (for example, 10–25 times per second). Higher sample rate can improve smoothness and threshold detection, but it doesn’t compensate for poor sky view or unstable mounting.
Validation
Validation is the process of deciding whether a run is usable for comparison. A validated run typically requires:
- Readiness (usable fix + fresh telemetry)
- Repeatability (multiple similar runs)
- Controlled variables (same road/direction/setup)
Related: Performance tracking for cars
Run invalidation
A run becomes “invalid” when conditions make it unreliable for comparison (for example, missing telemetry, poor readiness, or other diagnostics that indicate the data is incomplete). Invalidation is a guardrail: it prevents “bad data” from being treated as truth.
Trap speed
Trap speed is a speed measurement near a distance finish line (for example, near the 1/4 mile marker). It’s used as a summary signal for how the car carried speed through the end of a run.
False start
A “false start” is when a run start is detected incorrectly (or triggered too early). In GPS timing workflows, start detection is often based on crossing a movement or speed threshold.
Drift (GPS drift)
GPS drift is slow movement or wobble in the reported position/speed estimate even when the real position is stable. Drift can increase under poor sky view, multipath (reflections), or unstable conditions.
Density altitude (high-level)
Density altitude is a concept used to describe how air density affects performance. Higher density altitude (thinner air) can reduce power for naturally aspirated engines. Treat it as “conditions changed” and avoid comparing runs across wildly different weather without context.
Common mistakes (terminology that causes confusion)
- Treating “GPS Ready” as “perfectly accurate” instead of “more comparable than before”
- Mixing up 0–60 time (a metric) with “validation” (a decision about usable data)
- Assuming higher sample rate fixes bad mounting or poor sky view
- Comparing trap speed and elapsed time without noting conditions and direction
- Using “telemetry” to mean “any screenshot” instead of time-series data over a run
Related guides
- Performance pillar: Performance tracking for cars
- Communities pillar: Car communities, clubs, and meets
- Ownership pillar: Managing a car build
- Same cluster: GPS timing apps vs track transponders
- Same cluster: Are car meets legal? What organizers need to know